match.pd: Further fma negation fixes [PR116891]

On Mon, Oct 14, 2024 at 08:53:29AM +0200, Jakub Jelinek wrote:
> >     PR middle-end/116891
> >     * match.pd ((negate (IFN_FNMS@3 @0 @1 @2)) -> (IFN_FMA @0 @1 @2)):
> >     Only enable for !HONOR_SIGN_DEPENDENT_ROUNDING.
>
> Guess it would be nice to have a testcase which FAILs without the patch and
> PASSes with it, but it can be added later.

I've added such a testcase now, and additionally found the fix only fixed
one of the 4 problematic similar cases.

Here is a patch which fixes the others too and adds the testcases.
fma-pr116891.c FAILed without your patch, FAILs with your patch too (but
only due to the bar/baz/qux checks) and PASSes with the patch.

2024-10-15  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/116891
	* match.pd ((negate (fmas@3 @0 @1 @2)) -> (IFN_FNMS @0 @1 @2)):
	Only enable for !HONOR_SIGN_DEPENDENT_ROUNDING.
	((negate (IFN_FMS@3 @0 @1 @2)) -> (IFN_FNMA @0 @1 @2)): Likewise.
	((negate (IFN_FNMA@3 @0 @1 @2)) -> (IFN_FMS @0 @1 @2)): Likewise.

	* gcc.dg/pr116891.c: New test.
	* gcc.target/i386/fma-pr116891.c: New test.

(cherry picked from commit 4366f0c7e296ea0d7279343c9b0a1d597588a1da)

diff --git a/gcc/match.pd b/gcc/match.pd
index d32338c27801444de3d69792d2946071aa49d0d6..06149a740868ba0b824e4b50990a2b07953c41dc 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -7041,7 +7041,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
    (IFN_FNMS @0 @1 @2))
   (simplify
    (negate (fmas@3 @0 @1 @2))
-   (if (single_use (@3))
+   (if (!HONOR_SIGN_DEPENDENT_ROUNDING (type) && single_use (@3))
     (IFN_FNMS @0 @1 @2))))
 
  (simplify
@@ -7055,7 +7055,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (IFN_FNMA @0 @1 @2))
  (simplify
   (negate (IFN_FMS@3 @0 @1 @2))
-   (if (single_use (@3))
+   (if (!HONOR_SIGN_DEPENDENT_ROUNDING (type) && single_use (@3))
     (IFN_FNMA @0 @1 @2)))
 
  (simplify
@@ -7069,7 +7069,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (IFN_FMS @0 @1 @2))
  (simplify
   (negate (IFN_FNMA@3 @0 @1 @2))
-  (if (single_use (@3))
+  (if (!HONOR_SIGN_DEPENDENT_ROUNDING (type) && single_use (@3))
    (IFN_FMS @0 @1 @2)))
 
  (simplify

diff --git a/gcc/testsuite/gcc.dg/pr116891.c b/gcc/testsuite/gcc.dg/pr116891.c
new file mode 100644 (file)
index 0000000..446e5ec
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr116891.c
@@ -0,0 +1,47 @@
+/* PR middle-end/116891 */
+/* { dg-do run } */
+/* { dg-require-effective-target fenv } */
+/* { dg-require-effective-target hard_float } */
+/* { dg-require-effective-target c99_runtime } */
+/* { dg-options "-O2 -frounding-math" } */
+
+#include <fenv.h>
+
+__attribute__((noipa)) double
+foo (double x, double y, double z)
+{
+  return -__builtin_fma (-x, y, -z);
+}
+
+__attribute__((noipa)) double
+bar (double x, double y, double z)
+{
+  return -__builtin_fma (-x, y, z);
+}
+
+__attribute__((noipa)) double
+baz (double x, double y, double z)
+{
+  return -__builtin_fma (x, y, -z);
+}
+
+__attribute__((noipa)) double
+qux (double x, double y, double z)
+{
+  return -__builtin_fma (x, y, z);
+}
+
+int
+main ()
+{
+#if defined (FE_DOWNWARD) && __DBL_MANT_DIG__ == 53 && __DBL_MAX_EXP__ == 1024
+  fesetround (FE_DOWNWARD);
+  double a = foo (-0x1.p256, 0x1.p256, 0x1.p-256);
+  if (a != -__builtin_nextafter (0x1p256 * 0x1p256, 0.))
+    __builtin_abort ();
+  if (a != bar (-0x1.p256, 0x1.p256, -0x1.p-256)
+      || a != baz (0x1.p256, 0x1.p256, 0x1.p-256)
+      || a != qux (0x1.p256, 0x1.p256, -0x1.p-256))
+    __builtin_abort ();
+#endif
+}

diff --git a/gcc/testsuite/gcc.target/i386/fma-pr116891.c b/gcc/testsuite/gcc.target/i386/fma-pr116891.c
new file mode 100644 (file)
index 0000000..34689f4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/fma-pr116891.c
@@ -0,0 +1,19 @@
+/* PR middle-end/116891 */
+/* { dg-do run } */
+/* { dg-require-effective-target fenv } */
+/* { dg-require-effective-target hard_float } */
+/* { dg-require-effective-target c99_runtime } */
+/* { dg-require-effective-target fma } */
+/* { dg-options "-O2 -mfma -frounding-math" } */
+
+#include <fenv.h>
+#include "fma-check.h"
+
+#define main() do_main ()
+#include "../../gcc.dg/pr116891.c"
+
+static void
+fma_test (void)
+{
+  do_main ();
+}