patch from paul eggert to fix -0.0/0.0 confusion that breaks glibc

	* real.h (REAL_VALUES_IDENTICAL): New macro.
	* expr.c (is_zeros_p): Don't consider -0.0 to be all zeros.
	* fold-const.c (operand_equal_p): Don't consider -0.0 to be
	identical to 0.0.
	* tree.c (simple_cst_equal): Don't consider -0.0 to have the
	same tree structure as 0.0.
	* varasm.c (immed_real_const_1): Use new REAL_VALUES_IDENTICAL
	macro instead of doing it by hand.

From-SVN: r16472

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 79a5a8bbebc3f3930eb70786e898053447d92a90..12cac79d33c2c651f259e56f2c31aab711a2fbaa 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,18 @@
+1997-11-13  Paul Eggert  <eggert@twinsun.com>
+
+       Fix some confusion with IEEE minus zero.
+
+       * real.h (REAL_VALUES_IDENTICAL): New macro.
+
+       * expr.c (is_zeros_p): Don't consider -0.0 to be all zeros.
+       * fold-const.c (operand_equal_p): Don't consider -0.0 to be
+       identical to 0.0.
+       * tree.c (simple_cst_equal): Don't consider -0.0 to have the
+       same tree structure as 0.0.
+
+       * varasm.c (immed_real_const_1): Use new REAL_VALUES_IDENTICAL
+       macro instead of doing it by hand.
+
 Thu Nov 13 16:56:14 1997  Jeffrey A Law  (law@cygnus.com)
 
        * v850/lib1funcs.asm: Minor whitespace changes.

diff --git a/gcc/expr.c b/gcc/expr.c
index 2f28be5a3e43200755338dbd7d2fba21e2828772..a18b09e9aba7c71093b74e542d715648a743ab61 100644 (file)
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -3476,7 +3476,7 @@ is_zeros_p (exp)
        is_zeros_p (TREE_REALPART (exp)) && is_zeros_p (TREE_IMAGPART (exp));
 
     case REAL_CST:
-      return REAL_VALUES_EQUAL (TREE_REAL_CST (exp), dconst0);
+      return REAL_VALUES_IDENTICAL (TREE_REAL_CST (exp), dconst0);
 
     case CONSTRUCTOR:
       if (TREE_TYPE (exp) && TREE_CODE (TREE_TYPE (exp)) == SET_TYPE)

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 9b342528f8acd21b885adf2778d8707250e6c3b9..4b4c5e184b4c55e96ba3beb08585d16657ab9f75 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -1796,8 +1796,8 @@ operand_equal_p (arg0, arg1, only_const)
       case REAL_CST:
        return (! TREE_CONSTANT_OVERFLOW (arg0)
                && ! TREE_CONSTANT_OVERFLOW (arg1)
-               && REAL_VALUES_EQUAL (TREE_REAL_CST (arg0),
-                                     TREE_REAL_CST (arg1)));
+               && REAL_VALUES_IDENTICAL (TREE_REAL_CST (arg0),
+                                         TREE_REAL_CST (arg1)));
 
       case COMPLEX_CST:
        return (operand_equal_p (TREE_REALPART (arg0), TREE_REALPART (arg1),

diff --git a/gcc/real.h b/gcc/real.h
index 530a88659f72c5d890456e8d4246e69114a1aa95..a91061ef54d610e1f1a13a33cd1662cd5d9df3ad 100644 (file)
--- a/gcc/real.h
+++ b/gcc/real.h
@@ -294,6 +294,13 @@ do { REAL_VALUE_TYPE in = (IN);  /* Make sure it's not in a register.  */\
 #define REAL_VALUE_TO_TARGET_LONG_DOUBLE(a, b) REAL_VALUE_TO_TARGET_DOUBLE (a, b)
 #endif
 
+/* Compare two floating-point objects for bitwise identity.
+   This is not the same as comparing for equality on IEEE hosts:
+   -0.0 equals 0.0 but they are not identical, and conversely
+   two NaNs might be identical but they cannot be equal.  */
+#define REAL_VALUES_IDENTICAL(x, y) \
+  (!bcmp ((char *) &(x), (char *) &(y), sizeof (REAL_VALUE_TYPE)))
+
 /* Compare two floating-point values for equality.  */
 #ifndef REAL_VALUES_EQUAL
 #define REAL_VALUES_EQUAL(x, y) ((x) == (y))

diff --git a/gcc/tree.c b/gcc/tree.c
index 2129f8491e18593091ede447b5355ebec5983f08..ecd6961daf6ec4ba6c135bb3f4aa7a15ace766ee 100644 (file)
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -3840,7 +3840,7 @@ simple_cst_equal (t1, t2)
        && TREE_INT_CST_HIGH (t1) == TREE_INT_CST_HIGH (t2);
 
     case REAL_CST:
-      return REAL_VALUES_EQUAL (TREE_REAL_CST (t1), TREE_REAL_CST (t2));
+      return REAL_VALUES_IDENTICAL (TREE_REAL_CST (t1), TREE_REAL_CST (t2));
 
     case STRING_CST:
       return TREE_STRING_LENGTH (t1) == TREE_STRING_LENGTH (t2)

diff --git a/gcc/varasm.c b/gcc/varasm.c
index 1161837cec39ca013a245714cfd9e8b65b87558f..ab88bebb46f4259f650132de537abb4dbc5c4c95 100644 (file)
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -2245,8 +2245,7 @@ immed_real_const_1 (d, mode)
 
   /* Detect special cases.  */
 
-  /* Avoid REAL_VALUES_EQUAL here in order to distinguish minus zero.  */
-  if (!bcmp ((char *) &dconst0, (char *) &d, sizeof d))
+  if (REAL_VALUES_IDENTICAL (dconst0, d))
     return CONST0_RTX (mode);
   /* Check for NaN first, because some ports (specifically the i386) do not
      emit correct ieee-fp code by default, and thus will generate a core