[gcc(refs/vendors/ARM/heads/arm-struct-reorg-wip)] rtl combine should consider NaNs when generate fp min/max [PR94708]

[Tamar Christina]

https://gcc.gnu.org/g:cbd2a10dd9edadb262934aed64c0959339da68d1

commit cbd2a10dd9edadb262934aed64c0959339da68d1
Author: Haijian Zhang <z.zhanghaijian@huawei.com>
Date:   Fri Apr 24 08:56:25 2020 +0800

    rtl combine should consider NaNs when generate fp min/max [PR94708]
    
        As discussed on PR94708, it's unsafe for rtl combine to generate fp
        min/max under -funsafe-math-optimizations, considering NaNs. In
        addition to flag_unsafe_math_optimizations check, we also need to
        do extra mode feature testing here: && !HONOR_NANS (mode)
        && !HONOR_SIGNED_ZEROS (mode)
    
        2020-04-24  Haijian Zhang <z.zhanghaijian@huawei.com>
    
        gcc/
            PR rtl-optimization/94708
            * combine.c (simplify_if_then_else): Add check for
            !HONOR_NANS (mode) && !HONOR_SIGNED_ZEROS (mode).
        gcc/testsuite/
            PR fortran/94708
            * gfortran.dg/pr94708.f90: New test.

Diff:
---
 gcc/ChangeLog                         |  6 ++++++
 gcc/combine.c                         |  5 ++++-
 gcc/testsuite/ChangeLog               |  5 +++++
 gcc/testsuite/gfortran.dg/pr94708.f90 | 13 +++++++++++++
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index cf97cfed626..6032e681d7f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-24  Haijian Zhang <z.zhanghaijian@huawei.com>
+
+	PR rtl-optimization/94708
+	* combine.c (simplify_if_then_else): Add check for
+	!HONOR_NANS (mode) && !HONOR_SIGNED_ZEROS (mode).
+
 2020-04-23  Martin Sebor  <msebor@redhat.com>
 
 	PR driver/90983
diff --git a/gcc/combine.c b/gcc/combine.c
index cff76cd3303..4c324f38660 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -6643,7 +6643,10 @@ simplify_if_then_else (rtx x)
 
   /* Look for MIN or MAX.  */
 
-  if ((! FLOAT_MODE_P (mode) || flag_unsafe_math_optimizations)
+  if ((! FLOAT_MODE_P (mode)
+       || (flag_unsafe_math_optimizations
+	   && !HONOR_NANS (mode)
+	   && !HONOR_SIGNED_ZEROS (mode)))
       && comparison_p
       && rtx_equal_p (XEXP (cond, 0), true_rtx)
       && rtx_equal_p (XEXP (cond, 1), false_rtx)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a955cd5f4f8..4b1e9e11e7c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-04-24  Haijian Zhang <z.zhanghaijian@huawei.com>
+
+	PR rtl-optimization/94708
+	* gfortran.dg/pr94708.f90: New test.
+
 2020-04-23  David Edelsohn  <dje.gcc@gmail.com>
 
 	* gcc.dg/torture/pr90020.c: Skip on AIX.
diff --git a/gcc/testsuite/gfortran.dg/pr94708.f90 b/gcc/testsuite/gfortran.dg/pr94708.f90
new file mode 100644
index 00000000000..9b5f1389f09
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr94708.f90
@@ -0,0 +1,13 @@
+! { dg-do compile { target aarch64*-*-* } }
+! { dg-options "-O2 -funsafe-math-optimizations -fdump-rtl-combine" }
+
+subroutine f(vara,varb,varc,res)
+      REAL, INTENT(IN) :: vara,varb,varc
+      REAL, INTENT(out) :: res
+
+      res = vara
+      if (res .lt. varb)  res = varb
+      if (res .gt. varc)  res = varc
+end subroutine
+
+! { dg-final { scan-rtl-dump-not "smin" "combine" } }