* fold-const.c (fold <MULT_EXPR>): Optimize (C1/X)*C2 into

	(C1*C2)/X when unsafe math optimizations are allowed.
	(fold <RDIV_EXPR>): Optimize C1/(X*C2) into (C1/C2)/X with unsafe
	math optimizations.  Minor code clean-ups.  Recursively call
	fold when constructing sub-expressions.

	* gcc.dg/20030826-1.c: New test case.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@70807 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 78 insertions, 10 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6c195ba1f4e..1b7d9708fa6 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,13 @@
 2003-08-26  Roger Sayle  <roger@eyesopen.com>
 
+	* fold-const.c (fold <MULT_EXPR>): Optimize (C1/X)*C2 into
+	(C1*C2)/X when unsafe math optimizations are allowed.
+	(fold <RDIV_EXPR>): Optimize C1/(X*C2) into (C1/C2)/X with unsafe
+	math optimizations.  Minor code clean-ups.  Recursively call
+	fold when constructing sub-expressions.
+
+2003-08-26  Roger Sayle  <roger@eyesopen.com>
+
 	* builtins.c (fold_builtin_bitop): New function to perform constant
 	folding of ffs, clz, ctz, popcount and parity builtin functions
 	and their long and long long variants (such as ffsl and ffsll).
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 27a4724cabe..efa2db96637 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -6060,6 +6060,19 @@ fold (tree expr)
 	      && real_minus_onep (arg1))
 	    return fold (build1 (NEGATE_EXPR, type, arg0));
 
+	  /* Convert (C1/X)*C2 into (C1*C2)/X.  */
+	  if (flag_unsafe_math_optimizations
+	      && TREE_CODE (arg0) == RDIV_EXPR
+	      && TREE_CODE (arg1) == REAL_CST
+	      && TREE_CODE (TREE_OPERAND (arg0, 0)) == REAL_CST)
+	    {
+	      tree tem = const_binop (MULT_EXPR, TREE_OPERAND (arg0, 0),
+				      arg1, 0);
+	      if (tem)
+		return fold (build (RDIV_EXPR, type, tem,
+				    TREE_OPERAND (arg0, 1)));
+	    }
+
 	  if (flag_unsafe_math_optimizations)
 	    {
 	      enum built_in_function fcode0 = builtin_mathfn_code (arg0);
@@ -6393,7 +6406,7 @@ fold (tree expr)
 					  arg1, 0)))
 	    return fold (build (MULT_EXPR, type, arg0, tem));
 	  /* Find the reciprocal if optimizing and the result is exact.  */
-	  else if (optimize)
+	  if (optimize)
 	    {
 	      REAL_VALUE_TYPE r;
 	      r = TREE_REAL_CST (arg1);
@@ -6407,19 +6420,29 @@ fold (tree expr)
       /* Convert A/B/C to A/(B*C).  */
       if (flag_unsafe_math_optimizations
 	  && TREE_CODE (arg0) == RDIV_EXPR)
-	{
-	  return fold (build (RDIV_EXPR, type, TREE_OPERAND (arg0, 0),
-			      build (MULT_EXPR, type, TREE_OPERAND (arg0, 1),
-				     arg1)));
-	}
+	return fold (build (RDIV_EXPR, type, TREE_OPERAND (arg0, 0),
+			    fold (build (MULT_EXPR, type,
+					 TREE_OPERAND (arg0, 1), arg1))));
+
       /* Convert A/(B/C) to (A/B)*C.  */
       if (flag_unsafe_math_optimizations
 	  && TREE_CODE (arg1) == RDIV_EXPR)
+	return fold (build (MULT_EXPR, type,
+			    fold (build (RDIV_EXPR, type, arg0,
+					 TREE_OPERAND (arg1, 0))),
+			    TREE_OPERAND (arg1, 1)));
+
+      /* Convert C1/(X*C2) into (C1/C2)/X.  */
+      if (flag_unsafe_math_optimizations
+	  && TREE_CODE (arg1) == MULT_EXPR
+	  && TREE_CODE (arg0) == REAL_CST
+	  && TREE_CODE (TREE_OPERAND (arg1, 1)) == REAL_CST)
 	{
-	  return fold (build (MULT_EXPR, type,
-			      build (RDIV_EXPR, type, arg0,
-				     TREE_OPERAND (arg1, 0)),
-			      TREE_OPERAND (arg1, 1)));
+	  tree tem = const_binop (RDIV_EXPR, arg0,
+				  TREE_OPERAND (arg1, 1), 0);
+	  if (tem)
+	    return fold (build (RDIV_EXPR, type, tem,
+				TREE_OPERAND (arg1, 0)));
 	}
 
       if (flag_unsafe_math_optimizations)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 1543516bedf..ba803a16550 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2003-08-26  Roger Sayle  <roger@eyesopen.com>
+
+	* gcc.dg/20030826-1.c: New test case.
+
 2003-08-26  Matt Kraai  <kraai@alumni.cmu.edu>
 
 	* gcc.dg/noncompile/20030818-1.c: Expect second line of error.
diff --git a/gcc/testsuite/gcc.dg/20030826-1.c b/gcc/testsuite/gcc.dg/20030826-1.c
new file mode 100644
index 00000000000..b344ad2dcbc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/20030826-1.c
@@ -0,0 +1,33 @@
+/* Copyright (C) 2003 Free Software Foundation.
+
+   Check that constant folding of mathematical expressions doesn't
+   break anything.
+
+   Written by Roger Sayle, 24th August 2003.  */
+
+/* { dg-do run } */
+/* { dg-options "-O2 -ffast-math" } */
+
+void abort(void);
+
+double foo(double x)
+{
+  return 12.0/(x*3.0);
+}
+
+double bar(double x)
+{
+  return (3.0/x)*4.0;
+}
+
+int main()
+{
+  if (foo(2.0) != 2.0)
+    abort ();
+
+  if (bar(2.0) != 6.0)
+    abort ();
+
+  return 0;
+}
+