* [PATCH] aarch64: Fix undefinedness while testing the J constraint [PR100204]
@ 2024-01-25 19:57 Andrew Pinski
2024-01-26 10:07 ` Alex Coplan
0 siblings, 1 reply; 2+ messages in thread
From: Andrew Pinski @ 2024-01-25 19:57 UTC (permalink / raw)
To: gcc-patches; +Cc: Andrew Pinski
The J constraint can invoke undefined behavior due to it taking the
negative of the ival if ival was HWI_MIN. The fix is simple as casting
to `unsigned HOST_WIDE_INT` before doing the negative of it. This
does that.
Committed as obvious after build/test for aarch64-linux-gnu.
gcc/ChangeLog:
PR target/100204
* config/aarch64/constraints.md (J): Cast to `unsigned HOST_WIDE_INT`
before taking the negative of it.
Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
---
gcc/config/aarch64/constraints.md | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gcc/config/aarch64/constraints.md b/gcc/config/aarch64/constraints.md
index 8566befd727..a2569cea510 100644
--- a/gcc/config/aarch64/constraints.md
+++ b/gcc/config/aarch64/constraints.md
@@ -118,7 +118,7 @@ (define_constraint "Uat"
(define_constraint "J"
"A constant that can be used with a SUB operation (once negated)."
(and (match_code "const_int")
- (match_test "aarch64_uimm12_shift (-ival)")))
+ (match_test "aarch64_uimm12_shift (- (unsigned HOST_WIDE_INT) ival)")))
;; We can't use the mode of a CONST_INT to determine the context in
;; which it is being used, so we must have a separate constraint for
--
2.39.3
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] aarch64: Fix undefinedness while testing the J constraint [PR100204]
2024-01-25 19:57 [PATCH] aarch64: Fix undefinedness while testing the J constraint [PR100204] Andrew Pinski
@ 2024-01-26 10:07 ` Alex Coplan
0 siblings, 0 replies; 2+ messages in thread
From: Alex Coplan @ 2024-01-26 10:07 UTC (permalink / raw)
To: Andrew Pinski; +Cc: gcc-patches
On 25/01/2024 11:57, Andrew Pinski wrote:
> The J constraint can invoke undefined behavior due to it taking the
> negative of the ival if ival was HWI_MIN. The fix is simple as casting
> to `unsigned HOST_WIDE_INT` before doing the negative of it. This
> does that.
Thanks for doing this.
>
> Committed as obvious after build/test for aarch64-linux-gnu.
>
> gcc/ChangeLog:
>
> PR target/100204
> * config/aarch64/constraints.md (J): Cast to `unsigned HOST_WIDE_INT`
> before taking the negative of it.
>
> Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
> ---
> gcc/config/aarch64/constraints.md | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/config/aarch64/constraints.md b/gcc/config/aarch64/constraints.md
> index 8566befd727..a2569cea510 100644
> --- a/gcc/config/aarch64/constraints.md
> +++ b/gcc/config/aarch64/constraints.md
> @@ -118,7 +118,7 @@ (define_constraint "Uat"
> (define_constraint "J"
> "A constant that can be used with a SUB operation (once negated)."
> (and (match_code "const_int")
> - (match_test "aarch64_uimm12_shift (-ival)")))
> + (match_test "aarch64_uimm12_shift (- (unsigned HOST_WIDE_INT) ival)")))
Sorry for the nitpick, but: I don't think we want a space after the unary -
here (at least according to https://gcc.gnu.org/codingconventions.html).
Alex
>
> ;; We can't use the mode of a CONST_INT to determine the context in
> ;; which it is being used, so we must have a separate constraint for
> --
> 2.39.3
>
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2024-01-26 10:07 ` Alex Coplan
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