From 495ed96c2a50e2ff9ce7b056ca6aea822090ed28 Mon Sep 17 00:00:00 2001
From: Uros Bizjak <uros@kss-loka.si>
Date: Sat, 21 Oct 2006 22:05:35 +0200
Subject: [PATCH] re PR middle-end/28252 (pow(x,1/3.0) should be converted to
 cbrt(x))

2006-10-21  Uros Bizjak  <uros@kss-loka.si>

        PR middle-end/28252
        * builtins.c (fold_builtin): Fold pow(x,1.0/3.0) as cbrt(x) if
        flag_unsafe_math_optimizations is set.

testsuite/ChangeLog:

        PR middle-end/28252
        * gcc.dg/builtins-8.c: Also check pow(x,1.0/3.0) to cbrt(x)
        transformation.

From-SVN: r117937
---
 gcc/ChangeLog                     |  6 ++++++
 gcc/builtins.c                    | 17 +++++++++++++++++
 gcc/testsuite/ChangeLog           |  6 ++++++
 gcc/testsuite/gcc.dg/builtins-8.c |  6 +++++-
 4 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 42b4dedc4f4..21550b3626f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -4,6 +4,12 @@
 	(expand_builtin): Use it to expand lrint instead of
 	expand_builtin_mathfn.
 
+2006-10-21  Uros Bizjak  <uros@kss-loka.si>
+
+	PR middle-end/28252
+	* builtins.c (fold_builtin): Fold pow(x,1.0/3.0) as cbrt(x) if
+	flag_unsafe_math_optimizations is set.
+
 2006-10-21  Uros Bizjak  <uros@kss-loka.si>
 
 	PR target/19398
diff --git a/gcc/builtins.c b/gcc/builtins.c
index c1996dc44b1..ecee42b69be 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -7775,6 +7775,23 @@ fold_builtin_pow (tree fndecl, tree arglist, tree type)
 	    }
 	}
 
+      /* Optimize pow(x,1.0/3.0) = cbrt(x).  */
+      if (flag_unsafe_math_optimizations)
+	{
+	  const REAL_VALUE_TYPE dconstroot
+	    = real_value_truncate (TYPE_MODE (type), dconstthird);
+
+	  if (REAL_VALUES_EQUAL (c, dconstroot))
+	    {
+	      tree cbrtfn = mathfn_built_in (type, BUILT_IN_CBRT);
+	      if (cbrtfn != NULL_TREE)
+		{
+		  tree arglist = build_tree_list (NULL_TREE, arg0);
+		  return build_function_call_expr (cbrtfn, arglist);
+		}
+	    }
+	}
+
       /* Check for an integer exponent.  */
       n = real_to_integer (&c);
       real_from_integer (&cint, VOIDmode, n, n < 0 ? -1 : 0, 0);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c30830dff1b..b55cd7c8f8b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2006-10-21  Uros Bizjak  <uros@kss-loka.si>
+
+	PR middle-end/28252
+	* gcc.dg/builtins-8.c: Also check pow(x,1.0/3.0) to cbrt(x)
+	transformation.
+
 2006-10-21  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/3511
diff --git a/gcc/testsuite/gcc.dg/builtins-8.c b/gcc/testsuite/gcc.dg/builtins-8.c
index c3066b41cab..be17774d526 100644
--- a/gcc/testsuite/gcc.dg/builtins-8.c
+++ b/gcc/testsuite/gcc.dg/builtins-8.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2003  Free Software Foundation.
+/* Copyright (C) 2003, 2006  Free Software Foundation.
 
    Verify that built-in math function constant folding of functions
    with one constant argument is correctly performed by the compiler.
@@ -11,6 +11,7 @@
 extern void abort(void);
 extern double pow(double, double);
 extern double sqrt(double);
+extern double cbrt(double);
 
 void test(double x)
 {
@@ -25,6 +26,9 @@ void test(double x)
 
   if (pow(x,0.5) != sqrt(x))
     abort ();
+
+  if (pow(x,1.0/3.0) != cbrt(x))
+    abort ();
 }
 
 int main()