aarch64: -mstrict-align vs __arm_data512_t [PR113657]

After r14-1187-gd6b756447cd58b, simplify_gen_subreg can return
NULL for "unaligned" memory subreg. Since V8DI has an alignment of 8 bytes,
using TImode causes simplify_gen_subreg to return NULL.
This fixes the issue by using DImode instead for the loop. And then we will have
later on the STP/LDP pass combine it back into STP/LDP if needed.
Since strict align is less important (usually used for firmware and early boot only),
not doing LDP/STP here is ok.

Built and tested for aarch64-linux-gnu with no regressions.

	PR target/113657

gcc/ChangeLog:

	* config/aarch64/aarch64-simd.md (split for movv8di):
	For strict aligned mode, use DImode instead of TImode.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/acle/ls64_strict_align.c: New test.

Signed-off-by: Andrew Pinski <[email protected]>

Author: apinski-quic

gcc/config/aarch64/aarch64-simd.md

@@ -8221,14 +8221,17 @@
 	   || (memory_operand (operands[0], V8DImode)
 	       && register_operand (operands[1], V8DImode)))
     {
+      /* V8DI only guarantees 8-byte alignment, whereas TImode requires 16.  */
+      auto mode = STRICT_ALIGNMENT ? DImode : TImode;
+      int increment = GET_MODE_SIZE (mode);
       std::pair<rtx, rtx> last_pair = {};
-      for (int offset = 0; offset < 64; offset += 16)
+      for (int offset = 0; offset < 64; offset += increment)
         {
 	  std::pair<rtx, rtx> pair = {
-	    simplify_gen_subreg (TImode, operands[0], V8DImode, offset),
-	    simplify_gen_subreg (TImode, operands[1], V8DImode, offset)
+	    simplify_gen_subreg (mode, operands[0], V8DImode, offset),
+	    simplify_gen_subreg (mode, operands[1], V8DImode, offset)
 	  };
-	  if (register_operand (pair.first, TImode)
+	  if (register_operand (pair.first, mode)
 	      && reg_overlap_mentioned_p (pair.first, pair.second))
 	    last_pair = pair;
 	  else

gcc/testsuite/gcc.target/aarch64/acle/ls64_strict_align.c

@@ -0,0 +1,7 @@
+/* { dg-do compile } */
+/* { dg-options "-mstrict-align" } */
+/* PR target/113657 */
+
+#pragma GCC target "+ls64"
+#pragma GCC aarch64 "arm_acle.h"
+__arm_data512_t foo(__arm_data512_t* ptr) { return *ptr; }