* fold-const.c (fold <MULT_EXPR>): Optimize both x*pow(x,c) and

	pow(x,c)*x as pow(x,c+1) for constant values c.  Optimize x*x
	as pow(x,2.0) when the latter will be expanded back into x*x.
	(fold <RDIV_EXPR>): Optimize pow(x,c)/x as pow(x,c-1).
	* builtins.c (expand_builtin_pow): Ignore flag_errno_math as
	pow can never set errno when used with an integer exponent.
	Always use expand_powi when exponent is -1, 0, 1 or 2.
	(fold_builtin): Don't rewrite pow(x,2.0) as x*x nor pow(x,-2.0)
	as 1.0/(x*x).  This avoids unbounded recursion as we now prefer
	the pow forms of these expressions.

	* gcc.dg/builtins-27.c: New test case.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@70030 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 47 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/builtins-27.c b/gcc/testsuite/gcc.dg/builtins-27.c
new file mode 100644
index 00000000000..69d8f994481
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtins-27.c
@@ -0,0 +1,47 @@
+/* Copyright (C) 2003 Free Software Foundation.
+
+   Check that constant folding of built-in math functions doesn't
+   break anything and produces the expected results.
+
+   Written by Roger Sayle, 29th July 2003.  */
+
+/* { dg-do link } */
+/* { dg-options "-O2 -ffast-math" } */
+
+extern void link_error(void);
+
+extern double pow(double,double);
+
+void test(double x)
+{
+  if (pow(x,2.0) != x*x)
+    link_error ();
+
+  if (x*pow(x,2.0) != pow(x,3.0))
+    link_error ();
+
+  if (pow(x,2.0)*x != pow(x,3.0))
+    link_error ();
+
+  if (pow(x,3.0) != x*x*x)
+    link_error ();
+
+  if (pow(x,2.0)*x != x*x*x)
+    link_error ();
+
+  if (x*pow(x,2.0) != x*x*x)
+    link_error ();
+
+  if (pow(x,3.0)/x != pow(x,2.0))
+    link_error ();
+
+  if (pow(x,3.0)/x != x*x)
+    link_error ();
+}
+
+int main()
+{
+  test (2.0);
+  return 0;
+}
+