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re PR middle-end/19775 (sqrt(pow(x,y)) != pow(x,y*0.5) (with -ffast-math))

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2005-02-07  Richard Guenther  <rguenth@gcc.gnu.org>

	PR middle-end/19775
	* builtins.c (fold_builtin_sqrt): Transform
	sqrt(pow(x,y)) to pow(fabs(x),y*0.5), not
	pow(x,y*0.5).

	* gcc.dg/torture/builtin-power-1.c: Disable test for
	invalid transformation.
	* gcc.dg/builtins-10.c: Likewise.  Disable one test we
	no longer optimize.
	* gcc.dg/builtins-47.c: New testcase.

From-SVN: r94701
This commit is contained in:
Richard Guenther 2005-02-07 13:24:38 +00:00 committed by Richard Biener
parent 48c4e71107
commit 6a96f5c111
6 changed files with 47 additions and 7 deletions
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7
gcc/ChangeLog
View File

@ -1,3 +1,10 @@
2005-02-07 Richard Guenther <rguenth@gcc.gnu.org>
PR middle-end/19775
* builtins.c (fold_builtin_sqrt): Transform
sqrt(pow(x,y)) to pow(fabs(x),y*0.5), not
pow(x,y*0.5).
2005-02-07 Leehod Baruch <leehod@il.ibm.com>
Dorit Naishlos <dorit@il.ibm.com>

9
gcc/builtins.c
View File

@ -6186,7 +6186,7 @@ fold_builtin_sqrt (tree arglist, tree type)
}
}
/* Optimize sqrt(pow(x,y)) = pow(x,y*0.5). */
/* Optimize sqrt(pow(x,y)) = pow(|x|,y*0.5). */
if (flag_unsafe_math_optimizations
&& (fcode == BUILT_IN_POW
|| fcode == BUILT_IN_POWF
@ -6195,8 +6195,11 @@ fold_builtin_sqrt (tree arglist, tree type)
tree powfn = TREE_OPERAND (TREE_OPERAND (arg, 0), 0);
tree arg0 = TREE_VALUE (TREE_OPERAND (arg, 1));
tree arg1 = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (arg, 1)));
tree narg1 = fold (build2 (MULT_EXPR, type, arg1,
build_real (type, dconsthalf)));
tree narg1;
if (!tree_expr_nonnegative_p (arg0))
arg0 = build1 (ABS_EXPR, type, arg0);
narg1 = fold (build2 (MULT_EXPR, type, arg1,
build_real (type, dconsthalf)));
arglist = tree_cons (NULL_TREE, arg0,
build_tree_list (NULL_TREE, narg1));
return build_function_call_expr (powfn, arglist);

9
gcc/testsuite/ChangeLog
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@ -1,3 +1,12 @@
2005-02-07 Richard Guenther <rguenth@gcc.gnu.org>
PR middle-end/19775
* gcc.dg/torture/builtin-power-1.c: Disable test for
invalid transformation.
* gcc.dg/builtins-10.c: Likewise. Disable one test we
no longer optimize.
* gcc.dg/builtins-47.c: New testcase.
2005-02-07 Leehod Baruch <leehod@il.ibm.com>
Dorit Naishlos <dorit@il.ibm.com>

7
gcc/testsuite/gcc.dg/builtins-10.c
View File

@ -14,11 +14,12 @@ extern double exp(double);
extern double log(double);
extern double sqrt(double);
extern double pow(double,double);
extern double fabs(double);
void test(double x)
{
if (sqrt(pow(x,4.0)) != x*x)
link_error ();
/*if (sqrt(pow(x,4.0)) != x*x)
link_error (); */
if (pow(sqrt(x),4.0) != x*x)
link_error ();
@ -29,7 +30,7 @@ void test(double x)
void test2(double x, double y, double z)
{
if (sqrt(pow(x,y)) != pow(x,y*0.5))
if (sqrt(pow(x,y)) != pow(fabs(x),y*0.5))
link_error ();
if (log(pow(x,y)) != y*log(x))

20
gcc/testsuite/gcc.dg/builtins-47.c Normal file
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@ -0,0 +1,20 @@
/* { dg-do run } */
/* { dg-options "-ffast-math -fdump-tree-gimple" } */
extern double sqrt (double);
extern double pow (double, double);
extern void abort (void);
int main ()
{
double x = -1.0;
if (sqrt (pow (x, 2)) != 1.0)
abort();
if (sqrt (x*x) != 1.0)
abort();
return 0;
}
/* { dg-final { scan-tree-dump-times "sqrt" 0 "gimple" } } */
/* { dg-final { scan-tree-dump-times "pow" 0 "gimple" } } */

2
gcc/testsuite/gcc.dg/torture/builtin-power-1.c
View File

@ -63,7 +63,7 @@ void test(double d1, double d2, double d3,
|| FN##l(powl(ld1,ld2)) != powl(ld1,ld2/N)) \
link_failure_##FN##_pow()
ROOT_POW(sqrt,2);
/*ROOT_POW(sqrt,2); Invalid. */
/*ROOT_POW(cbrt,3); Intentionally not implemented. */
/* Test pow(pow(x,y),z) -> pow(x,y*z). */