Fixed incorrect TARGET_MEM_REF alignment (PR 84419)

[Richard Sandiford <richard.sandiford@linaro.org>]

expand_call_mem_ref checks for TARGET_MEM_REFs that have compatible
type, but it didn't then go on to install the specific type we need,
which might have different alignment due to:

  if (TYPE_ALIGN (type) != align)
    type = build_aligned_type (type, align);

This was causing masked stores to be incorrectly marked as
aligned on AVX512.

Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64-linux-gnu.
Also tested by Alexander on AVX512 hw.  OK to install?

Richard


2018-02-20  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/84419
	* internal-fn.c (expand_call_mem_ref): Create a TARGET_MEM_REF
	with the required type if its current type is compatible but
	different.

gcc/testsuite/
	PR tree-optimization/84419
	* gcc.dg/vect/pr84419.c: New test.

Index: gcc/internal-fn.c
===================================================================
--- gcc/internal-fn.c	2018-01-13 18:01:51.235735290 +0000
+++ gcc/internal-fn.c	2018-02-20 09:40:47.547217244 +0000
@@ -2444,11 +2444,14 @@ expand_call_mem_ref (tree type, gcall *s
 	  && types_compatible_p (TREE_TYPE (mem), type))
 	{
 	  tree offset = TMR_OFFSET (mem);
-	  if (alias_ptr_type != TREE_TYPE (offset) || !integer_zerop (offset))
+	  if (type != TREE_TYPE (mem)
+	      || alias_ptr_type != TREE_TYPE (offset)
+	      || !integer_zerop (offset))
 	    {
 	      mem = copy_node (mem);
 	      TMR_OFFSET (mem) = wide_int_to_tree (alias_ptr_type,
 						   wi::to_poly_wide (offset));
+	      TREE_TYPE (mem) = type;
 	    }
 	  return mem;
 	}
Index: gcc/testsuite/gcc.dg/vect/pr84419.c
===================================================================
--- /dev/null	2018-02-19 19:34:42.906488063 +0000
+++ gcc/testsuite/gcc.dg/vect/pr84419.c	2018-02-20 09:40:47.548217201 +0000
@@ -0,0 +1,21 @@
+#include <string.h>
+
+#define SIZE 400
+
+int  foo[SIZE];
+char bar[SIZE];
+
+void __attribute__ ((noinline)) foo_func(void)
+{
+  int i;
+  for (i = 1; i < SIZE; i++)
+    if (bar[i])
+      foo[i] = 1;
+}
+
+int main()
+{
+  memset(bar, 1, sizeof(bar));
+  foo_func();
+  return 0;
+}