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tree-optimization/116585 - SSA corruption with split_constant_offset

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split_constant_offset when looking through SSA defs can end up
picking SSA leafs that are subject to abnormal coalescing.  This
can lead to downstream consumers to insert code based on the
result (like from dataref analysis) in places that violate constraints
for abnormal coalescing.  It's best to not expand defs whose operands
are subject to abnormal coalescing - and not either do something when
a subexpression has operands like that already.

	PR tree-optimization/116585
	* tree-data-ref.cc (split_constant_offset_1): When either
	operand is subject to abnormal coalescing do no further
	processing.

	* gcc.dg/torture/pr116585.c: New testcase.
This commit is contained in:
Richard Biener 2024-09-18 09:52:55 +02:00 committed by Richard Biener
parent 45cacfe732
commit 1d0cb3b5fc
2 changed files with 40 additions and 3 deletions
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32
gcc/testsuite/gcc.dg/torture/pr116585.c Normal file
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@ -0,0 +1,32 @@
/* { dg-do compile } */
char *s1, *s2;
extern int* my_alloc (int);
extern int _setjmp ();
extern void bar();
void foo(int s1len, int s2len)
{
int e;
e = _setjmp ();
{
int l, i;
int *md = my_alloc(((sizeof(int)) * (s1len + 1) * (s2len)));
s1len++;
for (; s1len; l)
for (; s2len; l)
for (; s1len; i)
{
int j = 1;
for (; j < s2len; j++)
{
int cost;
if (s1[1] == s2[1])
cost = 0;
else
cost = 1;
md[j * s1len ] = ((cost));
}
}
bar();
}
}

11
gcc/tree-data-ref.cc
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@ -766,6 +766,14 @@ split_constant_offset_1 (tree type, tree op0, enum tree_code code, tree op1,
if (INTEGRAL_TYPE_P (type) && TYPE_OVERFLOW_TRAPS (type))
return false;
if (TREE_CODE (op0) == SSA_NAME
&& SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0))
return false;
if (op1
&& TREE_CODE (op1) == SSA_NAME
&& SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op1))
return false;
switch (code)
{
case INTEGER_CST:
@ -861,9 +869,6 @@ split_constant_offset_1 (tree type, tree op0, enum tree_code code, tree op1,
case SSA_NAME:
{
if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0))
return false;
gimple *def_stmt = SSA_NAME_DEF_STMT (op0);
enum tree_code subcode;