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c-family: Cast __atomic_load_*/__atomic_exchange_* result to _BitInt rather then VCE it [PR114469]

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As written in the PR, torture/bitint-64.c test fails with -O2 -flto
and the reason is that on _BitInt arches where the padding bits
are undefined, the padding bits in the _Atomic vars are also undefined,
but when __atomic_load or __atomic_exchange on a _BitInt _Atomic variable
with some padding bits is lowered into __atomic_load_{1,2,4,8,16} or
__atomic_exchange_*, the mode precision unsigned result is VIEW_CONVERT_EXPR
converted to _BitInt and because of the VCE nothing actually sign/zero
extends it as needed for later uses - the var is no longer addressable and
expansion assumes such automatic vars are properly extended.

The following patch fixes that by using NOP_EXPR on it (the
VIEW_CONVERT_EXPR after it will then be optimized away during
gimplification, didn't want to repeat it in the code as else result = build1
(VIEW_CONVERT_EXPR, ...); twice.

2024-03-27  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/114469
	* c-common.cc (resolve_overloaded_builtin): For _BitInt result
	on !extended targets convert result to the _BitInt type before
	using VIEW_CONVERT_EXPR.
This commit is contained in:
Jakub Jelinek 2024-03-27 19:38:06 +01:00
parent f85d3362cd
commit 4b0443361a
1 changed files with 13 additions and 1 deletions
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14
gcc/c-family/c-common.cc
View file

@ -8461,7 +8461,19 @@ resolve_overloaded_builtin (location_t loc, tree function,
if (new_return)
{
/* Cast function result from I{1,2,4,8,16} to the required type. */
result = build1 (VIEW_CONVERT_EXPR, TREE_TYPE (new_return), result);
if (TREE_CODE (TREE_TYPE (new_return)) == BITINT_TYPE)
{
struct bitint_info info;
unsigned prec = TYPE_PRECISION (TREE_TYPE (new_return));
targetm.c.bitint_type_info (prec, &info);
if (!info.extended)
/* For _BitInt which has the padding bits undefined
convert to the _BitInt type rather than VCE to force
zero or sign extension. */
result = build1 (NOP_EXPR, TREE_TYPE (new_return), result);
}
result
= build1 (VIEW_CONVERT_EXPR, TREE_TYPE (new_return), result);
result = build2 (MODIFY_EXPR, TREE_TYPE (new_return), new_return,
result);
TREE_SIDE_EFFECTS (result) = 1;