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rtl combine should consider NaNs when generate fp min/max [PR94708]

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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.
This commit is contained in:
Haijian Zhang 2020-04-24 08:56:25 +08:00 committed by Richard Biener
parent 6f6c799208
commit cbd2a10dd9
4 changed files with 28 additions and 1 deletions
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6
gcc/ChangeLog
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@ -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

5
gcc/combine.c
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@ -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)

5
gcc/testsuite/ChangeLog
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@ -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.

13
gcc/testsuite/gfortran.dg/pr94708.f90 Normal file
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@ -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" } }