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

4 files changed, 112 insertions, 11 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index db56e7f..afff77b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2002-06-07  Roger Sayle  <roger@eyesopen.com>
+
+	* 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.
+
 2002-06-07  Jason Thorpe  <thorpej@wasabisystems.com>
 
 	* config.gcc (mips*-*-netbsd*): Add mips/t-netbsd to ${tmake_file}.
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.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 576ef54..ea104cf 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2002-06-07  Roger Sayle  <roger@eyesopen.com>
+
+	* gcc.dg/20020607-2.c: New test case.
+
 2002-06-07  Jakub Jelinek  <jakub@redhat.com>
 
 	* gcc.c-torture/compile/20020604-1.c: New test.
diff --git a/gcc/testsuite/gcc.dg/20020607-2.c b/gcc/testsuite/gcc.dg/20020607-2.c
new file mode 100644
index 0000000..239aa9b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/20020607-2.c
@@ -0,0 +1,74 @@
+/* Copyright (C) 2002 Free Software Foundation.
+
+   Test for correctness of floating point comparisons.
+
+   Written by Roger Sayle, 3rd June 2002.  */
+
+/* { dg-do run } */
+/* { dg-options "-O2 -ffast-math" } */
+
+extern void abort (void);
+
+int test1 (double x, int ok)
+{
+  if ((x - 1.0) > 0.0)
+    {
+      if (!ok) abort ();
+    }
+  else
+    if (ok) abort ();
+}
+
+int test1f (float x, int ok)
+{
+  if ((x - 1.0f) > 0.0f)
+    {
+      if (!ok) abort ();
+    }
+  else
+    if (ok) abort ();
+}
+
+int test2 (double x, int ok)
+{
+  if ((x + 1.0) < 0.0)
+    {
+      if (!ok) abort ();
+    }
+  else
+    if (ok) abort ();
+}
+
+int test2f (float x, int ok)
+{
+  if ((x + 1.0f) < 0.0f)
+    {
+      if (!ok) abort ();
+    }
+  else
+    if (ok) abort ();
+}
+
+
+int
+main ()
+{
+  test1 (-2.0, 0);
+  test1 ( 0.0, 0);
+  test1 ( 2.0, 1);
+
+  test1f (-2.0f, 0);
+  test1f ( 0.0f, 0);
+  test1f ( 2.0f, 1);
+
+  test2 (-2.0, 1);
+  test2 ( 0.0, 0);
+  test2 ( 2.0, 0);
+
+  test2f (-2.0f, 1);
+  test2f ( 0.0f, 0);
+  test2f ( 2.0f, 0);
+
+  return 0;
+}
+