[PATCH] match.pd: Only merge truncation with conversion for -fno-signed-zeros

[PATCH] match.pd: Only merge truncation with conversion for -fno-signed-zeros

[Joe Ramsay]

This optimisation does not honour signed zeros, so should not be
enabled except with -fno-signed-zeros.

OK for master? I do not have commit rights for GCC, so if the patch
is fine would someone be able to commit for me? The bug is present
in all GCC versions from 12.1.0 onwards - is it possible to backport
this?

Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.

Thanks,
Joe

gcc/ChangeLog:

	* match.pd: Fix truncation pattern for -fno-signed-zeroes

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/no_merge_trunc_signed_zero.c: New test.
---
 gcc/match.pd                                  |  2 +-
 .../aarch64/no_merge_trunc_signed_zero.c      | 24 +++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/aarch64/no_merge_trunc_signed_zero.c

diff --git a/gcc/match.pd b/gcc/match.pd
index 9ce313323a3..45c34c810cf 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -4857,7 +4857,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 #if GIMPLE
 (simplify
    (float (fix_trunc @0))
-   (if (!flag_trapping_math
+   (if (!flag_trapping_math && !HONOR_SIGNED_ZEROS(type)
 	&& types_match (type, TREE_TYPE (@0))
 	&& direct_internal_fn_supported_p (IFN_TRUNC, type,
 					  OPTIMIZE_FOR_BOTH))
diff --git a/gcc/testsuite/gcc.target/aarch64/no_merge_trunc_signed_zero.c b/gcc/testsuite/gcc.target/aarch64/no_merge_trunc_signed_zero.c
new file mode 100644
index 00000000000..b2c93e55567
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/no_merge_trunc_signed_zero.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-trapping-math -fsigned-zeros" } */
+
+#include <math.h>
+
+float
+f1 (float x)
+{
+  return (int) rintf(x);
+}
+
+double
+f2 (double x)
+{
+  return (long) rint(x);
+}
+
+/* { dg-final { scan-assembler "frintx\\ts\[0-9\]+, s\[0-9\]+" } } */
+/* { dg-final { scan-assembler "cvtzs\\ts\[0-9\]+, s\[0-9\]+" } } */
+/* { dg-final { scan-assembler "scvtf\\ts\[0-9\]+, s\[0-9\]+" } } */
+/* { dg-final { scan-assembler "frintx\\td\[0-9\]+, d\[0-9\]+" } } */
+/* { dg-final { scan-assembler "cvtzs\\td\[0-9\]+, d\[0-9\]+" } } */
+/* { dg-final { scan-assembler "scvtf\\td\[0-9\]+, d\[0-9\]+" } } */
+
-- 
2.27.0

Re: [PATCH] match.pd: Only merge truncation with conversion for -fno-signed-zeros

[Richard Biener]

On Wed, Mar 13, 2024 at 3:39 PM Joe Ramsay <Joe.Ramsay@arm.com> wrote:
>
> This optimisation does not honour signed zeros, so should not be
> enabled except with -fno-signed-zeros.
>
> OK for master? I do not have commit rights for GCC, so if the patch
> is fine would someone be able to commit for me? The bug is present
> in all GCC versions from 12.1.0 onwards - is it possible to backport
> this?
>
> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
>
> Thanks,
> Joe
>
> gcc/ChangeLog:
>
>         * match.pd: Fix truncation pattern for -fno-signed-zeroes
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/aarch64/no_merge_trunc_signed_zero.c: New test.
> ---
>  gcc/match.pd                                  |  2 +-
>  .../aarch64/no_merge_trunc_signed_zero.c      | 24 +++++++++++++++++++
>  2 files changed, 25 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.target/aarch64/no_merge_trunc_signed_zero.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 9ce313323a3..45c34c810cf 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -4857,7 +4857,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>  #if GIMPLE
>  (simplify
>     (float (fix_trunc @0))
> -   (if (!flag_trapping_math
> +   (if (!flag_trapping_math && !HONOR_SIGNED_ZEROS(type)

put the && to the next line and add a space before (type)

OK with that change.

Richard.

>         && types_match (type, TREE_TYPE (@0))
>         && direct_internal_fn_supported_p (IFN_TRUNC, type,
>                                           OPTIMIZE_FOR_BOTH))
> diff --git a/gcc/testsuite/gcc.target/aarch64/no_merge_trunc_signed_zero.c b/gcc/testsuite/gcc.target/aarch64/no_merge_trunc_signed_zero.c
> new file mode 100644
> index 00000000000..b2c93e55567
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/no_merge_trunc_signed_zero.c
> @@ -0,0 +1,24 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fno-trapping-math -fsigned-zeros" } */
> +
> +#include <math.h>
> +
> +float
> +f1 (float x)
> +{
> +  return (int) rintf(x);
> +}
> +
> +double
> +f2 (double x)
> +{
> +  return (long) rint(x);
> +}
> +
> +/* { dg-final { scan-assembler "frintx\\ts\[0-9\]+, s\[0-9\]+" } } */
> +/* { dg-final { scan-assembler "cvtzs\\ts\[0-9\]+, s\[0-9\]+" } } */
> +/* { dg-final { scan-assembler "scvtf\\ts\[0-9\]+, s\[0-9\]+" } } */
> +/* { dg-final { scan-assembler "frintx\\td\[0-9\]+, d\[0-9\]+" } } */
> +/* { dg-final { scan-assembler "cvtzs\\td\[0-9\]+, d\[0-9\]+" } } */
> +/* { dg-final { scan-assembler "scvtf\\td\[0-9\]+, d\[0-9\]+" } } */
> +
> --
> 2.27.0
>