From: HAO CHEN GUI <guihaoc@linux.ibm.com>
To: gcc-patches <gcc-patches@gcc.gnu.org>
Cc: Segher Boessenkool <segher@kernel.crashing.org>,
David <dje.gcc@gmail.com>, "Kewen.Lin" <linkw@linux.ibm.com>,
Peter Bergner <bergner@linux.ibm.com>
Subject: [PATCH] Skip constant folding for fmin/max when either argument is sNaN [PR105414]
Date: Thu, 5 May 2022 16:06:52 +0800 [thread overview]
Message-ID: <4df302c6-5bc7-f6fb-916a-6dd9c0460268@linux.ibm.com> (raw)
Hi,
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
So signaling NaN should be tested and skipped for fmin/max in match.pd.
Bootstrapped and tested on ppc64 Linux BE and LE with no regressions.
Is this okay for trunk? Any recommendations? Thanks a lot.
ChangeLog
2022-05-05 Haochen Gui <guihaoc@linux.ibm.com>
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.
patch.diff
diff --git a/gcc/match.pd b/gcc/match.pd
index cad61848daa..f256bcbb483 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3093,7 +3093,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(for minmax (min max FMIN_ALL FMAX_ALL)
(simplify
(minmax @0 @0)
- @0))
+ /* if both are sNaN, it should return qNaN. */
+ (if (!tree_expr_maybe_signaling_nan_p (@0))
+ @0)))
/* min(max(x,y),y) -> y. */
(simplify
(min:c (max:c @0 @1) @1)
@@ -3193,12 +3195,13 @@ 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.
diff --git a/gcc/testsuite/gcc.dg/pr105414.c b/gcc/testsuite/gcc.dg/pr105414.c
new file mode 100644
index 00000000000..78772700acf
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr105414.c
@@ -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;
+}
next reply other threads:[~2022-05-05 8:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-05 8:06 HAO CHEN GUI [this message]
2022-05-05 8:09 ` Richard Biener
2022-05-05 8:30 ` Kewen.Lin
2022-05-05 8:35 ` Richard Biener
2022-05-05 17:11 ` Joseph Myers
2022-05-06 6:17 ` Richard Biener
2022-05-05 9:30 ` HAO CHEN GUI
2022-05-05 13:23 ` Segher Boessenkool
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