[AArch64] Backport to gcc-7 PR71727 fix -mstrict-align

[Christophe Lyon]

Hi,

I've recently committed a follow-up fix for PR71727 for -mstrict-align
on aarch64 (r253242).
I think it would be appropriate to apply it to gcc-7-branch. The patch
from trunk applies cleanly to gcc-7-branch.

Although the original bug was reported against 4.9.4, 5.3.1, 6.1.0,
Naveen's patch was not backported to these branches, so it's not
appropriate to backport my patch there.

OK?

Thanks,

Christophe
-------------- next part --------------
2017-09-20  Christophe Lyon  <christophe.lyon@linaro.org>

	PR target/71727
	gcc/
	* config/aarch64/aarch64.c
	(aarch64_builtin_support_vector_misalignment): Always return false
	when misalignment is unknown.

	gcc/testsuite/
	* gcc.target/aarch64/pr71727-2.c: New test.
-------------- next part --------------
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 799989a..7cc67ec 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -11757,19 +11757,9 @@ aarch64_builtin_support_vector_misalignment (machine_mode mode,
       if (optab_handler (movmisalign_optab, mode) == CODE_FOR_nothing)
         return false;
 
+      /* Misalignment factor is unknown at compile time.  */
       if (misalignment == -1)
-	{
-	  /* Misalignment factor is unknown at compile time but we know
-	     it's word aligned.  */
-	  if (aarch64_simd_vector_alignment_reachable (type, is_packed))
-            {
-              int element_size = TREE_INT_CST_LOW (TYPE_SIZE (type));
-
-              if (element_size != 64)
-                return true;
-            }
-	  return false;
-	}
+	return false;
     }
   return default_builtin_support_vector_misalignment (mode, type, misalignment,
 						      is_packed);
diff --git a/gcc/testsuite/gcc.target/aarch64/pr71727-2.c b/gcc/testsuite/gcc.target/aarch64/pr71727-2.c
new file mode 100644
index 0000000..2bc803a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/pr71727-2.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-mstrict-align -O3" } */
+
+unsigned char foo(const unsigned char *buffer, unsigned int length)
+{
+  unsigned char sum;
+  unsigned int  count;
+
+  for (sum = 0, count = 0; count < length; count++) {
+    sum = (unsigned char) (sum + *(buffer + count));
+  }
+
+  return sum;
+}
+
+/* { dg-final { scan-assembler-times "and\tw\[0-9\]+, w\[0-9\]+, 15" 1 } } */