[gcc r10-7114] rs6000: Check -+0 and NaN for smax/smin generation

[Jiu Fu Guo]

https://gcc.gnu.org/g:37e0df8a9be5a8232f4ccb73cdadb02121ba523f

commit r10-7114-g37e0df8a9be5a8232f4ccb73cdadb02121ba523f
Author: Jiufu Guo <guojiufu@linux.ibm.com>
Date:   Tue Mar 10 13:51:57 2020 +0800

    rs6000: Check -+0 and NaN for smax/smin generation
    
    PR93709 mentioned regressions on maxlocval_4.f90 and minlocval_f.f90 which
    relates to max of '-inf' and 'nan'. This regression occur on P9 because
    P9 new instruction 'xsmaxcdp' is generated.
    And for C code `a < b ? b : a` is also generated as `xsmaxcdp` under -O2
    for P9. While this instruction behavior more like C/C++ semantic (a>b?a:b).
    
    This generates prevents 'xsmaxcdp' to be generated for those cases.
    'xsmincdp' also is handled in patch.
    
    gcc/
    2020-03-10  Jiufu Guo  <guojiufu@linux.ibm.com>
    
            PR target/93709
            * gcc/config/rs6000/rs6000.c (rs6000_emit_p9_fp_minmax): Check
            NAN and SIGNED_ZEROR for smax/smin.
    
    gcc/testsuite
    2020-03-10  Jiufu Guo  <guojiufu@linux.ibm.com>
    
            PR target/93709
            * gcc.target/powerpc/p9-minmax-3.c: New test.

Diff:
---
 gcc/ChangeLog                                  |  6 ++++++
 gcc/config/rs6000/rs6000.c                     |  6 +++++-
 gcc/testsuite/ChangeLog                        |  5 +++++
 gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c | 17 +++++++++++++++++
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c5256616408..5b67b79745f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-10  Jiufu Guo  <guojiufu@linux.ibm.com>
+
+	PR target/93709
+	* gcc/config/rs6000/rs6000.c (rs6000_emit_p9_fp_minmax): Check
+	NAN and SIGNED_ZEROR for smax/smin.
+
 2020-03-10  Will Schmidt  <will_schmidt@vnet.ibm.com>
 
 	PR target/90763
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 848a4ef451e..46b7dec2abd 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -14831,7 +14831,11 @@ rs6000_emit_p9_fp_minmax (rtx dest, rtx op, rtx true_cond, rtx false_cond)
   if (rtx_equal_p (op0, true_cond) && rtx_equal_p (op1, false_cond))
     ;
 
-  else if (rtx_equal_p (op1, true_cond) && rtx_equal_p (op0, false_cond))
+  /* Only when NaNs and signed-zeros are not in effect, smax could be
+     used for `op0 < op1 ? op1 : op0`, and smin could be used for
+     `op0 > op1 ? op1 : op0`.  */
+  else if (rtx_equal_p (op1, true_cond) && rtx_equal_p (op0, false_cond)
+	   && !HONOR_NANS (compare_mode) && !HONOR_SIGNED_ZEROS (compare_mode))
     max_p = !max_p;
 
   else
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index da525a38cf1..c76d891a3e6 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-03-10  Jiufu Guo  <guojiufu@linux.ibm.com>
+
+	PR target/93709
+	* gcc.target/powerpc/p9-minmax-3.c: New test.
+
 2020-03-10  Will Schmidt  <will_schmidt@vnet.ibm.com>
 
 	PR target/90763
diff --git a/gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c b/gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c
new file mode 100644
index 00000000000..141603e05b4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/p9-minmax-3.c
@@ -0,0 +1,17 @@
+/* { dg-do compile { target { powerpc*-*-* } } } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* { dg-options "-mdejagnu-cpu=power9 -O2 -mpower9-minmax" } */
+/* { dg-final { scan-assembler-not "xsmaxcdp"   } } */
+/* { dg-final { scan-assembler-not "xsmincdp"   } } */
+
+double
+dbl_max1 (double a, double b)
+{
+  return a < b ? b : a;
+}
+
+double
+dbl_min1 (double a, double b)
+{
+  return a > b ? b : a;
+}