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gimple-low: Fix up handling of volatile automatic vars in assume attribute [PR110754]

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As the following testcases show, the gimple-low outlining of assume
magic functions handled volatile automatic vars (including
parameters/results) like non-volatile ones except it copied volatile
to the new PARM_DECL, which has the undesirable effect that a load
from the volatile var is passed to IFN_ASSUME and so there is a
side-effect there even when side-effects of the assume attribute
shouldn't be evaluated.

The following patch fixes that by passing address of the volatile
variables/parameters/results instead and doing loads or stores from it
or to it where it was originally accessed in the assume attribute
expression.

2024-02-10  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/110754
	* gimple-low.cc (assumption_copy_decl): For TREE_THIS_VOLATILE
	decls create PARM_DECL with pointer to original type, set
	TREE_READONLY and keep TREE_THIS_VOLATILE, TREE_ADDRESSABLE,
	DECL_NOT_GIMPLE_REG_P and DECL_BY_REFERENCE cleared.
	(adjust_assumption_stmt_op): For remapped TREE_THIS_VOLATILE decls
	wrap PARM_DECL into a simple TREE_THIS_NO_TRAP MEM_REF.
	(lower_assumption): For TREE_THIS_VOLATILE vars pass ADDR_EXPR
	of the var as argument.

	* gcc.dg/attr-assume-6.c: New test.
	* g++.dg/cpp23/attr-assume12.C: New test.
This commit is contained in:
Jakub Jelinek 2024-02-10 11:28:00 +01:00
parent 8427290f33
commit 39920447f8
3 changed files with 50 additions and 5 deletions
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27
gcc/gimple-low.cc
View file

@ -374,15 +374,22 @@ assumption_copy_decl (tree decl, copy_body_data *id)
gcc_assert (VAR_P (decl)
|| TREE_CODE (decl) == PARM_DECL
|| TREE_CODE (decl) == RESULT_DECL);
if (TREE_THIS_VOLATILE (decl))
type = build_pointer_type (type);
tree copy = build_decl (DECL_SOURCE_LOCATION (decl),
PARM_DECL, DECL_NAME (decl), type);
if (DECL_PT_UID_SET_P (decl))
SET_DECL_PT_UID (copy, DECL_PT_UID (decl));
TREE_ADDRESSABLE (copy) = TREE_ADDRESSABLE (decl);
TREE_READONLY (copy) = TREE_READONLY (decl);
TREE_THIS_VOLATILE (copy) = TREE_THIS_VOLATILE (decl);
DECL_NOT_GIMPLE_REG_P (copy) = DECL_NOT_GIMPLE_REG_P (decl);
DECL_BY_REFERENCE (copy) = DECL_BY_REFERENCE (decl);
TREE_THIS_VOLATILE (copy) = 0;
if (TREE_THIS_VOLATILE (decl))
TREE_READONLY (copy) = 1;
else
{
TREE_ADDRESSABLE (copy) = TREE_ADDRESSABLE (decl);
TREE_READONLY (copy) = TREE_READONLY (decl);
DECL_NOT_GIMPLE_REG_P (copy) = DECL_NOT_GIMPLE_REG_P (decl);
DECL_BY_REFERENCE (copy) = DECL_BY_REFERENCE (decl);
}
DECL_ARG_TYPE (copy) = type;
((lower_assumption_data *) id)->decls.safe_push (decl);
return copy_decl_for_dup_finish (id, decl, copy);
@ -466,6 +473,11 @@ adjust_assumption_stmt_op (tree *tp, int *, void *datap)
case PARM_DECL:
case RESULT_DECL:
*tp = remap_decl (t, &data->id);
if (TREE_THIS_VOLATILE (t) && *tp != t)
{
*tp = build_simple_mem_ref (*tp);
TREE_THIS_NOTRAP (*tp) = 1;
}
break;
default:
break;
@ -600,6 +612,11 @@ lower_assumption (gimple_stmt_iterator *gsi, struct lower_data *data)
/* Remaining arguments will be the variables/parameters
mentioned in the condition. */
vargs[i - sz] = lad.decls[i - 1];
if (TREE_THIS_VOLATILE (lad.decls[i - 1]))
{
TREE_ADDRESSABLE (lad.decls[i - 1]) = 1;
vargs[i - sz] = build_fold_addr_expr (lad.decls[i - 1]);
}
/* If they have gimple types, we might need to regimplify
them to make the IFN_ASSUME call valid. */
if (is_gimple_reg_type (TREE_TYPE (vargs[i - sz]))

14
gcc/testsuite/g++.dg/cpp23/attr-assume12.C Normal file
View file

@ -0,0 +1,14 @@
// PR middle-end/110754
// { dg-do compile { target c++11 } }
// { dg-options "-O2 -fdump-tree-optimized" }
// { dg-final { scan-tree-dump-times "a ={v} x" 1 "optimized" } }
// { dg-final { scan-tree-dump-not "={v} a" "optimized" } }
// { dg-final { scan-tree-dump-times "return 0;" 1 "optimized" } }
int
foo (int x)
{
volatile int a = x;
[[gnu::assume (x == (a & 0))]];
return x;
}

14
gcc/testsuite/gcc.dg/attr-assume-6.c Normal file
View file

@ -0,0 +1,14 @@
/* PR middle-end/110754 */
/* { dg-do compile } */
/* { dg-options "-std=c23 -O2 -fdump-tree-optimized" } */
/* { dg-final { scan-tree-dump-times "a ={v} x" 1 "optimized" } } */
/* { dg-final { scan-tree-dump-not "={v} a" "optimized" } } */
/* { dg-final { scan-tree-dump-times "return 0;" 1 "optimized" } } */
int
foo (int x)
{
volatile int a = x;
[[gnu::assume (x == (a & 0))]];
return x;
}