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tree-ssa-alias.c (stmt_may_clobber_ref_p): Improve handling of accesses with non-invariant address. 

2014-06-04  Richard Biener  <rguenther@suse.de>

	* tree-ssa-alias.c (stmt_may_clobber_ref_p): Improve handling
	of accesses with non-invariant address.

	* gcc.dg/tree-ssa/ssa-dse-16.c: New testcase.

From-SVN: r211223
This commit is contained in:
Richard Biener 2014-06-04 11:55:29 +00:00 committed by Richard Biener
parent 8be2dc8cb2
commit b1259d34e9
4 changed files with 76 additions and 7 deletions
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5
gcc/ChangeLog
View File

@ -1,3 +1,8 @@
2014-06-04 Richard Biener <rguenther@suse.de>
* tree-ssa-alias.c (stmt_may_clobber_ref_p): Improve handling
of accesses with non-invariant address.
2014-06-04 Martin Liska <mliska@suse.cz>
* cgraph.h (cgraph_make_wrapper): New function introduced.

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2014-06-04 Richard Biener <rguenther@suse.de>
* gcc.dg/tree-ssa/ssa-dse-16.c: New testcase.
2014-06-04 Igor Zamyatin <igor.zamyatin@intel.com>
PR c/58942

18
gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-16.c Normal file
View File

@ -0,0 +1,18 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-dse1-details" } */
struct X { struct A { int a[2]; } b[10]; };
void foo (struct X *x, int i)
{
struct A a;
/* Confuse SRA here with using a variable index, otherwise it will mess
with the IL too much. */
a.a[i] = 3;
a.a[1] = 0;
/* The following store is dead. */
x->b[i].a[0] = 1;
x->b[i] = a;
}
/* { dg-final { scan-tree-dump "Deleted dead store" "dse1" } } */
/* { dg-final { cleanup-tree-dump "dse1" } } */

56
gcc/tree-ssa-alias.c
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@ -2174,11 +2174,7 @@ stmt_may_clobber_ref_p (gimple stmt, tree ref)
static bool
stmt_kills_ref_p_1 (gimple stmt, ao_ref *ref)
{
/* For a must-alias check we need to be able to constrain
the access properly.
FIXME: except for BUILTIN_FREE. */
if (!ao_ref_base (ref)
|| ref->max_size == -1)
if (!ao_ref_base (ref))
return false;
if (gimple_has_lhs (stmt)
@ -2191,9 +2187,51 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref *ref)
might throw as well. */
&& !stmt_can_throw_internal (stmt))
{
tree base, lhs = gimple_get_lhs (stmt);
tree lhs = gimple_get_lhs (stmt);
/* If LHS is literally a base of the access we are done. */
if (ref->ref)
{
tree base = ref->ref;
if (handled_component_p (base))
{
tree saved_lhs0 = NULL_TREE;
if (handled_component_p (lhs))
{
saved_lhs0 = TREE_OPERAND (lhs, 0);
TREE_OPERAND (lhs, 0) = integer_zero_node;
}
do
{
/* Just compare the outermost handled component, if
they are equal we have found a possible common
base. */
tree saved_base0 = TREE_OPERAND (base, 0);
TREE_OPERAND (base, 0) = integer_zero_node;
bool res = operand_equal_p (lhs, base, 0);
TREE_OPERAND (base, 0) = saved_base0;
if (res)
break;
/* Otherwise drop handled components of the access. */
base = saved_base0;
}
while (handled_component_p (base));
if (saved_lhs0)
TREE_OPERAND (lhs, 0) = saved_lhs0;
}
/* Finally check if lhs is equal or equal to the base candidate
of the access. */
if (operand_equal_p (lhs, base, 0))
return true;
}
/* Now look for non-literal equal bases with the restriction of
handling constant offset and size. */
/* For a must-alias check we need to be able to constrain
the access properly. */
if (ref->max_size == -1)
return false;
HOST_WIDE_INT size, offset, max_size, ref_offset = ref->offset;
base = get_ref_base_and_extent (lhs, &offset, &size, &max_size);
tree base = get_ref_base_and_extent (lhs, &offset, &size, &max_size);
/* We can get MEM[symbol: sZ, index: D.8862_1] here,
so base == ref->base does not always hold. */
if (base != ref->base)
@ -2261,6 +2299,10 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref *ref)
case BUILT_IN_MEMMOVE_CHK:
case BUILT_IN_MEMSET_CHK:
{
/* For a must-alias check we need to be able to constrain
the access properly. */
if (ref->max_size == -1)
return false;
tree dest = gimple_call_arg (stmt, 0);
tree len = gimple_call_arg (stmt, 2);
if (!tree_fits_shwi_p (len))