From 437f1df1afacb10132608f3cf27f4289c1bdbe1c Mon Sep 17 00:00:00 2001
From: Roger Sayle <roger@eyesopen.com>
Date: Fri, 7 Jun 2002 23:42:53 +0000
Subject: fold-const.c (fold): Place both integer and real constants last in
 comparisons.

	* fold-const.c (fold) [EQ_EXPR]:  Place both integer and real
	constants last in comparisons.  Optimize (x+1.0)>0.0 into the
	equivalent x > -1.0 when -ffast-math.

	* gcc.dg/20020607-2.c: New test case.

From-SVN: r54356
---
 gcc/fold-const.c | 39 ++++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)

(limited to 'gcc/fold-const.c')

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 6febe58..db41564 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -5814,6 +5814,20 @@ fold (expr)
     case GT_EXPR:
     case LE_EXPR:
     case GE_EXPR:
+      /* If one arg is a real or integer constant, put it last.  */
+      if ((TREE_CODE (arg0) == INTEGER_CST
+	   && TREE_CODE (arg1) != INTEGER_CST)
+	  || (TREE_CODE (arg0) == REAL_CST
+	      && TREE_CODE (arg0) != REAL_CST))
+	{
+	  TREE_OPERAND (t, 0) = arg1;
+	  TREE_OPERAND (t, 1) = arg0;
+	  arg0 = TREE_OPERAND (t, 0);
+	  arg1 = TREE_OPERAND (t, 1);
+	  code = swap_tree_comparison (code);
+	  TREE_SET_CODE (t, code);
+	}
+
       if (FLOAT_TYPE_P (TREE_TYPE (arg0)))
 	{
 	  /* (-a) CMP (-b) -> b CMP a  */
@@ -5835,18 +5849,21 @@ fold (expr)
 	      && REAL_VALUE_MINUS_ZERO (TREE_REAL_CST (arg1)))
 	    return fold (build (code, type, arg0,
 				build_real (TREE_TYPE (arg1), dconst0)));
-	}
 
-      /* If one arg is a constant integer, put it last.  */
-      if (TREE_CODE (arg0) == INTEGER_CST
-	  && TREE_CODE (arg1) != INTEGER_CST)
-	{
-	  TREE_OPERAND (t, 0) = arg1;
-	  TREE_OPERAND (t, 1) = arg0;
-	  arg0 = TREE_OPERAND (t, 0);
-	  arg1 = TREE_OPERAND (t, 1);
-	  code = swap_tree_comparison (code);
-	  TREE_SET_CODE (t, code);
+	  /* If this is a comparison of a real constant with a PLUS_EXPR
+	     or a MINUS_EXPR of a real constant, we can convert it into a
+	     comparison with a revised real constant as long as no overflow
+	     occurs when unsafe_math_optimizations are enabled.  */
+	  if (flag_unsafe_math_optimizations
+	      && TREE_CODE (arg1) == REAL_CST
+	      && (TREE_CODE (arg0) == PLUS_EXPR
+		  || TREE_CODE (arg0) == MINUS_EXPR)
+	      && TREE_CODE (TREE_OPERAND (arg0, 1)) == REAL_CST
+	      && 0 != (tem = const_binop (TREE_CODE (arg0) == PLUS_EXPR
+					  ? MINUS_EXPR : PLUS_EXPR,
+					  arg1, TREE_OPERAND (arg0, 1), 0))
+	      && ! TREE_CONSTANT_OVERFLOW (tem))
+	    return fold (build (code, type, TREE_OPERAND (arg0, 0), tem));
 	}
 
       /* Convert foo++ == CONST into ++foo == CONST + INCR.
-- 
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