[gcc(refs/vendors/ARM/heads/arm-struct-reorg-wip)] i386: Avoid reversing a non-trapping comparison to a trapping one [PR95169]

[Tamar Christina]

https://gcc.gnu.org/g:ddfb80adbd91a0e45cc6e04a8b0dbe3ca15ba45f

commit ddfb80adbd91a0e45cc6e04a8b0dbe3ca15ba45f
Author: Uros Bizjak <ubizjak@gmail.com>
Date:   Thu May 21 19:36:32 2020 +0200

    i386: Avoid reversing a non-trapping comparison to a trapping one [PR95169]
    
    2020-05-21  Uroš Bizjak  <ubizjak@gmail.com>
    
    gcc/ChangeLog:
            PR target/95169
            * config/i386/i386-expand.c (ix86_expand_int_movcc):
             Avoid reversing a non-trapping comparison to a trapping one.
    
    gcc/testsuite/ChangeLog:
            PR target/95169
            * gcc.target/i386/pr95169.c: New test.

Diff:
---
 gcc/ChangeLog                           |  6 ++++++
 gcc/config/i386/i386-expand.c           | 27 +++++++++++++++++----------
 gcc/testsuite/ChangeLog                 |  5 +++++
 gcc/testsuite/gcc.target/i386/pr95169.c | 28 ++++++++++++++++++++++++++++
 4 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index be6787b08e9..076b8f4c906 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-05-21  Uroš Bizjak  <ubizjak@gmail.com>
+
+	PR target/95169
+	* config/i386/i386-expand.c (ix86_expand_int_movcc):
+	 Avoid reversing a non-trapping comparison to a trapping one.
+
 2020-05-21  Martin Liska  <mliska@suse.cz>
 
 	* common/config/aarch64/aarch64-common.c (aarch64_handle_option):
diff --git a/gcc/config/i386/i386-expand.c b/gcc/config/i386/i386-expand.c
index 48f00c5fcfc..6c759b01edf 100644
--- a/gcc/config/i386/i386-expand.c
+++ b/gcc/config/i386/i386-expand.c
@@ -3059,11 +3059,14 @@ ix86_expand_int_movcc (rtx operands[])
 	    {
 	      gcc_assert (!DECIMAL_FLOAT_MODE_P (cmp_mode));
 
-	      /* We may be reversing unordered compare to normal compare, that
-		 is not valid in general (we may convert non-trapping condition
-		 to trapping one), however on i386 we currently emit all
-		 comparisons unordered.  */
-	      new_code = reverse_condition_maybe_unordered (code);
+	      /* We may be reversing a non-trapping
+		 comparison to a trapping comparison.  */
+		  if (HONOR_NANS (cmp_mode) && flag_trapping_math
+		      && code != EQ && code != NE
+		      && code != ORDERED && code != UNORDERED)
+		    new_code = UNKNOWN;
+		  else
+		    new_code = reverse_condition_maybe_unordered (code);
 	    }
 	  else
 	    new_code = ix86_reverse_condition (code, cmp_mode);
@@ -3215,11 +3218,15 @@ ix86_expand_int_movcc (rtx operands[])
 		{
 		  gcc_assert (!DECIMAL_FLOAT_MODE_P (cmp_mode));
 
-		  /* We may be reversing unordered compare to normal compare,
-		     that is not valid in general (we may convert non-trapping
-		     condition to trapping one), however on i386 we currently
-		     emit all comparisons unordered.  */
-		  new_code = reverse_condition_maybe_unordered (code);
+		  /* We may be reversing a non-trapping
+		     comparison to a trapping comparison.  */
+		  if (HONOR_NANS (cmp_mode) && flag_trapping_math
+		      && code != EQ && code != NE
+		      && code != ORDERED && code != UNORDERED)
+		    new_code = UNKNOWN;
+		  else
+		    new_code = reverse_condition_maybe_unordered (code);
+
 		}
 	      else
 		{
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 92a989fab08..74b4d088591 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-21  Uroš Bizjak  <ubizjak@gmail.com>
+
+	PR target/95169
+	* gcc.target/i386/pr95169.c: New test.
+
 2020-05-21  Martin Liska  <mliska@suse.cz>
 
 	* gcc.target/aarch64/target_attr_20.c: New test.
diff --git a/gcc/testsuite/gcc.target/i386/pr95169.c b/gcc/testsuite/gcc.target/i386/pr95169.c
new file mode 100644
index 00000000000..91411744228
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95169.c
@@ -0,0 +1,28 @@
+/* PR target/95169 */
+/* { dg-do run { target ia32 } } */
+/* { dg-options "-O0 -march=i386 -mtune=generic" } */
+/* { dg-require-effective-target fenv_exceptions } */
+
+#include <fenv.h>
+
+void
+f (double y)
+{
+  if (__builtin_expect (y == 0.0, 0))
+    __builtin_abort ();
+}
+
+int
+main (void)
+{
+  double y = __builtin_nan ("");
+
+  feclearexcept (FE_INVALID);
+
+  f (y);
+
+  if (fetestexcept (FE_INVALID))
+    __builtin_abort ();
+
+  return 0;
+}