diff mbox series

x86_64: Fix asm constraints in feraiseexcept (bug 30305)

Message ID 87bkk50y5n.fsf@oldenburg.str.redhat.com
State New
Headers show
Series x86_64: Fix asm constraints in feraiseexcept (bug 30305) | expand

Commit Message

Florian Weimer April 3, 2023, 3:43 p.m. UTC 
The divss instruction clobbers its first argument, and the constraints
need to reflect that.  Fortunately, with GCC 12, generated code does
not actually change, so there is no externally visible bug.

Tested on x86_64-linux-gnu.

Suggested-by: Jakub Jelinek <jakub@redhat.com>

---
 sysdeps/x86_64/fpu/fraiseexcpt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


base-commit: ac2a14343e81098c196cef5d67b52e440c05c230

Comments

Noah Goldstein April 3, 2023, 3:55 p.m. UTC | #1 
On Mon, Apr 3, 2023 at 10:43 AM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> The divss instruction clobbers its first argument, and the constraints
> need to reflect that.  Fortunately, with GCC 12, generated code does
> not actually change, so there is no externally visible bug.
>
> Tested on x86_64-linux-gnu.
>
> Suggested-by: Jakub Jelinek <jakub@redhat.com>
>
> ---
>  sysdeps/x86_64/fpu/fraiseexcpt.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/sysdeps/x86_64/fpu/fraiseexcpt.c b/sysdeps/x86_64/fpu/fraiseexcpt.c
> index 924eed96a9..e7430a4158 100644
> --- a/sysdeps/x86_64/fpu/fraiseexcpt.c
> +++ b/sysdeps/x86_64/fpu/fraiseexcpt.c
> @@ -33,7 +33,7 @@ __feraiseexcept (int excepts)
>        /* One example of an invalid operation is 0.0 / 0.0.  */
>        float f = 0.0;
>
> -      __asm__ __volatile__ ("divss %0, %0 " : : "x" (f));
> +      __asm__ __volatile__ ("divss %0, %0 " : "+x" (f));
>        (void) &f;
>      }
>
> @@ -43,7 +43,7 @@ __feraiseexcept (int excepts)
>        float f = 1.0;
>        float g = 0.0;
>
> -      __asm__ __volatile__ ("divss %1, %0" : : "x" (f), "x" (g));
> +      __asm__ __volatile__ ("divss %1, %0" : "+x" (f) : "x" (g));
>        (void) &f;
>      }
>
>
> base-commit: ac2a14343e81098c196cef5d67b52e440c05c230
>

LGTM.

Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com
diff mbox series

Patch

diff --git a/sysdeps/x86_64/fpu/fraiseexcpt.c b/sysdeps/x86_64/fpu/fraiseexcpt.c
index 924eed96a9..e7430a4158 100644
--- a/sysdeps/x86_64/fpu/fraiseexcpt.c
+++ b/sysdeps/x86_64/fpu/fraiseexcpt.c
@@ -33,7 +33,7 @@  __feraiseexcept (int excepts)
       /* One example of an invalid operation is 0.0 / 0.0.  */
       float f = 0.0;
 
-      __asm__ __volatile__ ("divss %0, %0 " : : "x" (f));
+      __asm__ __volatile__ ("divss %0, %0 " : "+x" (f));
       (void) &f;
     }
 
@@ -43,7 +43,7 @@  __feraiseexcept (int excepts)
       float f = 1.0;
       float g = 0.0;
 
-      __asm__ __volatile__ ("divss %1, %0" : : "x" (f), "x" (g));
+      __asm__ __volatile__ ("divss %1, %0" : "+x" (f) : "x" (g));
       (void) &f;
     }