[PATCH, rs6000] new split pattern for TI to V1TI move [PR103124]

[HAO CHEN GUI <guihaoc@linux.ibm.com>]

Hi,
   This patch defines a new split pattern for TI to V1TI move. The pattern concatenates two subreg:DI of
a TI to a V2DI. With the pattern, the subreg pass can do register split for TI when there is a TI to V1TI
move. The patch optimizes one unnecessary "mr" out on P9. The new test case illustrates it.

   Bootstrapped and tested on powerpc64-linux BE and LE with no regressions. Is this okay for trunk?
Any recommendations? Thanks a lot.

ChangeLog
2021-12-13 Haochen Gui <guihaoc@linux.ibm.com>

gcc/
	* config/rs6000/vsx.md (split pattern for TI to V1TI move): Defined.

gcc/testsuite/
	* gcc.target/powerpc/pr103124.c: New testcase.


patch.diff
diff --git a/gcc/config/rs6000/vsx.md b/gcc/config/rs6000/vsx.md
index bf033e31c1c..52968eb4609 100644
--- a/gcc/config/rs6000/vsx.md
+++ b/gcc/config/rs6000/vsx.md
@@ -6589,3 +6589,19 @@ (define_insn "xxeval"
    [(set_attr "type" "vecperm")
     (set_attr "prefixed" "yes")])

+;; Construct V1TI by vsx_concat_v2di
+(define_split
+  [(set (match_operand:V1TI 0 "vsx_register_operand")
+	(subreg:V1TI
+	  (match_operand:TI 1 "int_reg_operand") 0 ))]
+  "TARGET_P9_VECTOR && !reload_completed"
+  [(const_int 0)]
+{
+  rtx tmp1 = simplify_gen_subreg (DImode, operands[1], TImode, 0);
+  rtx tmp2 = simplify_gen_subreg (DImode, operands[1], TImode, 8);
+  rtx tmp3 = gen_reg_rtx (V2DImode);
+  emit_insn (gen_vsx_concat_v2di (tmp3, tmp1, tmp2));
+  rtx tmp4 = simplify_gen_subreg (V1TImode, tmp3, V2DImode, 0);
+  emit_move_insn (operands[0], tmp4);
+  DONE;
+})
diff --git a/gcc/testsuite/gcc.target/powerpc/pr103124.c b/gcc/testsuite/gcc.target/powerpc/pr103124.c
new file mode 100644
index 00000000000..e9072d19b8e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr103124.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* { dg-require-effective-target int128 } */
+/* { dg-options "-O2 -mdejagnu-cpu=power9" } */
+/* { dg-final { scan-assembler-not "\mmr\M" } } */
+
+vector __int128 add (long long a)
+{
+  vector __int128 b;
+  b = (vector __int128) {a};
+  return b;
+}