* builtins.c (expand_builtin): Use expand_builtin_pow to expand

	calls for pow, powf, powl and their __builtin_ variants.
	(expand_builtin_pow): If the second argument is a constant
	integer and compiling with -ffast-math, use expand_powi to
	generate RTL if powi_cost is less than POWI_MAX_MULTS.
	(powi_cost): New function to return the number of multiplications
	necessary to evaluate an Nth power, for integer constant N.
	(expand_powi): New function to expand the RTL for evaluating
	the Nth power of a floating point value, for integer constant N.

	* doc/tm.texi (POWI_MAX_MULTS): Document new target macro.

	* gcc.dg/builtins-24.c: New test case.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@68401 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 35 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/builtins-24.c b/gcc/testsuite/gcc.dg/builtins-24.c
new file mode 100644
index 00000000000..41ec1889f5f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtins-24.c
@@ -0,0 +1,35 @@
+/* Copyright (C) 2003 Free Software Foundation.
+
+   Check that the RTL expansion of floating point exponentiation by
+   a constant integer doesn't break anything and produces the expected
+   results.
+
+   Written by Roger Sayle, 20th June 2003.  */
+
+/* { dg-do run } */
+/* { dg-options "-O2 -ffast-math" } */
+
+extern double pow(double,double);
+extern void abort(void);
+
+double foo (double x)
+{
+  return pow (x, 6);
+}
+
+double bar (double x)
+{
+  return pow (x, -4);
+}
+
+int main()
+{
+  if (foo (2.0) != 64.0)
+    abort ();
+
+  if (bar (2.0) != 0.0625)
+    abort ();
+
+  return 0;
+}
+