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store-merging: Avoid ICEs on roughly ~0ULL/8 sized stores [PR105094] 

On the following testcase on 64-bit targets, store-merging sees
a MEM_REF store from {} ctor with "negative" bitsize where bitoff + bitsize
wraps around to very small end offset.  This later confuses the code
so that it allocates just a few bytes of memory but fills in huge amounts of
it.  Later on there is a param_store_merging_max_size size check but due to
the wrap-around we pass that.

The following patch punts on such large bitsizes.

2022-03-30  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/105094
	* gimple-ssa-store-merging.cc (mem_valid_for_store_merging): Punt if
	bitsize <= 0 rather than just == 0.

	* gcc.dg/pr105094.c: New test.
This commit is contained in:
Jakub Jelinek 2022-03-30 10:21:16 +02:00
parent 410f39f56c
commit 387e818cda
2 changed files with 14 additions and 1 deletions
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2
gcc/gimple-ssa-store-merging.cc
View File

@ -4940,7 +4940,7 @@ mem_valid_for_store_merging (tree mem, poly_uint64 *pbitsize,
tree base_addr = get_inner_reference (mem, &bitsize, &bitpos, &offset, &mode,
&unsignedp, &reversep, &volatilep);
*pbitsize = bitsize;
if (known_eq (bitsize, 0))
if (known_le (bitsize, 0))
return NULL_TREE;
if (TREE_CODE (mem) == COMPONENT_REF

13
gcc/testsuite/gcc.dg/pr105094.c Normal file
View File

@ -0,0 +1,13 @@
/* PR tree-optimization/105094 */
/* { dg-do compile } */
/* { dg-options "-O2" } */
struct S { short a; char b[~(__SIZE_TYPE__)0 / __CHAR_BIT__ - 1]; };
void bar (struct S *);
void
foo (void)
{
struct S s = { 5 };
bar (&s);
}