middle-end/97521 - fix VECTOR_CST expansion

This fixes expansion of VECTOR_BOOLEAN_TYPE_P VECTOR_CSTs which
when using an integer mode are not always "mask-mode" but may
be using an integer mode when there's no supported vector mode.

The patch makes sure to only go the mask-mode expansion if
the elements do not line up to cover the full integer mode
(when they do and the mode was an actual mask-mode there's
no actual difference in both expansions).

2020-10-22  Richard Biener  <rguenther@suse.de>

	PR middle-end/97521
	* expr.c (expand_expr_real_1): Be more careful when
	expanding a VECTOR_BOOLEAN_TYPE_P VECTOR_CSTs.

	* gcc.target/i386/pr97521.c: New testcase.

2 files changed, 31 insertions, 1 deletions

diff --git a/gcc/expr.c b/gcc/expr.c
index 9d951e8..d87bda7 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -10356,7 +10356,10 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
 	scalar_int_mode int_mode;
 	if (is_int_mode (mode, &int_mode))
 	  {
-	    if (VECTOR_BOOLEAN_TYPE_P (TREE_TYPE (exp)))
+	    if (VECTOR_BOOLEAN_TYPE_P (TREE_TYPE (exp))
+		&& maybe_ne (TYPE_PRECISION (TREE_TYPE (TREE_TYPE (exp)))
+			     * TYPE_VECTOR_SUBPARTS (TREE_TYPE (exp)),
+			     GET_MODE_PRECISION (int_mode)))
 	      return const_scalar_mask_from_tree (int_mode, exp);
 	    else
 	      {
diff --git a/gcc/testsuite/gcc.target/i386/pr97521.c b/gcc/testsuite/gcc.target/i386/pr97521.c
new file mode 100644
index 0000000..804ffd6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr97521.c
@@ -0,0 +1,27 @@
+/* { dg-do run } */
+/* { dg-options "-O -mno-sse2" } */
+
+typedef unsigned char __attribute__ ((__vector_size__ (8))) V;
+typedef unsigned long long __attribute__ ((__vector_size__ (16))) W;
+
+V c;
+W d, e;
+
+V
+foo (W f)
+{
+  W g = (W) { 0, 209 } <7 <= (0 < f);
+  W h = e + g + d;
+  V j = (V) (h[0]) + (V) c;
+  return j;
+}
+
+int
+main (void)
+{
+  V x = foo ((W) { 3 });
+  for (unsigned i = 0; i < sizeof (x); i++)
+    if (x[i] != 0xff)
+      __builtin_abort ();
+  return 0;
+}