From: Jakub Jelinek <jakub@redhat.com>
To: Richard Biener <rguenther@suse.de>
Cc: gcc-patches@gcc.gnu.org
Subject: [PATCH] Fix up sqrt(x) < c and sqrt(x) >= c match.pd folding (PR tree-optimization/91734)
Date: Sat, 14 Sep 2019 00:40:00 -0000 [thread overview]
Message-ID: <20190914004014.GE25273@laptop.zalov.cz> (raw)
Hi!
As mentioned in the PR, the sqrt (x) < c optimization into x < c*c
sometimes breaks the boundary case, if c2=c*c is inexact then in some cases
we need to optimize it into x <= c*c rather than x < c*c. The original
bugreport is when c is small and c2 is 0.0, then obviously we need <= 0.0
rather than < 0.0, but the testcase includes another example where it makes
a difference, plus has a >= testcase too.
Bootstrapped/regtested on powerpc64le-linux, ok for trunk?
2019-09-13 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/91734
* generic-match-head.c: Include fold-const-call.h.
* match.pd (sqrt(x) < c, sqrt(x) >= c): Check the boundary value and
in case inexact computation of c*c affects comparison of the boundary,
turn LT_EXPR into LE_EXPR or GE_EXPR into GT_EXPR.
* gcc.dg/pr91734.c: New test.
--- gcc/generic-match-head.c.jj 2019-07-20 21:02:09.296821929 +0200
+++ gcc/generic-match-head.c 2019-09-12 10:52:33.091366624 +0200
@@ -29,6 +29,7 @@ along with GCC; see the file COPYING3.
#include "cgraph.h"
#include "vec-perm-indices.h"
#include "fold-const.h"
+#include "fold-const-call.h"
#include "stor-layout.h"
#include "tree-dfa.h"
#include "builtins.h"
--- gcc/match.pd.jj 2019-09-11 21:50:54.933504293 +0200
+++ gcc/match.pd 2019-09-12 11:12:11.150987786 +0200
@@ -3541,56 +3541,71 @@ (define_operator_list COND_TERNARY
if x is negative or NaN. Due to -funsafe-math-optimizations,
the results for other x follow from natural arithmetic. */
(cmp @0 @1)))
- (if (cmp == GT_EXPR || cmp == GE_EXPR)
+ (if (cmp == LT_EXPR || cmp == LE_EXPR || cmp == GT_EXPR || cmp == GE_EXPR)
(with
{
- REAL_VALUE_TYPE c2;
+ REAL_VALUE_TYPE c2;
+ enum tree_code ncmp = cmp;
real_arithmetic (&c2, MULT_EXPR,
&TREE_REAL_CST (@1), &TREE_REAL_CST (@1));
real_convert (&c2, TYPE_MODE (TREE_TYPE (@0)), &c2);
+ /* See PR91734: if c2 is inexact and sqrt(c2) < c (or sqrt(c2) >= c),
+ then change LT_EXPR into LE_EXPR or GE_EXPR into GT_EXPR. */
+ if ((cmp == LT_EXPR || cmp == GE_EXPR) && !REAL_VALUE_ISINF (c2))
+ {
+ tree c3 = fold_const_call (CFN_SQRT, TREE_TYPE (@0),
+ build_real (TREE_TYPE (@0), c2));
+ if (c3 == NULL_TREE || TREE_CODE (c3) != REAL_CST)
+ ncmp = ERROR_MARK;
+ else if (real_less (&TREE_REAL_CST (c3), &TREE_REAL_CST (@1)))
+ ncmp = cmp == LT_EXPR ? LE_EXPR : GT_EXPR;
+ }
}
- (if (REAL_VALUE_ISINF (c2))
- /* sqrt(x) > y is x == +Inf, when y is very large. */
- (if (HONOR_INFINITIES (@0))
- (eq @0 { build_real (TREE_TYPE (@0), c2); })
- { constant_boolean_node (false, type); })
- /* sqrt(x) > c is the same as x > c*c. */
- (cmp @0 { build_real (TREE_TYPE (@0), c2); }))))
- (if (cmp == LT_EXPR || cmp == LE_EXPR)
- (with
- {
- REAL_VALUE_TYPE c2;
- real_arithmetic (&c2, MULT_EXPR,
- &TREE_REAL_CST (@1), &TREE_REAL_CST (@1));
- real_convert (&c2, TYPE_MODE (TREE_TYPE (@0)), &c2);
- }
- (if (REAL_VALUE_ISINF (c2))
- (switch
- /* sqrt(x) < y is always true, when y is a very large
- value and we don't care about NaNs or Infinities. */
- (if (! HONOR_NANS (@0) && ! HONOR_INFINITIES (@0))
- { constant_boolean_node (true, type); })
- /* sqrt(x) < y is x != +Inf when y is very large and we
- don't care about NaNs. */
- (if (! HONOR_NANS (@0))
- (ne @0 { build_real (TREE_TYPE (@0), c2); }))
- /* sqrt(x) < y is x >= 0 when y is very large and we
- don't care about Infinities. */
- (if (! HONOR_INFINITIES (@0))
- (ge @0 { build_real (TREE_TYPE (@0), dconst0); }))
- /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
- (if (GENERIC)
- (truth_andif
- (ge @0 { build_real (TREE_TYPE (@0), dconst0); })
- (ne @0 { build_real (TREE_TYPE (@0), c2); }))))
- /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
- (if (! HONOR_NANS (@0))
- (cmp @0 { build_real (TREE_TYPE (@0), c2); })
- /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
- (if (GENERIC)
- (truth_andif
- (ge @0 { build_real (TREE_TYPE (@0), dconst0); })
- (cmp @0 { build_real (TREE_TYPE (@0), c2); })))))))))
+ (if (cmp == GT_EXPR || cmp == GE_EXPR)
+ (if (REAL_VALUE_ISINF (c2))
+ /* sqrt(x) > y is x == +Inf, when y is very large. */
+ (if (HONOR_INFINITIES (@0))
+ (eq @0 { build_real (TREE_TYPE (@0), c2); })
+ { constant_boolean_node (false, type); })
+ /* sqrt(x) > c is the same as x > c*c. */
+ (if (ncmp != ERROR_MARK)
+ (if (ncmp == GE_EXPR)
+ (ge @0 { build_real (TREE_TYPE (@0), c2); })
+ (gt @0 { build_real (TREE_TYPE (@0), c2); }))))
+ /* else if (cmp == LT_EXPR || cmp == LE_EXPR) */
+ (if (REAL_VALUE_ISINF (c2))
+ (switch
+ /* sqrt(x) < y is always true, when y is a very large
+ value and we don't care about NaNs or Infinities. */
+ (if (! HONOR_NANS (@0) && ! HONOR_INFINITIES (@0))
+ { constant_boolean_node (true, type); })
+ /* sqrt(x) < y is x != +Inf when y is very large and we
+ don't care about NaNs. */
+ (if (! HONOR_NANS (@0))
+ (ne @0 { build_real (TREE_TYPE (@0), c2); }))
+ /* sqrt(x) < y is x >= 0 when y is very large and we
+ don't care about Infinities. */
+ (if (! HONOR_INFINITIES (@0))
+ (ge @0 { build_real (TREE_TYPE (@0), dconst0); }))
+ /* sqrt(x) < y is x >= 0 && x != +Inf, when y is large. */
+ (if (GENERIC)
+ (truth_andif
+ (ge @0 { build_real (TREE_TYPE (@0), dconst0); })
+ (ne @0 { build_real (TREE_TYPE (@0), c2); }))))
+ /* sqrt(x) < c is the same as x < c*c, if we ignore NaNs. */
+ (if (ncmp != ERROR_MARK && ! HONOR_NANS (@0))
+ (if (ncmp == LT_EXPR)
+ (lt @0 { build_real (TREE_TYPE (@0), c2); })
+ (le @0 { build_real (TREE_TYPE (@0), c2); }))
+ /* sqrt(x) < c is the same as x >= 0 && x < c*c. */
+ (if (ncmp != ERROR_MARK && GENERIC)
+ (if (ncmp == LT_EXPR)
+ (truth_andif
+ (ge @0 { build_real (TREE_TYPE (@0), dconst0); })
+ (lt @0 { build_real (TREE_TYPE (@0), c2); }))
+ (truth_andif
+ (ge @0 { build_real (TREE_TYPE (@0), dconst0); })
+ (le @0 { build_real (TREE_TYPE (@0), c2); })))))))))))
/* Transform sqrt(x) cmp sqrt(y) -> x cmp y. */
(simplify
(cmp (sq @0) (sq @1))
--- gcc/testsuite/gcc.dg/pr91734.c.jj 2019-09-12 10:52:33.094366596 +0200
+++ gcc/testsuite/gcc.dg/pr91734.c 2019-09-12 10:49:10.000000000 +0200
@@ -0,0 +1,34 @@
+/* PR tree-optimization/91734 */
+/* { dg-do run } */
+/* { dg-add-options ieee } */
+/* { dg-additional-options "-ffast-math -O2 -std=gnu99" } */
+
+__attribute__((noipa)) int
+foo (float x)
+{
+ return __builtin_sqrtf (x) < __FLT_MIN__;
+}
+
+__attribute__((noipa)) int
+bar (float x)
+{
+ return __builtin_sqrtf (x) < 0x1.2dd3d0p-65f;
+}
+
+__attribute__((noipa)) int
+baz (float x)
+{
+ return __builtin_sqrtf (x) >= 0x1.2dd3d0p-65f;
+}
+
+int
+main ()
+{
+ if (!foo (0.0f))
+ __builtin_abort ();
+ if (!bar (0x1.63dbc0p-130f))
+ __builtin_abort ();
+ if (baz (0x1.63dbc0p-130f))
+ __builtin_abort ();
+ return 0;
+}
Jakub
next reply other threads:[~2019-09-14 0:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-14 0:40 Jakub Jelinek [this message]
2019-09-16 6:57 ` Richard Biener
2019-09-21 6:14 ` [PATCH] Fix up sqrt(x) < c and sqrt(x) >= c match.pd folding (PR tree-optimization/91734, take 2) Jakub Jelinek
2019-09-30 7:03 ` Patch ping Jakub Jelinek
2019-10-04 20:57 ` [PATCH] Fix up sqrt(x) < c and sqrt(x) >= c match.pd folding (PR tree-optimization/91734, take 2) Jeff Law
2019-09-17 21:16 ` [PATCH] Fix up sqrt(x) < c and sqrt(x) >= c match.pd folding (PR tree-optimization/91734) Joseph Myers
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