re PR target/79971 (ICE in const_binop, at fold-const.c:1554 on ARM target with saturated integers)

2017-03-09  Richard Biener  <rguenther@suse.de>

	PR middle-end/79971
	* gimple-expr.c (useless_type_conversion_p): Preserve
	TYPE_SATURATING for fixed-point types.

	* gcc.dg/fixed-point/pr79971.c: New testcase.

From-SVN: r246002

gcc/ChangeLog

 2017-03-09  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/79971
+	* gimple-expr.c (useless_type_conversion_p): Preserve
+	TYPE_SATURATING for fixed-point types.
+
+2017-03-09  Richard Biener  <rguenther@suse.de>
+
 	PR ipa/79970
 	* ipa-prop.c (ipa_modify_formal_parameters): Avoid changing
 	alignment of BLKmode params.

gcc/gimple-expr.c

@@ -124,7 +124,7 @@ useless_type_conversion_p (tree outer_type, tree inner_type)
   /* Fixed point types with the same mode are compatible.  */
   else if (FIXED_POINT_TYPE_P (inner_type)
 	   && FIXED_POINT_TYPE_P (outer_type))
-    return true;
+    return TYPE_SATURATING (inner_type) == TYPE_SATURATING (outer_type);
 
   /* We need to take special care recursing to pointed-to types.  */
   else if (POINTER_TYPE_P (inner_type)

gcc/testsuite/ChangeLog

 2017-03-09  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/79971
+	* gcc.dg/fixed-point/pr79971.c: New testcase.
+
+2017-03-09  Richard Biener  <rguenther@suse.de>
+
 	PR ipa/79970
 	* gcc.dg/torture/pr79970.c: New testcase.
 

gcc/testsuite/gcc.dg/fixed-point/pr79971.c

+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+void
+a ()
+{
+  unsigned _Accum b;
+  for (b = 0.1; b; b += 0.1uk)
+    {
+      _Sat unsigned _Accum b;
+      for (b = 0; b <= 0.8; b = 0.1)
+	;
+    }
+}