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tree-ssa-dse.c (dse_optimize_stmt): Correctly handle PHI nodes which represent a use and definition of the same...

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* tree-ssa-dse.c (dse_optimize_stmt): Correctly handle PHI nodes which
	represent a use and definition of the same SSA_NAME.

	* gcc.dg/tree-ssa/ssa-dse-8.c: New test.

From-SVN: r108630
This commit is contained in:
Jeff Law 2005-12-16 00:03:12 -07:00 committed by Jeff Law
parent 9a8ce21f3b
commit 7d48c9e2cc
4 changed files with 44 additions and 0 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2005-12-16 Jeff Law <law@redhat.com>
* tree-ssa-dse.c (dse_optimize_stmt): Correctly handle PHI nodes which
represent a use and definition of the same SSA_NAME.
2005-12-16 Jon Grimm <jgrimm2@us.ibm.com>
Janis Johnson <janis187@us.ibm.com>
Ben Elliston <bje@au.ibm.com>

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2005-12-16 Jeff Law <law@redhat.com>
* gcc.dg/tree-ssa/ssa-dse-8.c: New test.
2005-12-16 Andrew Pinski <pinskia@physics.uc.edu>
* objc.dg/gnu-encoding/struct-layout-encoding-1_generate.c (base_types):

26
gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-8.c Normal file
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@ -0,0 +1,26 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fno-tree-dce -fno-tree-ccp -fno-tree-copy-prop -fno-tree-dominator-opts" } */
/* This caused the compiler to enter an infinite loop if copies are not
fully propagated. The options are to disable copy propagation and
thus expose the bug. */
int foo (void);
struct A {
struct B {
struct B *n;
} *p;
};
static inline void baz (struct A *a)
{
a->p = a->p->n;
}
void bar (struct A a)
{
while (foo ())
baz (&a);
while (foo ());
}

9
gcc/tree-ssa-dse.c
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@ -309,6 +309,15 @@ dse_optimize_stmt (struct dom_walk_data *walk_data,
&& TREE_CODE (use_stmt) == PHI_NODE
&& bitmap_bit_p (dse_gd->stores, get_stmt_uid (use_stmt)))
{
/* A PHI node can both define and use the same SSA_NAME if
the PHI is at the top of a loop and the PHI_RESULT is
a loop invariant and copies have not been fully propagated.
The safe thing to do is exit assuming no optimization is
possible. */
if (SSA_NAME_DEF_STMT (PHI_RESULT (use_stmt)) == use_stmt)
return;
/* Skip past this PHI and loop again in case we had a PHI
chain. */
if (single_imm_use (PHI_RESULT (use_stmt), &use_p, &use_stmt))