2002 lines
56 KiB
C
2002 lines
56 KiB
C
/* Conditional constant propagation pass for the GNU compiler.
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Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
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2010 Free Software Foundation, Inc.
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Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org>
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Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com>
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 3, or (at your option) any
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later version.
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GCC is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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/* Conditional constant propagation (CCP) is based on the SSA
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propagation engine (tree-ssa-propagate.c). Constant assignments of
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the form VAR = CST are propagated from the assignments into uses of
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VAR, which in turn may generate new constants. The simulation uses
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a four level lattice to keep track of constant values associated
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with SSA names. Given an SSA name V_i, it may take one of the
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following values:
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UNINITIALIZED -> the initial state of the value. This value
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is replaced with a correct initial value
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the first time the value is used, so the
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rest of the pass does not need to care about
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it. Using this value simplifies initialization
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of the pass, and prevents us from needlessly
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scanning statements that are never reached.
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UNDEFINED -> V_i is a local variable whose definition
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has not been processed yet. Therefore we
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don't yet know if its value is a constant
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or not.
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CONSTANT -> V_i has been found to hold a constant
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value C.
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VARYING -> V_i cannot take a constant value, or if it
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does, it is not possible to determine it
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at compile time.
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The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node:
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1- In ccp_visit_stmt, we are interested in assignments whose RHS
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evaluates into a constant and conditional jumps whose predicate
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evaluates into a boolean true or false. When an assignment of
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the form V_i = CONST is found, V_i's lattice value is set to
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CONSTANT and CONST is associated with it. This causes the
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propagation engine to add all the SSA edges coming out the
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assignment into the worklists, so that statements that use V_i
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can be visited.
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If the statement is a conditional with a constant predicate, we
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mark the outgoing edges as executable or not executable
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depending on the predicate's value. This is then used when
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visiting PHI nodes to know when a PHI argument can be ignored.
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2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the
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same constant C, then the LHS of the PHI is set to C. This
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evaluation is known as the "meet operation". Since one of the
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goals of this evaluation is to optimistically return constant
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values as often as possible, it uses two main short cuts:
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- If an argument is flowing in through a non-executable edge, it
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is ignored. This is useful in cases like this:
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if (PRED)
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a_9 = 3;
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else
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a_10 = 100;
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a_11 = PHI (a_9, a_10)
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If PRED is known to always evaluate to false, then we can
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assume that a_11 will always take its value from a_10, meaning
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that instead of consider it VARYING (a_9 and a_10 have
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different values), we can consider it CONSTANT 100.
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- If an argument has an UNDEFINED value, then it does not affect
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the outcome of the meet operation. If a variable V_i has an
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UNDEFINED value, it means that either its defining statement
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hasn't been visited yet or V_i has no defining statement, in
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which case the original symbol 'V' is being used
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uninitialized. Since 'V' is a local variable, the compiler
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may assume any initial value for it.
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After propagation, every variable V_i that ends up with a lattice
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value of CONSTANT will have the associated constant value in the
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array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for
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final substitution and folding.
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Constant propagation in stores and loads (STORE-CCP)
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----------------------------------------------------
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While CCP has all the logic to propagate constants in GIMPLE
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registers, it is missing the ability to associate constants with
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stores and loads (i.e., pointer dereferences, structures and
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global/aliased variables). We don't keep loads and stores in
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SSA, but we do build a factored use-def web for them (in the
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virtual operands).
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For instance, consider the following code fragment:
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struct A a;
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const int B = 42;
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void foo (int i)
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{
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if (i > 10)
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a.a = 42;
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else
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{
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a.b = 21;
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a.a = a.b + 21;
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}
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if (a.a != B)
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never_executed ();
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}
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We should be able to deduce that the predicate 'a.a != B' is always
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false. To achieve this, we associate constant values to the SSA
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names in the VDEF operands for each store. Additionally,
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since we also glob partial loads/stores with the base symbol, we
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also keep track of the memory reference where the constant value
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was stored (in the MEM_REF field of PROP_VALUE_T). For instance,
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# a_5 = VDEF <a_4>
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a.a = 2;
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# VUSE <a_5>
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x_3 = a.b;
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In the example above, CCP will associate value '2' with 'a_5', but
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it would be wrong to replace the load from 'a.b' with '2', because
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'2' had been stored into a.a.
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Note that the initial value of virtual operands is VARYING, not
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UNDEFINED. Consider, for instance global variables:
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int A;
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foo (int i)
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{
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if (i_3 > 10)
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A_4 = 3;
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# A_5 = PHI (A_4, A_2);
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# VUSE <A_5>
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A.0_6 = A;
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return A.0_6;
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}
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The value of A_2 cannot be assumed to be UNDEFINED, as it may have
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been defined outside of foo. If we were to assume it UNDEFINED, we
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would erroneously optimize the above into 'return 3;'.
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Though STORE-CCP is not too expensive, it does have to do more work
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than regular CCP, so it is only enabled at -O2. Both regular CCP
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and STORE-CCP use the exact same algorithm. The only distinction
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is that when doing STORE-CCP, the boolean variable DO_STORE_CCP is
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set to true. This affects the evaluation of statements and PHI
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nodes.
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References:
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Constant propagation with conditional branches,
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Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
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Building an Optimizing Compiler,
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Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
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Advanced Compiler Design and Implementation,
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Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "tree.h"
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#include "flags.h"
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#include "rtl.h"
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#include "tm_p.h"
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#include "ggc.h"
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#include "basic-block.h"
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#include "output.h"
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#include "expr.h"
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#include "function.h"
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#include "diagnostic.h"
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#include "timevar.h"
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#include "tree-dump.h"
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#include "tree-flow.h"
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#include "tree-pass.h"
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#include "tree-ssa-propagate.h"
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#include "value-prof.h"
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#include "langhooks.h"
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#include "target.h"
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#include "toplev.h"
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#include "dbgcnt.h"
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/* Possible lattice values. */
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typedef enum
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{
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UNINITIALIZED,
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UNDEFINED,
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CONSTANT,
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VARYING
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} ccp_lattice_t;
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/* Array of propagated constant values. After propagation,
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CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
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the constant is held in an SSA name representing a memory store
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(i.e., a VDEF), CONST_VAL[I].MEM_REF will contain the actual
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memory reference used to store (i.e., the LHS of the assignment
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doing the store). */
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static prop_value_t *const_val;
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static void canonicalize_float_value (prop_value_t *);
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static bool ccp_fold_stmt (gimple_stmt_iterator *);
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/* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
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static void
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dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val)
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{
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switch (val.lattice_val)
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{
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case UNINITIALIZED:
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fprintf (outf, "%sUNINITIALIZED", prefix);
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break;
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case UNDEFINED:
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fprintf (outf, "%sUNDEFINED", prefix);
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break;
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case VARYING:
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fprintf (outf, "%sVARYING", prefix);
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break;
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case CONSTANT:
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fprintf (outf, "%sCONSTANT ", prefix);
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print_generic_expr (outf, val.value, dump_flags);
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break;
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default:
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gcc_unreachable ();
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}
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}
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/* Print lattice value VAL to stderr. */
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void debug_lattice_value (prop_value_t val);
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void
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debug_lattice_value (prop_value_t val)
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{
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dump_lattice_value (stderr, "", val);
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fprintf (stderr, "\n");
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}
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/* Compute a default value for variable VAR and store it in the
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CONST_VAL array. The following rules are used to get default
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values:
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1- Global and static variables that are declared constant are
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considered CONSTANT.
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2- Any other value is considered UNDEFINED. This is useful when
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considering PHI nodes. PHI arguments that are undefined do not
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change the constant value of the PHI node, which allows for more
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constants to be propagated.
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3- Variables defined by statements other than assignments and PHI
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nodes are considered VARYING.
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4- Initial values of variables that are not GIMPLE registers are
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considered VARYING. */
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static prop_value_t
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get_default_value (tree var)
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{
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tree sym = SSA_NAME_VAR (var);
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prop_value_t val = { UNINITIALIZED, NULL_TREE };
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gimple stmt;
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stmt = SSA_NAME_DEF_STMT (var);
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if (gimple_nop_p (stmt))
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{
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/* Variables defined by an empty statement are those used
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before being initialized. If VAR is a local variable, we
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can assume initially that it is UNDEFINED, otherwise we must
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consider it VARYING. */
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if (is_gimple_reg (sym) && TREE_CODE (sym) != PARM_DECL)
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val.lattice_val = UNDEFINED;
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else
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val.lattice_val = VARYING;
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}
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else if (is_gimple_assign (stmt)
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/* Value-returning GIMPLE_CALL statements assign to
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a variable, and are treated similarly to GIMPLE_ASSIGN. */
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|| (is_gimple_call (stmt)
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&& gimple_call_lhs (stmt) != NULL_TREE)
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|| gimple_code (stmt) == GIMPLE_PHI)
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{
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tree cst;
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if (gimple_assign_single_p (stmt)
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&& DECL_P (gimple_assign_rhs1 (stmt))
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&& (cst = get_symbol_constant_value (gimple_assign_rhs1 (stmt))))
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{
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val.lattice_val = CONSTANT;
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val.value = cst;
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}
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else
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/* Any other variable defined by an assignment or a PHI node
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is considered UNDEFINED. */
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val.lattice_val = UNDEFINED;
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}
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else
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{
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/* Otherwise, VAR will never take on a constant value. */
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val.lattice_val = VARYING;
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}
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return val;
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}
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/* Get the constant value associated with variable VAR. */
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static inline prop_value_t *
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get_value (tree var)
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{
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prop_value_t *val;
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if (const_val == NULL)
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return NULL;
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val = &const_val[SSA_NAME_VERSION (var)];
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if (val->lattice_val == UNINITIALIZED)
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*val = get_default_value (var);
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canonicalize_float_value (val);
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return val;
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}
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/* Sets the value associated with VAR to VARYING. */
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static inline void
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set_value_varying (tree var)
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{
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prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
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val->lattice_val = VARYING;
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val->value = NULL_TREE;
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}
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/* For float types, modify the value of VAL to make ccp work correctly
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for non-standard values (-0, NaN):
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If HONOR_SIGNED_ZEROS is false, and VAL = -0, we canonicalize it to 0.
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If HONOR_NANS is false, and VAL is NaN, we canonicalize it to UNDEFINED.
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This is to fix the following problem (see PR 29921): Suppose we have
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x = 0.0 * y
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and we set value of y to NaN. This causes value of x to be set to NaN.
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When we later determine that y is in fact VARYING, fold uses the fact
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that HONOR_NANS is false, and we try to change the value of x to 0,
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causing an ICE. With HONOR_NANS being false, the real appearance of
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NaN would cause undefined behavior, though, so claiming that y (and x)
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are UNDEFINED initially is correct. */
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static void
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canonicalize_float_value (prop_value_t *val)
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{
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enum machine_mode mode;
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tree type;
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REAL_VALUE_TYPE d;
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if (val->lattice_val != CONSTANT
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|| TREE_CODE (val->value) != REAL_CST)
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return;
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d = TREE_REAL_CST (val->value);
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type = TREE_TYPE (val->value);
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mode = TYPE_MODE (type);
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if (!HONOR_SIGNED_ZEROS (mode)
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&& REAL_VALUE_MINUS_ZERO (d))
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{
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val->value = build_real (type, dconst0);
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return;
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}
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if (!HONOR_NANS (mode)
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&& REAL_VALUE_ISNAN (d))
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{
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val->lattice_val = UNDEFINED;
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val->value = NULL;
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return;
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}
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}
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/* Set the value for variable VAR to NEW_VAL. Return true if the new
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value is different from VAR's previous value. */
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static bool
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set_lattice_value (tree var, prop_value_t new_val)
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{
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prop_value_t *old_val = get_value (var);
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canonicalize_float_value (&new_val);
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/* Lattice transitions must always be monotonically increasing in
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value. If *OLD_VAL and NEW_VAL are the same, return false to
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inform the caller that this was a non-transition. */
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gcc_assert (old_val->lattice_val < new_val.lattice_val
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|| (old_val->lattice_val == new_val.lattice_val
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&& ((!old_val->value && !new_val.value)
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|| operand_equal_p (old_val->value, new_val.value, 0))));
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if (old_val->lattice_val != new_val.lattice_val)
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{
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if (dump_file && (dump_flags & TDF_DETAILS))
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{
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dump_lattice_value (dump_file, "Lattice value changed to ", new_val);
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fprintf (dump_file, ". Adding SSA edges to worklist.\n");
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}
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*old_val = new_val;
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gcc_assert (new_val.lattice_val != UNDEFINED);
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return true;
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}
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return false;
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}
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/* Return the likely CCP lattice value for STMT.
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If STMT has no operands, then return CONSTANT.
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Else if undefinedness of operands of STMT cause its value to be
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undefined, then return UNDEFINED.
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Else if any operands of STMT are constants, then return CONSTANT.
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Else return VARYING. */
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static ccp_lattice_t
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likely_value (gimple stmt)
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{
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bool has_constant_operand, has_undefined_operand, all_undefined_operands;
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tree use;
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ssa_op_iter iter;
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unsigned i;
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enum gimple_code code = gimple_code (stmt);
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/* This function appears to be called only for assignments, calls,
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conditionals, and switches, due to the logic in visit_stmt. */
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gcc_assert (code == GIMPLE_ASSIGN
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|| code == GIMPLE_CALL
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|| code == GIMPLE_COND
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|| code == GIMPLE_SWITCH);
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/* If the statement has volatile operands, it won't fold to a
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constant value. */
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if (gimple_has_volatile_ops (stmt))
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return VARYING;
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/* Arrive here for more complex cases. */
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has_constant_operand = false;
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has_undefined_operand = false;
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all_undefined_operands = true;
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FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
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{
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prop_value_t *val = get_value (use);
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if (val->lattice_val == UNDEFINED)
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has_undefined_operand = true;
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else
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all_undefined_operands = false;
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if (val->lattice_val == CONSTANT)
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has_constant_operand = true;
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}
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/* There may be constants in regular rhs operands. For calls we
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have to ignore lhs, fndecl and static chain, otherwise only
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the lhs. */
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for (i = (is_gimple_call (stmt) ? 2 : 0) + gimple_has_lhs (stmt);
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i < gimple_num_ops (stmt); ++i)
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{
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tree op = gimple_op (stmt, i);
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if (!op || TREE_CODE (op) == SSA_NAME)
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continue;
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if (is_gimple_min_invariant (op))
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has_constant_operand = true;
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}
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if (has_constant_operand)
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all_undefined_operands = false;
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/* If the operation combines operands like COMPLEX_EXPR make sure to
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not mark the result UNDEFINED if only one part of the result is
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undefined. */
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if (has_undefined_operand && all_undefined_operands)
|
|
return UNDEFINED;
|
|
else if (code == GIMPLE_ASSIGN && has_undefined_operand)
|
|
{
|
|
switch (gimple_assign_rhs_code (stmt))
|
|
{
|
|
/* Unary operators are handled with all_undefined_operands. */
|
|
case PLUS_EXPR:
|
|
case MINUS_EXPR:
|
|
case POINTER_PLUS_EXPR:
|
|
/* Not MIN_EXPR, MAX_EXPR. One VARYING operand may be selected.
|
|
Not bitwise operators, one VARYING operand may specify the
|
|
result completely. Not logical operators for the same reason.
|
|
Not COMPLEX_EXPR as one VARYING operand makes the result partly
|
|
not UNDEFINED. Not *DIV_EXPR, comparisons and shifts because
|
|
the undefined operand may be promoted. */
|
|
return UNDEFINED;
|
|
|
|
default:
|
|
;
|
|
}
|
|
}
|
|
/* If there was an UNDEFINED operand but the result may be not UNDEFINED
|
|
fall back to VARYING even if there were CONSTANT operands. */
|
|
if (has_undefined_operand)
|
|
return VARYING;
|
|
|
|
/* We do not consider virtual operands here -- load from read-only
|
|
memory may have only VARYING virtual operands, but still be
|
|
constant. */
|
|
if (has_constant_operand
|
|
|| gimple_references_memory_p (stmt))
|
|
return CONSTANT;
|
|
|
|
return VARYING;
|
|
}
|
|
|
|
/* Returns true if STMT cannot be constant. */
|
|
|
|
static bool
|
|
surely_varying_stmt_p (gimple stmt)
|
|
{
|
|
/* If the statement has operands that we cannot handle, it cannot be
|
|
constant. */
|
|
if (gimple_has_volatile_ops (stmt))
|
|
return true;
|
|
|
|
/* If it is a call and does not return a value or is not a
|
|
builtin and not an indirect call, it is varying. */
|
|
if (is_gimple_call (stmt))
|
|
{
|
|
tree fndecl;
|
|
if (!gimple_call_lhs (stmt)
|
|
|| ((fndecl = gimple_call_fndecl (stmt)) != NULL_TREE
|
|
&& !DECL_BUILT_IN (fndecl)))
|
|
return true;
|
|
}
|
|
|
|
/* Any other store operation is not interesting. */
|
|
else if (gimple_vdef (stmt))
|
|
return true;
|
|
|
|
/* Anything other than assignments and conditional jumps are not
|
|
interesting for CCP. */
|
|
if (gimple_code (stmt) != GIMPLE_ASSIGN
|
|
&& gimple_code (stmt) != GIMPLE_COND
|
|
&& gimple_code (stmt) != GIMPLE_SWITCH
|
|
&& gimple_code (stmt) != GIMPLE_CALL)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/* Initialize local data structures for CCP. */
|
|
|
|
static void
|
|
ccp_initialize (void)
|
|
{
|
|
basic_block bb;
|
|
|
|
const_val = XCNEWVEC (prop_value_t, num_ssa_names);
|
|
|
|
/* Initialize simulation flags for PHI nodes and statements. */
|
|
FOR_EACH_BB (bb)
|
|
{
|
|
gimple_stmt_iterator i;
|
|
|
|
for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
|
|
{
|
|
gimple stmt = gsi_stmt (i);
|
|
bool is_varying;
|
|
|
|
/* If the statement is a control insn, then we do not
|
|
want to avoid simulating the statement once. Failure
|
|
to do so means that those edges will never get added. */
|
|
if (stmt_ends_bb_p (stmt))
|
|
is_varying = false;
|
|
else
|
|
is_varying = surely_varying_stmt_p (stmt);
|
|
|
|
if (is_varying)
|
|
{
|
|
tree def;
|
|
ssa_op_iter iter;
|
|
|
|
/* If the statement will not produce a constant, mark
|
|
all its outputs VARYING. */
|
|
FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
|
|
set_value_varying (def);
|
|
}
|
|
prop_set_simulate_again (stmt, !is_varying);
|
|
}
|
|
}
|
|
|
|
/* Now process PHI nodes. We never clear the simulate_again flag on
|
|
phi nodes, since we do not know which edges are executable yet,
|
|
except for phi nodes for virtual operands when we do not do store ccp. */
|
|
FOR_EACH_BB (bb)
|
|
{
|
|
gimple_stmt_iterator i;
|
|
|
|
for (i = gsi_start_phis (bb); !gsi_end_p (i); gsi_next (&i))
|
|
{
|
|
gimple phi = gsi_stmt (i);
|
|
|
|
if (!is_gimple_reg (gimple_phi_result (phi)))
|
|
prop_set_simulate_again (phi, false);
|
|
else
|
|
prop_set_simulate_again (phi, true);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Debug count support. Reset the values of ssa names
|
|
VARYING when the total number ssa names analyzed is
|
|
beyond the debug count specified. */
|
|
|
|
static void
|
|
do_dbg_cnt (void)
|
|
{
|
|
unsigned i;
|
|
for (i = 0; i < num_ssa_names; i++)
|
|
{
|
|
if (!dbg_cnt (ccp))
|
|
{
|
|
const_val[i].lattice_val = VARYING;
|
|
const_val[i].value = NULL_TREE;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/* Do final substitution of propagated values, cleanup the flowgraph and
|
|
free allocated storage.
|
|
|
|
Return TRUE when something was optimized. */
|
|
|
|
static bool
|
|
ccp_finalize (void)
|
|
{
|
|
bool something_changed;
|
|
|
|
do_dbg_cnt ();
|
|
/* Perform substitutions based on the known constant values. */
|
|
something_changed = substitute_and_fold (const_val, ccp_fold_stmt);
|
|
|
|
free (const_val);
|
|
const_val = NULL;
|
|
return something_changed;;
|
|
}
|
|
|
|
|
|
/* Compute the meet operator between *VAL1 and *VAL2. Store the result
|
|
in VAL1.
|
|
|
|
any M UNDEFINED = any
|
|
any M VARYING = VARYING
|
|
Ci M Cj = Ci if (i == j)
|
|
Ci M Cj = VARYING if (i != j)
|
|
*/
|
|
|
|
static void
|
|
ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2)
|
|
{
|
|
if (val1->lattice_val == UNDEFINED)
|
|
{
|
|
/* UNDEFINED M any = any */
|
|
*val1 = *val2;
|
|
}
|
|
else if (val2->lattice_val == UNDEFINED)
|
|
{
|
|
/* any M UNDEFINED = any
|
|
Nothing to do. VAL1 already contains the value we want. */
|
|
;
|
|
}
|
|
else if (val1->lattice_val == VARYING
|
|
|| val2->lattice_val == VARYING)
|
|
{
|
|
/* any M VARYING = VARYING. */
|
|
val1->lattice_val = VARYING;
|
|
val1->value = NULL_TREE;
|
|
}
|
|
else if (val1->lattice_val == CONSTANT
|
|
&& val2->lattice_val == CONSTANT
|
|
&& simple_cst_equal (val1->value, val2->value) == 1)
|
|
{
|
|
/* Ci M Cj = Ci if (i == j)
|
|
Ci M Cj = VARYING if (i != j)
|
|
|
|
If these two values come from memory stores, make sure that
|
|
they come from the same memory reference. */
|
|
val1->lattice_val = CONSTANT;
|
|
val1->value = val1->value;
|
|
}
|
|
else
|
|
{
|
|
/* Any other combination is VARYING. */
|
|
val1->lattice_val = VARYING;
|
|
val1->value = NULL_TREE;
|
|
}
|
|
}
|
|
|
|
|
|
/* Loop through the PHI_NODE's parameters for BLOCK and compare their
|
|
lattice values to determine PHI_NODE's lattice value. The value of a
|
|
PHI node is determined calling ccp_lattice_meet with all the arguments
|
|
of the PHI node that are incoming via executable edges. */
|
|
|
|
static enum ssa_prop_result
|
|
ccp_visit_phi_node (gimple phi)
|
|
{
|
|
unsigned i;
|
|
prop_value_t *old_val, new_val;
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "\nVisiting PHI node: ");
|
|
print_gimple_stmt (dump_file, phi, 0, dump_flags);
|
|
}
|
|
|
|
old_val = get_value (gimple_phi_result (phi));
|
|
switch (old_val->lattice_val)
|
|
{
|
|
case VARYING:
|
|
return SSA_PROP_VARYING;
|
|
|
|
case CONSTANT:
|
|
new_val = *old_val;
|
|
break;
|
|
|
|
case UNDEFINED:
|
|
new_val.lattice_val = UNDEFINED;
|
|
new_val.value = NULL_TREE;
|
|
break;
|
|
|
|
default:
|
|
gcc_unreachable ();
|
|
}
|
|
|
|
for (i = 0; i < gimple_phi_num_args (phi); i++)
|
|
{
|
|
/* Compute the meet operator over all the PHI arguments flowing
|
|
through executable edges. */
|
|
edge e = gimple_phi_arg_edge (phi, i);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file,
|
|
"\n Argument #%d (%d -> %d %sexecutable)\n",
|
|
i, e->src->index, e->dest->index,
|
|
(e->flags & EDGE_EXECUTABLE) ? "" : "not ");
|
|
}
|
|
|
|
/* If the incoming edge is executable, Compute the meet operator for
|
|
the existing value of the PHI node and the current PHI argument. */
|
|
if (e->flags & EDGE_EXECUTABLE)
|
|
{
|
|
tree arg = gimple_phi_arg (phi, i)->def;
|
|
prop_value_t arg_val;
|
|
|
|
if (is_gimple_min_invariant (arg))
|
|
{
|
|
arg_val.lattice_val = CONSTANT;
|
|
arg_val.value = arg;
|
|
}
|
|
else
|
|
arg_val = *(get_value (arg));
|
|
|
|
ccp_lattice_meet (&new_val, &arg_val);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "\t");
|
|
print_generic_expr (dump_file, arg, dump_flags);
|
|
dump_lattice_value (dump_file, "\tValue: ", arg_val);
|
|
fprintf (dump_file, "\n");
|
|
}
|
|
|
|
if (new_val.lattice_val == VARYING)
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
|
|
fprintf (dump_file, "\n\n");
|
|
}
|
|
|
|
/* Make the transition to the new value. */
|
|
if (set_lattice_value (gimple_phi_result (phi), new_val))
|
|
{
|
|
if (new_val.lattice_val == VARYING)
|
|
return SSA_PROP_VARYING;
|
|
else
|
|
return SSA_PROP_INTERESTING;
|
|
}
|
|
else
|
|
return SSA_PROP_NOT_INTERESTING;
|
|
}
|
|
|
|
/* CCP specific front-end to the non-destructive constant folding
|
|
routines.
|
|
|
|
Attempt to simplify the RHS of STMT knowing that one or more
|
|
operands are constants.
|
|
|
|
If simplification is possible, return the simplified RHS,
|
|
otherwise return the original RHS or NULL_TREE. */
|
|
|
|
static tree
|
|
ccp_fold (gimple stmt)
|
|
{
|
|
location_t loc = gimple_location (stmt);
|
|
switch (gimple_code (stmt))
|
|
{
|
|
case GIMPLE_ASSIGN:
|
|
{
|
|
enum tree_code subcode = gimple_assign_rhs_code (stmt);
|
|
|
|
switch (get_gimple_rhs_class (subcode))
|
|
{
|
|
case GIMPLE_SINGLE_RHS:
|
|
{
|
|
tree rhs = gimple_assign_rhs1 (stmt);
|
|
enum tree_code_class kind = TREE_CODE_CLASS (subcode);
|
|
|
|
if (TREE_CODE (rhs) == SSA_NAME)
|
|
{
|
|
/* If the RHS is an SSA_NAME, return its known constant value,
|
|
if any. */
|
|
return get_value (rhs)->value;
|
|
}
|
|
/* Handle propagating invariant addresses into address operations.
|
|
The folding we do here matches that in tree-ssa-forwprop.c. */
|
|
else if (TREE_CODE (rhs) == ADDR_EXPR)
|
|
{
|
|
tree *base;
|
|
base = &TREE_OPERAND (rhs, 0);
|
|
while (handled_component_p (*base))
|
|
base = &TREE_OPERAND (*base, 0);
|
|
if (TREE_CODE (*base) == INDIRECT_REF
|
|
&& TREE_CODE (TREE_OPERAND (*base, 0)) == SSA_NAME)
|
|
{
|
|
prop_value_t *val = get_value (TREE_OPERAND (*base, 0));
|
|
if (val->lattice_val == CONSTANT
|
|
&& TREE_CODE (val->value) == ADDR_EXPR
|
|
&& may_propagate_address_into_dereference
|
|
(val->value, *base))
|
|
{
|
|
/* We need to return a new tree, not modify the IL
|
|
or share parts of it. So play some tricks to
|
|
avoid manually building it. */
|
|
tree ret, save = *base;
|
|
*base = TREE_OPERAND (val->value, 0);
|
|
ret = unshare_expr (rhs);
|
|
recompute_tree_invariant_for_addr_expr (ret);
|
|
*base = save;
|
|
return ret;
|
|
}
|
|
}
|
|
}
|
|
else if (TREE_CODE (rhs) == CONSTRUCTOR
|
|
&& TREE_CODE (TREE_TYPE (rhs)) == VECTOR_TYPE
|
|
&& (CONSTRUCTOR_NELTS (rhs)
|
|
== TYPE_VECTOR_SUBPARTS (TREE_TYPE (rhs))))
|
|
{
|
|
unsigned i;
|
|
tree val, list;
|
|
|
|
list = NULL_TREE;
|
|
FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (rhs), i, val)
|
|
{
|
|
if (TREE_CODE (val) == SSA_NAME
|
|
&& get_value (val)->lattice_val == CONSTANT)
|
|
val = get_value (val)->value;
|
|
if (TREE_CODE (val) == INTEGER_CST
|
|
|| TREE_CODE (val) == REAL_CST
|
|
|| TREE_CODE (val) == FIXED_CST)
|
|
list = tree_cons (NULL_TREE, val, list);
|
|
else
|
|
return NULL_TREE;
|
|
}
|
|
|
|
return build_vector (TREE_TYPE (rhs), nreverse (list));
|
|
}
|
|
|
|
if (kind == tcc_reference)
|
|
{
|
|
if ((TREE_CODE (rhs) == VIEW_CONVERT_EXPR
|
|
|| TREE_CODE (rhs) == REALPART_EXPR
|
|
|| TREE_CODE (rhs) == IMAGPART_EXPR)
|
|
&& TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
|
|
{
|
|
prop_value_t *val = get_value (TREE_OPERAND (rhs, 0));
|
|
if (val->lattice_val == CONSTANT)
|
|
return fold_unary_loc (EXPR_LOCATION (rhs),
|
|
TREE_CODE (rhs),
|
|
TREE_TYPE (rhs), val->value);
|
|
}
|
|
else if (TREE_CODE (rhs) == INDIRECT_REF
|
|
&& TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
|
|
{
|
|
prop_value_t *val = get_value (TREE_OPERAND (rhs, 0));
|
|
if (val->lattice_val == CONSTANT
|
|
&& TREE_CODE (val->value) == ADDR_EXPR
|
|
&& useless_type_conversion_p (TREE_TYPE (rhs),
|
|
TREE_TYPE (TREE_TYPE (val->value))))
|
|
rhs = TREE_OPERAND (val->value, 0);
|
|
}
|
|
return fold_const_aggregate_ref (rhs);
|
|
}
|
|
else if (kind == tcc_declaration)
|
|
return get_symbol_constant_value (rhs);
|
|
return rhs;
|
|
}
|
|
|
|
case GIMPLE_UNARY_RHS:
|
|
{
|
|
/* Handle unary operators that can appear in GIMPLE form.
|
|
Note that we know the single operand must be a constant,
|
|
so this should almost always return a simplified RHS. */
|
|
tree lhs = gimple_assign_lhs (stmt);
|
|
tree op0 = gimple_assign_rhs1 (stmt);
|
|
|
|
/* Simplify the operand down to a constant. */
|
|
if (TREE_CODE (op0) == SSA_NAME)
|
|
{
|
|
prop_value_t *val = get_value (op0);
|
|
if (val->lattice_val == CONSTANT)
|
|
op0 = get_value (op0)->value;
|
|
}
|
|
|
|
/* Conversions are useless for CCP purposes if they are
|
|
value-preserving. Thus the restrictions that
|
|
useless_type_conversion_p places for pointer type conversions
|
|
do not apply here. Substitution later will only substitute to
|
|
allowed places. */
|
|
if (CONVERT_EXPR_CODE_P (subcode)
|
|
&& POINTER_TYPE_P (TREE_TYPE (lhs))
|
|
&& POINTER_TYPE_P (TREE_TYPE (op0))
|
|
/* Do not allow differences in volatile qualification
|
|
as this might get us confused as to whether a
|
|
propagation destination statement is volatile
|
|
or not. See PR36988. */
|
|
&& (TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (lhs)))
|
|
== TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (op0)))))
|
|
{
|
|
tree tem;
|
|
/* Still try to generate a constant of correct type. */
|
|
if (!useless_type_conversion_p (TREE_TYPE (lhs),
|
|
TREE_TYPE (op0))
|
|
&& ((tem = maybe_fold_offset_to_address
|
|
(loc,
|
|
op0, integer_zero_node, TREE_TYPE (lhs)))
|
|
!= NULL_TREE))
|
|
return tem;
|
|
return op0;
|
|
}
|
|
|
|
return
|
|
fold_unary_ignore_overflow_loc (loc, subcode,
|
|
gimple_expr_type (stmt), op0);
|
|
}
|
|
|
|
case GIMPLE_BINARY_RHS:
|
|
{
|
|
/* Handle binary operators that can appear in GIMPLE form. */
|
|
tree op0 = gimple_assign_rhs1 (stmt);
|
|
tree op1 = gimple_assign_rhs2 (stmt);
|
|
|
|
/* Simplify the operands down to constants when appropriate. */
|
|
if (TREE_CODE (op0) == SSA_NAME)
|
|
{
|
|
prop_value_t *val = get_value (op0);
|
|
if (val->lattice_val == CONSTANT)
|
|
op0 = val->value;
|
|
}
|
|
|
|
if (TREE_CODE (op1) == SSA_NAME)
|
|
{
|
|
prop_value_t *val = get_value (op1);
|
|
if (val->lattice_val == CONSTANT)
|
|
op1 = val->value;
|
|
}
|
|
|
|
/* Fold &foo + CST into an invariant reference if possible. */
|
|
if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
|
|
&& TREE_CODE (op0) == ADDR_EXPR
|
|
&& TREE_CODE (op1) == INTEGER_CST)
|
|
{
|
|
tree tem = maybe_fold_offset_to_address
|
|
(loc, op0, op1, TREE_TYPE (op0));
|
|
if (tem != NULL_TREE)
|
|
return tem;
|
|
}
|
|
|
|
return fold_binary_loc (loc, subcode,
|
|
gimple_expr_type (stmt), op0, op1);
|
|
}
|
|
|
|
default:
|
|
gcc_unreachable ();
|
|
}
|
|
}
|
|
break;
|
|
|
|
case GIMPLE_CALL:
|
|
{
|
|
tree fn = gimple_call_fn (stmt);
|
|
prop_value_t *val;
|
|
|
|
if (TREE_CODE (fn) == SSA_NAME)
|
|
{
|
|
val = get_value (fn);
|
|
if (val->lattice_val == CONSTANT)
|
|
fn = val->value;
|
|
}
|
|
if (TREE_CODE (fn) == ADDR_EXPR
|
|
&& TREE_CODE (TREE_OPERAND (fn, 0)) == FUNCTION_DECL
|
|
&& DECL_BUILT_IN (TREE_OPERAND (fn, 0)))
|
|
{
|
|
tree *args = XALLOCAVEC (tree, gimple_call_num_args (stmt));
|
|
tree call, retval;
|
|
unsigned i;
|
|
for (i = 0; i < gimple_call_num_args (stmt); ++i)
|
|
{
|
|
args[i] = gimple_call_arg (stmt, i);
|
|
if (TREE_CODE (args[i]) == SSA_NAME)
|
|
{
|
|
val = get_value (args[i]);
|
|
if (val->lattice_val == CONSTANT)
|
|
args[i] = val->value;
|
|
}
|
|
}
|
|
call = build_call_array_loc (loc,
|
|
gimple_call_return_type (stmt),
|
|
fn, gimple_call_num_args (stmt), args);
|
|
retval = fold_call_expr (EXPR_LOCATION (call), call, false);
|
|
if (retval)
|
|
/* fold_call_expr wraps the result inside a NOP_EXPR. */
|
|
STRIP_NOPS (retval);
|
|
return retval;
|
|
}
|
|
return NULL_TREE;
|
|
}
|
|
|
|
case GIMPLE_COND:
|
|
{
|
|
/* Handle comparison operators that can appear in GIMPLE form. */
|
|
tree op0 = gimple_cond_lhs (stmt);
|
|
tree op1 = gimple_cond_rhs (stmt);
|
|
enum tree_code code = gimple_cond_code (stmt);
|
|
|
|
/* Simplify the operands down to constants when appropriate. */
|
|
if (TREE_CODE (op0) == SSA_NAME)
|
|
{
|
|
prop_value_t *val = get_value (op0);
|
|
if (val->lattice_val == CONSTANT)
|
|
op0 = val->value;
|
|
}
|
|
|
|
if (TREE_CODE (op1) == SSA_NAME)
|
|
{
|
|
prop_value_t *val = get_value (op1);
|
|
if (val->lattice_val == CONSTANT)
|
|
op1 = val->value;
|
|
}
|
|
|
|
return fold_binary_loc (loc, code, boolean_type_node, op0, op1);
|
|
}
|
|
|
|
case GIMPLE_SWITCH:
|
|
{
|
|
tree rhs = gimple_switch_index (stmt);
|
|
|
|
if (TREE_CODE (rhs) == SSA_NAME)
|
|
{
|
|
/* If the RHS is an SSA_NAME, return its known constant value,
|
|
if any. */
|
|
return get_value (rhs)->value;
|
|
}
|
|
|
|
return rhs;
|
|
}
|
|
|
|
default:
|
|
gcc_unreachable ();
|
|
}
|
|
}
|
|
|
|
|
|
/* Return the tree representing the element referenced by T if T is an
|
|
ARRAY_REF or COMPONENT_REF into constant aggregates. Return
|
|
NULL_TREE otherwise. */
|
|
|
|
tree
|
|
fold_const_aggregate_ref (tree t)
|
|
{
|
|
prop_value_t *value;
|
|
tree base, ctor, idx, field;
|
|
unsigned HOST_WIDE_INT cnt;
|
|
tree cfield, cval;
|
|
|
|
if (TREE_CODE_CLASS (TREE_CODE (t)) == tcc_declaration)
|
|
return get_symbol_constant_value (t);
|
|
|
|
switch (TREE_CODE (t))
|
|
{
|
|
case ARRAY_REF:
|
|
/* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
|
|
DECL_INITIAL. If BASE is a nested reference into another
|
|
ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
|
|
the inner reference. */
|
|
base = TREE_OPERAND (t, 0);
|
|
switch (TREE_CODE (base))
|
|
{
|
|
case VAR_DECL:
|
|
if (!TREE_READONLY (base)
|
|
|| TREE_CODE (TREE_TYPE (base)) != ARRAY_TYPE
|
|
|| !targetm.binds_local_p (base))
|
|
return NULL_TREE;
|
|
|
|
ctor = DECL_INITIAL (base);
|
|
break;
|
|
|
|
case ARRAY_REF:
|
|
case COMPONENT_REF:
|
|
ctor = fold_const_aggregate_ref (base);
|
|
break;
|
|
|
|
case STRING_CST:
|
|
case CONSTRUCTOR:
|
|
ctor = base;
|
|
break;
|
|
|
|
default:
|
|
return NULL_TREE;
|
|
}
|
|
|
|
if (ctor == NULL_TREE
|
|
|| (TREE_CODE (ctor) != CONSTRUCTOR
|
|
&& TREE_CODE (ctor) != STRING_CST)
|
|
|| !TREE_STATIC (ctor))
|
|
return NULL_TREE;
|
|
|
|
/* Get the index. If we have an SSA_NAME, try to resolve it
|
|
with the current lattice value for the SSA_NAME. */
|
|
idx = TREE_OPERAND (t, 1);
|
|
switch (TREE_CODE (idx))
|
|
{
|
|
case SSA_NAME:
|
|
if ((value = get_value (idx))
|
|
&& value->lattice_val == CONSTANT
|
|
&& TREE_CODE (value->value) == INTEGER_CST)
|
|
idx = value->value;
|
|
else
|
|
return NULL_TREE;
|
|
break;
|
|
|
|
case INTEGER_CST:
|
|
break;
|
|
|
|
default:
|
|
return NULL_TREE;
|
|
}
|
|
|
|
/* Fold read from constant string. */
|
|
if (TREE_CODE (ctor) == STRING_CST)
|
|
{
|
|
if ((TYPE_MODE (TREE_TYPE (t))
|
|
== TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
|
|
&& (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
|
|
== MODE_INT)
|
|
&& GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1
|
|
&& compare_tree_int (idx, TREE_STRING_LENGTH (ctor)) < 0)
|
|
return build_int_cst_type (TREE_TYPE (t),
|
|
(TREE_STRING_POINTER (ctor)
|
|
[TREE_INT_CST_LOW (idx)]));
|
|
return NULL_TREE;
|
|
}
|
|
|
|
/* Whoo-hoo! I'll fold ya baby. Yeah! */
|
|
FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
|
|
if (tree_int_cst_equal (cfield, idx))
|
|
{
|
|
STRIP_NOPS (cval);
|
|
if (TREE_CODE (cval) == ADDR_EXPR)
|
|
{
|
|
tree base = get_base_address (TREE_OPERAND (cval, 0));
|
|
if (base && TREE_CODE (base) == VAR_DECL)
|
|
add_referenced_var (base);
|
|
}
|
|
return cval;
|
|
}
|
|
break;
|
|
|
|
case COMPONENT_REF:
|
|
/* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
|
|
DECL_INITIAL. If BASE is a nested reference into another
|
|
ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
|
|
the inner reference. */
|
|
base = TREE_OPERAND (t, 0);
|
|
switch (TREE_CODE (base))
|
|
{
|
|
case VAR_DECL:
|
|
if (!TREE_READONLY (base)
|
|
|| TREE_CODE (TREE_TYPE (base)) != RECORD_TYPE
|
|
|| !targetm.binds_local_p (base))
|
|
return NULL_TREE;
|
|
|
|
ctor = DECL_INITIAL (base);
|
|
break;
|
|
|
|
case ARRAY_REF:
|
|
case COMPONENT_REF:
|
|
ctor = fold_const_aggregate_ref (base);
|
|
break;
|
|
|
|
default:
|
|
return NULL_TREE;
|
|
}
|
|
|
|
if (ctor == NULL_TREE
|
|
|| TREE_CODE (ctor) != CONSTRUCTOR
|
|
|| !TREE_STATIC (ctor))
|
|
return NULL_TREE;
|
|
|
|
field = TREE_OPERAND (t, 1);
|
|
|
|
FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
|
|
if (cfield == field
|
|
/* FIXME: Handle bit-fields. */
|
|
&& ! DECL_BIT_FIELD (cfield))
|
|
{
|
|
STRIP_NOPS (cval);
|
|
if (TREE_CODE (cval) == ADDR_EXPR)
|
|
{
|
|
tree base = get_base_address (TREE_OPERAND (cval, 0));
|
|
if (base && TREE_CODE (base) == VAR_DECL)
|
|
add_referenced_var (base);
|
|
}
|
|
return cval;
|
|
}
|
|
break;
|
|
|
|
case REALPART_EXPR:
|
|
case IMAGPART_EXPR:
|
|
{
|
|
tree c = fold_const_aggregate_ref (TREE_OPERAND (t, 0));
|
|
if (c && TREE_CODE (c) == COMPLEX_CST)
|
|
return fold_build1_loc (EXPR_LOCATION (t),
|
|
TREE_CODE (t), TREE_TYPE (t), c);
|
|
break;
|
|
}
|
|
|
|
case INDIRECT_REF:
|
|
{
|
|
tree base = TREE_OPERAND (t, 0);
|
|
if (TREE_CODE (base) == SSA_NAME
|
|
&& (value = get_value (base))
|
|
&& value->lattice_val == CONSTANT
|
|
&& TREE_CODE (value->value) == ADDR_EXPR
|
|
&& useless_type_conversion_p (TREE_TYPE (t),
|
|
TREE_TYPE (TREE_TYPE (value->value))))
|
|
return fold_const_aggregate_ref (TREE_OPERAND (value->value, 0));
|
|
break;
|
|
}
|
|
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return NULL_TREE;
|
|
}
|
|
|
|
/* Evaluate statement STMT.
|
|
Valid only for assignments, calls, conditionals, and switches. */
|
|
|
|
static prop_value_t
|
|
evaluate_stmt (gimple stmt)
|
|
{
|
|
prop_value_t val;
|
|
tree simplified = NULL_TREE;
|
|
ccp_lattice_t likelyvalue = likely_value (stmt);
|
|
bool is_constant;
|
|
|
|
fold_defer_overflow_warnings ();
|
|
|
|
/* If the statement is likely to have a CONSTANT result, then try
|
|
to fold the statement to determine the constant value. */
|
|
/* FIXME. This is the only place that we call ccp_fold.
|
|
Since likely_value never returns CONSTANT for calls, we will
|
|
not attempt to fold them, including builtins that may profit. */
|
|
if (likelyvalue == CONSTANT)
|
|
simplified = ccp_fold (stmt);
|
|
/* If the statement is likely to have a VARYING result, then do not
|
|
bother folding the statement. */
|
|
else if (likelyvalue == VARYING)
|
|
{
|
|
enum gimple_code code = gimple_code (stmt);
|
|
if (code == GIMPLE_ASSIGN)
|
|
{
|
|
enum tree_code subcode = gimple_assign_rhs_code (stmt);
|
|
|
|
/* Other cases cannot satisfy is_gimple_min_invariant
|
|
without folding. */
|
|
if (get_gimple_rhs_class (subcode) == GIMPLE_SINGLE_RHS)
|
|
simplified = gimple_assign_rhs1 (stmt);
|
|
}
|
|
else if (code == GIMPLE_SWITCH)
|
|
simplified = gimple_switch_index (stmt);
|
|
else
|
|
/* These cannot satisfy is_gimple_min_invariant without folding. */
|
|
gcc_assert (code == GIMPLE_CALL || code == GIMPLE_COND);
|
|
}
|
|
|
|
is_constant = simplified && is_gimple_min_invariant (simplified);
|
|
|
|
fold_undefer_overflow_warnings (is_constant, stmt, 0);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "which is likely ");
|
|
switch (likelyvalue)
|
|
{
|
|
case CONSTANT:
|
|
fprintf (dump_file, "CONSTANT");
|
|
break;
|
|
case UNDEFINED:
|
|
fprintf (dump_file, "UNDEFINED");
|
|
break;
|
|
case VARYING:
|
|
fprintf (dump_file, "VARYING");
|
|
break;
|
|
default:;
|
|
}
|
|
fprintf (dump_file, "\n");
|
|
}
|
|
|
|
if (is_constant)
|
|
{
|
|
/* The statement produced a constant value. */
|
|
val.lattice_val = CONSTANT;
|
|
val.value = simplified;
|
|
}
|
|
else
|
|
{
|
|
/* The statement produced a nonconstant value. If the statement
|
|
had UNDEFINED operands, then the result of the statement
|
|
should be UNDEFINED. Otherwise, the statement is VARYING. */
|
|
if (likelyvalue == UNDEFINED)
|
|
val.lattice_val = likelyvalue;
|
|
else
|
|
val.lattice_val = VARYING;
|
|
|
|
val.value = NULL_TREE;
|
|
}
|
|
|
|
return val;
|
|
}
|
|
|
|
/* Fold the stmt at *GSI with CCP specific information that propagating
|
|
and regular folding does not catch. */
|
|
|
|
static bool
|
|
ccp_fold_stmt (gimple_stmt_iterator *gsi)
|
|
{
|
|
gimple stmt = gsi_stmt (*gsi);
|
|
|
|
switch (gimple_code (stmt))
|
|
{
|
|
case GIMPLE_COND:
|
|
{
|
|
prop_value_t val;
|
|
/* Statement evaluation will handle type mismatches in constants
|
|
more gracefully than the final propagation. This allows us to
|
|
fold more conditionals here. */
|
|
val = evaluate_stmt (stmt);
|
|
if (val.lattice_val != CONSTANT
|
|
|| TREE_CODE (val.value) != INTEGER_CST)
|
|
return false;
|
|
|
|
if (integer_zerop (val.value))
|
|
gimple_cond_make_false (stmt);
|
|
else
|
|
gimple_cond_make_true (stmt);
|
|
|
|
return true;
|
|
}
|
|
|
|
case GIMPLE_CALL:
|
|
{
|
|
tree lhs = gimple_call_lhs (stmt);
|
|
prop_value_t *val;
|
|
tree argt;
|
|
bool changed = false;
|
|
unsigned i;
|
|
|
|
/* If the call was folded into a constant make sure it goes
|
|
away even if we cannot propagate into all uses because of
|
|
type issues. */
|
|
if (lhs
|
|
&& TREE_CODE (lhs) == SSA_NAME
|
|
&& (val = get_value (lhs))
|
|
&& val->lattice_val == CONSTANT)
|
|
{
|
|
tree new_rhs = unshare_expr (val->value);
|
|
bool res;
|
|
if (!useless_type_conversion_p (TREE_TYPE (lhs),
|
|
TREE_TYPE (new_rhs)))
|
|
new_rhs = fold_convert (TREE_TYPE (lhs), new_rhs);
|
|
res = update_call_from_tree (gsi, new_rhs);
|
|
gcc_assert (res);
|
|
return true;
|
|
}
|
|
|
|
/* Propagate into the call arguments. Compared to replace_uses_in
|
|
this can use the argument slot types for type verification
|
|
instead of the current argument type. We also can safely
|
|
drop qualifiers here as we are dealing with constants anyway. */
|
|
argt = TYPE_ARG_TYPES (TREE_TYPE (TREE_TYPE (gimple_call_fn (stmt))));
|
|
for (i = 0; i < gimple_call_num_args (stmt) && argt;
|
|
++i, argt = TREE_CHAIN (argt))
|
|
{
|
|
tree arg = gimple_call_arg (stmt, i);
|
|
if (TREE_CODE (arg) == SSA_NAME
|
|
&& (val = get_value (arg))
|
|
&& val->lattice_val == CONSTANT
|
|
&& useless_type_conversion_p
|
|
(TYPE_MAIN_VARIANT (TREE_VALUE (argt)),
|
|
TYPE_MAIN_VARIANT (TREE_TYPE (val->value))))
|
|
{
|
|
gimple_call_set_arg (stmt, i, unshare_expr (val->value));
|
|
changed = true;
|
|
}
|
|
}
|
|
|
|
return changed;
|
|
}
|
|
|
|
case GIMPLE_ASSIGN:
|
|
{
|
|
tree lhs = gimple_assign_lhs (stmt);
|
|
prop_value_t *val;
|
|
|
|
/* If we have a load that turned out to be constant replace it
|
|
as we cannot propagate into all uses in all cases. */
|
|
if (gimple_assign_single_p (stmt)
|
|
&& TREE_CODE (lhs) == SSA_NAME
|
|
&& (val = get_value (lhs))
|
|
&& val->lattice_val == CONSTANT)
|
|
{
|
|
tree rhs = unshare_expr (val->value);
|
|
if (!useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (rhs)))
|
|
rhs = fold_convert (TREE_TYPE (lhs), rhs);
|
|
gimple_assign_set_rhs_from_tree (gsi, rhs);
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
|
|
/* Visit the assignment statement STMT. Set the value of its LHS to the
|
|
value computed by the RHS and store LHS in *OUTPUT_P. If STMT
|
|
creates virtual definitions, set the value of each new name to that
|
|
of the RHS (if we can derive a constant out of the RHS).
|
|
Value-returning call statements also perform an assignment, and
|
|
are handled here. */
|
|
|
|
static enum ssa_prop_result
|
|
visit_assignment (gimple stmt, tree *output_p)
|
|
{
|
|
prop_value_t val;
|
|
enum ssa_prop_result retval;
|
|
|
|
tree lhs = gimple_get_lhs (stmt);
|
|
|
|
gcc_assert (gimple_code (stmt) != GIMPLE_CALL
|
|
|| gimple_call_lhs (stmt) != NULL_TREE);
|
|
|
|
if (gimple_assign_copy_p (stmt))
|
|
{
|
|
tree rhs = gimple_assign_rhs1 (stmt);
|
|
|
|
if (TREE_CODE (rhs) == SSA_NAME)
|
|
{
|
|
/* For a simple copy operation, we copy the lattice values. */
|
|
prop_value_t *nval = get_value (rhs);
|
|
val = *nval;
|
|
}
|
|
else
|
|
val = evaluate_stmt (stmt);
|
|
}
|
|
else
|
|
/* Evaluate the statement, which could be
|
|
either a GIMPLE_ASSIGN or a GIMPLE_CALL. */
|
|
val = evaluate_stmt (stmt);
|
|
|
|
retval = SSA_PROP_NOT_INTERESTING;
|
|
|
|
/* Set the lattice value of the statement's output. */
|
|
if (TREE_CODE (lhs) == SSA_NAME)
|
|
{
|
|
/* If STMT is an assignment to an SSA_NAME, we only have one
|
|
value to set. */
|
|
if (set_lattice_value (lhs, val))
|
|
{
|
|
*output_p = lhs;
|
|
if (val.lattice_val == VARYING)
|
|
retval = SSA_PROP_VARYING;
|
|
else
|
|
retval = SSA_PROP_INTERESTING;
|
|
}
|
|
}
|
|
|
|
return retval;
|
|
}
|
|
|
|
|
|
/* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
|
|
if it can determine which edge will be taken. Otherwise, return
|
|
SSA_PROP_VARYING. */
|
|
|
|
static enum ssa_prop_result
|
|
visit_cond_stmt (gimple stmt, edge *taken_edge_p)
|
|
{
|
|
prop_value_t val;
|
|
basic_block block;
|
|
|
|
block = gimple_bb (stmt);
|
|
val = evaluate_stmt (stmt);
|
|
|
|
/* Find which edge out of the conditional block will be taken and add it
|
|
to the worklist. If no single edge can be determined statically,
|
|
return SSA_PROP_VARYING to feed all the outgoing edges to the
|
|
propagation engine. */
|
|
*taken_edge_p = val.value ? find_taken_edge (block, val.value) : 0;
|
|
if (*taken_edge_p)
|
|
return SSA_PROP_INTERESTING;
|
|
else
|
|
return SSA_PROP_VARYING;
|
|
}
|
|
|
|
|
|
/* Evaluate statement STMT. If the statement produces an output value and
|
|
its evaluation changes the lattice value of its output, return
|
|
SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
|
|
output value.
|
|
|
|
If STMT is a conditional branch and we can determine its truth
|
|
value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
|
|
value, return SSA_PROP_VARYING. */
|
|
|
|
static enum ssa_prop_result
|
|
ccp_visit_stmt (gimple stmt, edge *taken_edge_p, tree *output_p)
|
|
{
|
|
tree def;
|
|
ssa_op_iter iter;
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "\nVisiting statement:\n");
|
|
print_gimple_stmt (dump_file, stmt, 0, dump_flags);
|
|
}
|
|
|
|
switch (gimple_code (stmt))
|
|
{
|
|
case GIMPLE_ASSIGN:
|
|
/* If the statement is an assignment that produces a single
|
|
output value, evaluate its RHS to see if the lattice value of
|
|
its output has changed. */
|
|
return visit_assignment (stmt, output_p);
|
|
|
|
case GIMPLE_CALL:
|
|
/* A value-returning call also performs an assignment. */
|
|
if (gimple_call_lhs (stmt) != NULL_TREE)
|
|
return visit_assignment (stmt, output_p);
|
|
break;
|
|
|
|
case GIMPLE_COND:
|
|
case GIMPLE_SWITCH:
|
|
/* If STMT is a conditional branch, see if we can determine
|
|
which branch will be taken. */
|
|
/* FIXME. It appears that we should be able to optimize
|
|
computed GOTOs here as well. */
|
|
return visit_cond_stmt (stmt, taken_edge_p);
|
|
|
|
default:
|
|
break;
|
|
}
|
|
|
|
/* Any other kind of statement is not interesting for constant
|
|
propagation and, therefore, not worth simulating. */
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
|
|
|
|
/* Definitions made by statements other than assignments to
|
|
SSA_NAMEs represent unknown modifications to their outputs.
|
|
Mark them VARYING. */
|
|
FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
|
|
{
|
|
prop_value_t v = { VARYING, NULL_TREE };
|
|
set_lattice_value (def, v);
|
|
}
|
|
|
|
return SSA_PROP_VARYING;
|
|
}
|
|
|
|
|
|
/* Main entry point for SSA Conditional Constant Propagation. */
|
|
|
|
static unsigned int
|
|
do_ssa_ccp (void)
|
|
{
|
|
ccp_initialize ();
|
|
ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
|
|
if (ccp_finalize ())
|
|
return (TODO_cleanup_cfg | TODO_update_ssa | TODO_remove_unused_locals);
|
|
else
|
|
return 0;
|
|
}
|
|
|
|
|
|
static bool
|
|
gate_ccp (void)
|
|
{
|
|
return flag_tree_ccp != 0;
|
|
}
|
|
|
|
|
|
struct gimple_opt_pass pass_ccp =
|
|
{
|
|
{
|
|
GIMPLE_PASS,
|
|
"ccp", /* name */
|
|
gate_ccp, /* gate */
|
|
do_ssa_ccp, /* execute */
|
|
NULL, /* sub */
|
|
NULL, /* next */
|
|
0, /* static_pass_number */
|
|
TV_TREE_CCP, /* tv_id */
|
|
PROP_cfg | PROP_ssa, /* properties_required */
|
|
0, /* properties_provided */
|
|
0, /* properties_destroyed */
|
|
0, /* todo_flags_start */
|
|
TODO_dump_func | TODO_verify_ssa
|
|
| TODO_verify_stmts | TODO_ggc_collect/* todo_flags_finish */
|
|
}
|
|
};
|
|
|
|
|
|
|
|
/* Try to optimize out __builtin_stack_restore. Optimize it out
|
|
if there is another __builtin_stack_restore in the same basic
|
|
block and no calls or ASM_EXPRs are in between, or if this block's
|
|
only outgoing edge is to EXIT_BLOCK and there are no calls or
|
|
ASM_EXPRs after this __builtin_stack_restore. */
|
|
|
|
static tree
|
|
optimize_stack_restore (gimple_stmt_iterator i)
|
|
{
|
|
tree callee;
|
|
gimple stmt;
|
|
|
|
basic_block bb = gsi_bb (i);
|
|
gimple call = gsi_stmt (i);
|
|
|
|
if (gimple_code (call) != GIMPLE_CALL
|
|
|| gimple_call_num_args (call) != 1
|
|
|| TREE_CODE (gimple_call_arg (call, 0)) != SSA_NAME
|
|
|| !POINTER_TYPE_P (TREE_TYPE (gimple_call_arg (call, 0))))
|
|
return NULL_TREE;
|
|
|
|
for (gsi_next (&i); !gsi_end_p (i); gsi_next (&i))
|
|
{
|
|
stmt = gsi_stmt (i);
|
|
if (gimple_code (stmt) == GIMPLE_ASM)
|
|
return NULL_TREE;
|
|
if (gimple_code (stmt) != GIMPLE_CALL)
|
|
continue;
|
|
|
|
callee = gimple_call_fndecl (stmt);
|
|
if (!callee
|
|
|| DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
|
|
/* All regular builtins are ok, just obviously not alloca. */
|
|
|| DECL_FUNCTION_CODE (callee) == BUILT_IN_ALLOCA)
|
|
return NULL_TREE;
|
|
|
|
if (DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_RESTORE)
|
|
goto second_stack_restore;
|
|
}
|
|
|
|
if (!gsi_end_p (i))
|
|
return NULL_TREE;
|
|
|
|
/* Allow one successor of the exit block, or zero successors. */
|
|
switch (EDGE_COUNT (bb->succs))
|
|
{
|
|
case 0:
|
|
break;
|
|
case 1:
|
|
if (single_succ_edge (bb)->dest != EXIT_BLOCK_PTR)
|
|
return NULL_TREE;
|
|
break;
|
|
default:
|
|
return NULL_TREE;
|
|
}
|
|
second_stack_restore:
|
|
|
|
/* If there's exactly one use, then zap the call to __builtin_stack_save.
|
|
If there are multiple uses, then the last one should remove the call.
|
|
In any case, whether the call to __builtin_stack_save can be removed
|
|
or not is irrelevant to removing the call to __builtin_stack_restore. */
|
|
if (has_single_use (gimple_call_arg (call, 0)))
|
|
{
|
|
gimple stack_save = SSA_NAME_DEF_STMT (gimple_call_arg (call, 0));
|
|
if (is_gimple_call (stack_save))
|
|
{
|
|
callee = gimple_call_fndecl (stack_save);
|
|
if (callee
|
|
&& DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL
|
|
&& DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_SAVE)
|
|
{
|
|
gimple_stmt_iterator stack_save_gsi;
|
|
tree rhs;
|
|
|
|
stack_save_gsi = gsi_for_stmt (stack_save);
|
|
rhs = build_int_cst (TREE_TYPE (gimple_call_arg (call, 0)), 0);
|
|
update_call_from_tree (&stack_save_gsi, rhs);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* No effect, so the statement will be deleted. */
|
|
return integer_zero_node;
|
|
}
|
|
|
|
/* If va_list type is a simple pointer and nothing special is needed,
|
|
optimize __builtin_va_start (&ap, 0) into ap = __builtin_next_arg (0),
|
|
__builtin_va_end (&ap) out as NOP and __builtin_va_copy into a simple
|
|
pointer assignment. */
|
|
|
|
static tree
|
|
optimize_stdarg_builtin (gimple call)
|
|
{
|
|
tree callee, lhs, rhs, cfun_va_list;
|
|
bool va_list_simple_ptr;
|
|
location_t loc = gimple_location (call);
|
|
|
|
if (gimple_code (call) != GIMPLE_CALL)
|
|
return NULL_TREE;
|
|
|
|
callee = gimple_call_fndecl (call);
|
|
|
|
cfun_va_list = targetm.fn_abi_va_list (callee);
|
|
va_list_simple_ptr = POINTER_TYPE_P (cfun_va_list)
|
|
&& (TREE_TYPE (cfun_va_list) == void_type_node
|
|
|| TREE_TYPE (cfun_va_list) == char_type_node);
|
|
|
|
switch (DECL_FUNCTION_CODE (callee))
|
|
{
|
|
case BUILT_IN_VA_START:
|
|
if (!va_list_simple_ptr
|
|
|| targetm.expand_builtin_va_start != NULL
|
|
|| built_in_decls[BUILT_IN_NEXT_ARG] == NULL)
|
|
return NULL_TREE;
|
|
|
|
if (gimple_call_num_args (call) != 2)
|
|
return NULL_TREE;
|
|
|
|
lhs = gimple_call_arg (call, 0);
|
|
if (!POINTER_TYPE_P (TREE_TYPE (lhs))
|
|
|| TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
|
|
!= TYPE_MAIN_VARIANT (cfun_va_list))
|
|
return NULL_TREE;
|
|
|
|
lhs = build_fold_indirect_ref_loc (loc, lhs);
|
|
rhs = build_call_expr_loc (loc, built_in_decls[BUILT_IN_NEXT_ARG],
|
|
1, integer_zero_node);
|
|
rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
|
|
return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
|
|
|
|
case BUILT_IN_VA_COPY:
|
|
if (!va_list_simple_ptr)
|
|
return NULL_TREE;
|
|
|
|
if (gimple_call_num_args (call) != 2)
|
|
return NULL_TREE;
|
|
|
|
lhs = gimple_call_arg (call, 0);
|
|
if (!POINTER_TYPE_P (TREE_TYPE (lhs))
|
|
|| TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
|
|
!= TYPE_MAIN_VARIANT (cfun_va_list))
|
|
return NULL_TREE;
|
|
|
|
lhs = build_fold_indirect_ref_loc (loc, lhs);
|
|
rhs = gimple_call_arg (call, 1);
|
|
if (TYPE_MAIN_VARIANT (TREE_TYPE (rhs))
|
|
!= TYPE_MAIN_VARIANT (cfun_va_list))
|
|
return NULL_TREE;
|
|
|
|
rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
|
|
return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
|
|
|
|
case BUILT_IN_VA_END:
|
|
/* No effect, so the statement will be deleted. */
|
|
return integer_zero_node;
|
|
|
|
default:
|
|
gcc_unreachable ();
|
|
}
|
|
}
|
|
|
|
/* A simple pass that attempts to fold all builtin functions. This pass
|
|
is run after we've propagated as many constants as we can. */
|
|
|
|
static unsigned int
|
|
execute_fold_all_builtins (void)
|
|
{
|
|
bool cfg_changed = false;
|
|
basic_block bb;
|
|
unsigned int todoflags = 0;
|
|
|
|
FOR_EACH_BB (bb)
|
|
{
|
|
gimple_stmt_iterator i;
|
|
for (i = gsi_start_bb (bb); !gsi_end_p (i); )
|
|
{
|
|
gimple stmt, old_stmt;
|
|
tree callee, result;
|
|
enum built_in_function fcode;
|
|
|
|
stmt = gsi_stmt (i);
|
|
|
|
if (gimple_code (stmt) != GIMPLE_CALL)
|
|
{
|
|
gsi_next (&i);
|
|
continue;
|
|
}
|
|
callee = gimple_call_fndecl (stmt);
|
|
if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
|
|
{
|
|
gsi_next (&i);
|
|
continue;
|
|
}
|
|
fcode = DECL_FUNCTION_CODE (callee);
|
|
|
|
result = gimple_fold_builtin (stmt);
|
|
|
|
if (result)
|
|
gimple_remove_stmt_histograms (cfun, stmt);
|
|
|
|
if (!result)
|
|
switch (DECL_FUNCTION_CODE (callee))
|
|
{
|
|
case BUILT_IN_CONSTANT_P:
|
|
/* Resolve __builtin_constant_p. If it hasn't been
|
|
folded to integer_one_node by now, it's fairly
|
|
certain that the value simply isn't constant. */
|
|
result = integer_zero_node;
|
|
break;
|
|
|
|
case BUILT_IN_STACK_RESTORE:
|
|
result = optimize_stack_restore (i);
|
|
if (result)
|
|
break;
|
|
gsi_next (&i);
|
|
continue;
|
|
|
|
case BUILT_IN_VA_START:
|
|
case BUILT_IN_VA_END:
|
|
case BUILT_IN_VA_COPY:
|
|
/* These shouldn't be folded before pass_stdarg. */
|
|
result = optimize_stdarg_builtin (stmt);
|
|
if (result)
|
|
break;
|
|
/* FALLTHRU */
|
|
|
|
default:
|
|
gsi_next (&i);
|
|
continue;
|
|
}
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "Simplified\n ");
|
|
print_gimple_stmt (dump_file, stmt, 0, dump_flags);
|
|
}
|
|
|
|
old_stmt = stmt;
|
|
if (!update_call_from_tree (&i, result))
|
|
{
|
|
gimplify_and_update_call_from_tree (&i, result);
|
|
todoflags |= TODO_update_address_taken;
|
|
}
|
|
|
|
stmt = gsi_stmt (i);
|
|
update_stmt (stmt);
|
|
|
|
if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt)
|
|
&& gimple_purge_dead_eh_edges (bb))
|
|
cfg_changed = true;
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "to\n ");
|
|
print_gimple_stmt (dump_file, stmt, 0, dump_flags);
|
|
fprintf (dump_file, "\n");
|
|
}
|
|
|
|
/* Retry the same statement if it changed into another
|
|
builtin, there might be new opportunities now. */
|
|
if (gimple_code (stmt) != GIMPLE_CALL)
|
|
{
|
|
gsi_next (&i);
|
|
continue;
|
|
}
|
|
callee = gimple_call_fndecl (stmt);
|
|
if (!callee
|
|
|| DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
|
|
|| DECL_FUNCTION_CODE (callee) == fcode)
|
|
gsi_next (&i);
|
|
}
|
|
}
|
|
|
|
/* Delete unreachable blocks. */
|
|
if (cfg_changed)
|
|
todoflags |= TODO_cleanup_cfg;
|
|
|
|
return todoflags;
|
|
}
|
|
|
|
|
|
struct gimple_opt_pass pass_fold_builtins =
|
|
{
|
|
{
|
|
GIMPLE_PASS,
|
|
"fab", /* name */
|
|
NULL, /* gate */
|
|
execute_fold_all_builtins, /* execute */
|
|
NULL, /* sub */
|
|
NULL, /* next */
|
|
0, /* static_pass_number */
|
|
TV_NONE, /* tv_id */
|
|
PROP_cfg | PROP_ssa, /* properties_required */
|
|
0, /* properties_provided */
|
|
0, /* properties_destroyed */
|
|
0, /* todo_flags_start */
|
|
TODO_dump_func
|
|
| TODO_verify_ssa
|
|
| TODO_update_ssa /* todo_flags_finish */
|
|
}
|
|
};
|