rename mod_honor_signed_zeros() -> mode_has_signed_zero() and fix it

include/libfirm/irmode.h

@@ -359,10 +359,11 @@ FIRM_API ir_mode *find_signed_mode(const ir_mode *mode);
 FIRM_API ir_mode *find_double_bits_int_mode(const ir_mode *mode);
 
 /**
- * Returns non-zero if the given mode honors signed zero's, i.e.,
- * a +0 and a -0 exists and handled differently.
+ * Returns non-zero if the given mode has negative zeros, i.e. +0 and -0 exist.
+ * Note that for comparisons +0 and -0 are considered equal, the sign only
+ * shows in expressions like 1/x which results in +inf/-inf.
  */
-FIRM_API int mode_honor_signed_zeros(const ir_mode *mode);
+FIRM_API int mode_has_signed_zero(const ir_mode *mode);
 
 /**
  * Returns non-zero if the given mode might overflow on unary Minus.

ir/ir/irmode.c

@@ -620,14 +620,17 @@ ir_mode *find_double_bits_int_mode(const ir_mode *mode)
 	return find_mode(&n);
 }
 
-int mode_honor_signed_zeros(const ir_mode *mode)
-{
-	/* for floating point, we know that IEEE 754 has +0 and -0,
-	 * but always handles it identical.
-	 */
-	return
-		mode->sort == irms_float_number &&
-		mode->arithmetic != irma_ieee754;
+int mode_has_signed_zero(const ir_mode *mode)
+{
+	switch (mode->arithmetic) {
+	case irma_ieee754:
+	case irma_x86_extended_float:
+		return 1;
+	case irma_none:
+	case irma_twos_complement:
+		return 0;
+	}
+	panic("invalid mode arithmetic");
 }
 
 int mode_overflow_on_unary_Minus(const ir_mode *mode)

ir/ir/iropt.c

@@ -1258,7 +1258,7 @@ static ir_node *equivalent_node_Mux(ir_node *n)
 		DBG_OPT_ALGSIM0(oldn, n, FS_OPT_MUX_EQ);
 		return n;
 	}
-	if (is_Cmp(sel) && !mode_honor_signed_zeros(get_irn_mode(n))) {
+	if (is_Cmp(sel) && !mode_has_signed_zero(get_irn_mode(n))) {
 		ir_relation relation = get_Cmp_relation(sel);
 		ir_node    *f        = get_Mux_false(n);
 		ir_node    *t        = get_Mux_true(n);
@@ -5412,7 +5412,7 @@ int ir_mux_is_abs(const ir_node *sel, const ir_node *mux_false,
 	 * transformations.
 	 */
 	mode = get_irn_mode(mux_true);
-	if (mode_honor_signed_zeros(mode))
+	if (mode_has_signed_zero(mode))
 		return 0;
 
 	/* must be <, <=, >=, > */