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This patch skips constant folding for fmin/max when either argument is sNaN. According to C standard, fmin(sNaN, sNaN）= qNaN, fmin(sNaN, NaN) = qNaN.

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gcc/
	PR target/105414
	* match.pd (minmax): Skip constant folding for fmin/fmax when both
	arguments are sNaN or one is sNaN and another is NaN.

gcc/testsuite/
	PR target/105414
	* gcc.dg/pr105414.c: New.
This commit is contained in:
Haochen Gui 2022-05-09 17:34:23 +08:00
parent e877898911
commit 344e425340
2 changed files with 42 additions and 5 deletions
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17
gcc/match.pd
View file

@ -3089,10 +3089,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
/* Simplifications of MIN_EXPR, MAX_EXPR, fmin() and fmax(). */
(for minmax (min max FMIN_ALL FMAX_ALL)
(for minmax (min max)
(simplify
(minmax @0 @0)
@0))
/* For fmin() and fmax(), skip folding when both are sNaN. */
(for minmax (FMIN_ALL FMAX_ALL)
(simplify
(minmax @0 @0)
(if (!tree_expr_maybe_signaling_nan_p (@0))
@0)))
/* min(max(x,y),y) -> y. */
(simplify
(min:c (max:c @0 @1) @1)
@ -3192,12 +3198,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(minmax @1 (convert @2)))))
(for minmax (FMIN_ALL FMAX_ALL)
/* If either argument is NaN, return the other one. Avoid the
transformation if we get (and honor) a signalling NaN. */
/* If either argument is NaN and other one is not sNaN, return the other
one. Avoid the transformation if we get (and honor) a signalling NaN. */
(simplify
(minmax:c @0 REAL_CST@1)
(if (real_isnan (TREE_REAL_CST_PTR (@1))
&& (!HONOR_SNANS (@1) || !TREE_REAL_CST (@1).signalling))
(if (real_isnan (TREE_REAL_CST_PTR (@1))
&& (!HONOR_SNANS (@1) || !TREE_REAL_CST (@1).signalling)
&& !tree_expr_maybe_signaling_nan_p (@0))
@0)))
/* Convert fmin/fmax to MIN_EXPR/MAX_EXPR. C99 requires these
functions to return the numeric arg if the other one is NaN.

30
gcc/testsuite/gcc.dg/pr105414.c Normal file
View file

@ -0,0 +1,30 @@
/* { dg-do run { target { *-*-linux* *-*-gnu* } } } */
/* { dg-options "-O1 -fsignaling-nans -lm" } */
/* { dg-add-options ieee } */
/* { dg-require-effective-target issignaling } */
#define _GNU_SOURCE
#include <stdio.h>
#include <math.h>
int main()
{
double a = __builtin_nans ("");
if (issignaling (fmin (a, a)))
__builtin_abort ();
if (issignaling (fmax (a, a)))
__builtin_abort ();
double b = __builtin_nan ("");
if (issignaling (fmin (a, b)))
__builtin_abort ();
if (issignaling (fmax (a, b)))
__builtin_abort ();
return 0;
}