Re: [C/C++ PATCH] Don't emit invalid VEC_COND_EXPR for vector comparisons (PR c/68062)

[Marek Polacek <polacek at redhat dot com>]

On Wed, Jan 13, 2016 at 06:53:06PM +0000, Joseph Myers wrote:
> Will -Wsign-compare warnings be generated for the implicit signed / 
> unsigned conversions in comparisons, as for scalar comparisons?

Good point.  No, with the previous patch -Wsign-compare would be quiet.  But
since it probably should warn, I've added the warning (warn_for_sign_compare
isn't prepared to handle vectors so I've just used warning_at).

Regtested on x86_64-linux, bootstrap in progress, but I don't expect any
problems.

Ok for trunk?  What about branches, is this suitable for 5?

2016-01-13  Marek Polacek  <polacek@redhat.com>

	PR c/68062
	* c-typeck.c (build_binary_op) [EQ_EXPR, GE_EXPR]: Promote operand
	to unsigned, if needed.  Add -Wsign-compare warning.

	* typeck.c (cp_build_binary_op): Promote operand to unsigned, if
	needed.  Add -Wsign-compare warning.

	* c-c++-common/vector-compare-4.c: New test.

diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index 952041b..0fe1d46 100644
--- gcc/c/c-typeck.c
+++ gcc/c/c-typeck.c
@@ -11048,6 +11048,20 @@ build_binary_op (location_t location, enum tree_code code,
               return error_mark_node;
             }
 
+	  /* It's not precisely specified how the usual arithmetic
+	     conversions apply to the vector types.  Here, we use
+	     the unsigned type if one of the operands is signed and
+	     the other one is unsigned.  */
+	  if (TYPE_UNSIGNED (type0) != TYPE_UNSIGNED (type1))
+	    {
+	      if (!TYPE_UNSIGNED (type0))
+		op0 = build1 (VIEW_CONVERT_EXPR, type1, op0);
+	      else
+		op1 = build1 (VIEW_CONVERT_EXPR, type0, op1);
+	      warning_at (location, OPT_Wsign_compare, "comparison between "
+			  "types %qT and %qT", type0, type1);
+	    }
+
           /* Always construct signed integer vector type.  */
           intt = c_common_type_for_size (GET_MODE_BITSIZE
 					   (TYPE_MODE (TREE_TYPE (type0))), 0);
@@ -11201,6 +11215,20 @@ build_binary_op (location_t location, enum tree_code code,
               return error_mark_node;
             }
 
+	  /* It's not precisely specified how the usual arithmetic
+	     conversions apply to the vector types.  Here, we use
+	     the unsigned type if one of the operands is signed and
+	     the other one is unsigned.  */
+	  if (TYPE_UNSIGNED (type0) != TYPE_UNSIGNED (type1))
+	    {
+	      if (!TYPE_UNSIGNED (type0))
+		op0 = build1 (VIEW_CONVERT_EXPR, type1, op0);
+	      else
+		op1 = build1 (VIEW_CONVERT_EXPR, type0, op1);
+	      warning_at (location, OPT_Wsign_compare, "comparison between "
+			  "types %qT and %qT", type0, type1);
+	    }
+
           /* Always construct signed integer vector type.  */
           intt = c_common_type_for_size (GET_MODE_BITSIZE
 					   (TYPE_MODE (TREE_TYPE (type0))), 0);
diff --git gcc/cp/typeck.c gcc/cp/typeck.c
index 472b41b..2f0035a 100644
--- gcc/cp/typeck.c
+++ gcc/cp/typeck.c
@@ -4813,6 +4813,20 @@ cp_build_binary_op (location_t location,
 	      return error_mark_node;
 	    }
 
+	  /* It's not precisely specified how the usual arithmetic
+	     conversions apply to the vector types.  Here, we use
+	     the unsigned type if one of the operands is signed and
+	     the other one is unsigned.  */
+	  if (TYPE_UNSIGNED (type0) != TYPE_UNSIGNED (type1))
+	    {
+	      if (!TYPE_UNSIGNED (type0))
+		op0 = build1 (VIEW_CONVERT_EXPR, type1, op0);
+	      else
+		op1 = build1 (VIEW_CONVERT_EXPR, type0, op1);
+	      warning_at (location, OPT_Wsign_compare, "comparison between "
+			  "types %qT and %qT", type0, type1);
+	    }
+
 	  /* Always construct signed integer vector type.  */
 	  intt = c_common_type_for_size (GET_MODE_BITSIZE
 					   (TYPE_MODE (TREE_TYPE (type0))), 0);
diff --git gcc/testsuite/c-c++-common/vector-compare-4.c gcc/testsuite/c-c++-common/vector-compare-4.c
index e69de29..b44f474 100644
--- gcc/testsuite/c-c++-common/vector-compare-4.c
+++ gcc/testsuite/c-c++-common/vector-compare-4.c
@@ -0,0 +1,42 @@
+/* PR c/68062 */
+/* { dg-do compile } */
+/* { dg-options "-Wsign-compare" } */
+
+typedef signed char __attribute__ ((vector_size (4))) v4qi;
+typedef unsigned char __attribute__ ((vector_size (4))) uv4qi;
+typedef signed int __attribute__ ((vector_size (4 * __SIZEOF_INT__))) v4si;
+typedef unsigned int __attribute__ ((vector_size (4 * __SIZEOF_INT__))) uv4si;
+
+v4qi
+fn1 (void)
+{
+  v4qi a = { 1, 2, 3, 4 };
+  uv4qi b = { 4, 3, 2, 1 };
+  v4qi v = { 0, 0, 0, 0 };
+
+  v += (a == b); /* { dg-warning "comparison between types" } */
+  v += (a != b); /* { dg-warning "comparison between types" } */
+  v += (a >= b); /* { dg-warning "comparison between types" } */
+  v += (a <= b); /* { dg-warning "comparison between types" } */
+  v += (a > b); /* { dg-warning "comparison between types" } */
+  v += (a < b); /* { dg-warning "comparison between types" } */
+
+  return v;
+}
+
+v4si
+fn2 (void)
+{
+  v4si a = { 1, 2, 3, 4 };
+  uv4si b = { 4, 3, 2, 1 };
+  v4si v = { 0, 0, 0, 0 };
+
+  v += (a == b); /* { dg-warning "comparison between types" } */
+  v += (a != b); /* { dg-warning "comparison between types" } */
+  v += (a >= b); /* { dg-warning "comparison between types" } */
+  v += (a <= b); /* { dg-warning "comparison between types" } */
+  v += (a > b); /* { dg-warning "comparison between types" } */
+  v += (a < b); /* { dg-warning "comparison between types" } */
+
+  return v;
+}

	Marek