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sccvn: Fix handling of POINTER_PLUS_EXPR in memset offset [PR93582]

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> > where POINTER_PLUS_EXPR last operand has sizetype type, thus unsigned,
> > and in the testcase gimple_assign_rhs2 (def) is thus 0xf000000000000001ULL
> > which multiplied by 8 doesn't fit into signed HWI.  If it would be treated
> > as signed offset instead, it would fit (-0xfffffffffffffffLL, multiplied
> > by 8 is -0x7ffffffffffffff8LL).  Unfortunately with the poly_int obfuscation
> > I'm not sure how to convert it from unsigned to signed poly_int.
>
> mem_ref_offset provides a boiler-plate for this:
>
> poly_offset_int::from (wi::to_poly_wide (TREE_OPERAND (t, 1)), SIGNED);

Thanks, that seems to work.
The test now works on both big-endian and little-endian.

2020-03-05  Richard Biener  <rguenther@suse.de>
	    Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/93582
	* tree-ssa-sccvn.c (vn_reference_lookup_3): Treat POINTER_PLUS_EXPR
	last operand as signed when looking for memset offset.  Formatting
	fix.

	* gcc.dg/tree-ssa/pr93582-11.c: New test.

Co-authored-by: Richard Biener <rguenther@suse.de>
This commit is contained in:
Jakub Jelinek 2020-03-05 08:00:04 +01:00
parent cb2409c60a
commit fe19699ae2
4 changed files with 37 additions and 4 deletions
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8
gcc/ChangeLog
View File

@ -1,3 +1,11 @@
2020-03-05 Richard Biener <rguenther@suse.de>
Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/93582
* tree-ssa-sccvn.c (vn_reference_lookup_3): Treat POINTER_PLUS_EXPR
last operand as signed when looking for memset offset. Formatting
fix.
2020-03-04 Andrew Pinski <apinski@marvell.com>
PR bootstrap/93962

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2020-03-05 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/93582
* gcc.dg/tree-ssa/pr93582-11.c: New test.
2020-03-04 Martin Sebor <msebor@redhat.com>
PR c++/90938

16
gcc/testsuite/gcc.dg/tree-ssa/pr93582-11.c Normal file
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@ -0,0 +1,16 @@
/* PR tree-optimization/93582 */
/* { dg-do compile { target lp64 } } */
/* { dg-options "-O2 -fdump-tree-fre1" } */
/* { dg-final { scan-tree-dump "return 9223372036854775806;" "fre1" } } */
union U { struct A { unsigned long long a : 1, b : 62, c : 1; } a; unsigned long long i; };
unsigned long long
foo (char *p)
{
__builtin_memset (p - 0xfffffffffffffffULL, 0, 0xffffffffffffffeULL);
__builtin_memset (p + 1, 0, 0xffffffffffffffeULL);
union U *q = (union U *) (void *) (p - 4);
q->a.b = -1;
return q->i;
}

12
gcc/tree-ssa-sccvn.c
View File

@ -2656,7 +2656,8 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
{
poly_int64 soff;
if (TREE_CODE (base) != MEM_REF
|| !(mem_ref_offset (base) << LOG2_BITS_PER_UNIT).to_shwi (&soff))
|| !(mem_ref_offset (base)
<< LOG2_BITS_PER_UNIT).to_shwi (&soff))
return (void *)-1;
offset += soff;
offset2 = 0;
@ -2666,10 +2667,13 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
if (is_gimple_assign (def)
&& gimple_assign_rhs_code (def) == POINTER_PLUS_EXPR
&& gimple_assign_rhs1 (def) == TREE_OPERAND (base, 0)
&& poly_int_tree_p (gimple_assign_rhs2 (def))
&& (wi::to_poly_offset (gimple_assign_rhs2 (def))
<< LOG2_BITS_PER_UNIT).to_shwi (&offset2))
&& poly_int_tree_p (gimple_assign_rhs2 (def)))
{
tree rhs2 = gimple_assign_rhs2 (def);
if (!(poly_offset_int::from (wi::to_poly_wide (rhs2),
SIGNED)
<< LOG2_BITS_PER_UNIT).to_shwi (&offset2))
return (void *)-1;
ref2 = gimple_assign_rhs1 (def);
if (TREE_CODE (ref2) == SSA_NAME)
ref2 = SSA_VAL (ref2);