[PATCHv2, rs6000] Merge two vector shift when their sources are the same

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

Hi,
  This patch merges two "vsldoi" insns when their sources are the
same. Particularly, it is simplified to be one move if the total
shift is multiples of 16 bytes.

  Bootstrapped and tested on powerpc64-linux BE and LE with no
regressions.

Thanks
Gui Haochen


ChangeLog
2023-02-28  Haochen Gui <guihaoc@linux.ibm.com>

gcc/
	* config/rs6000/altivec.md (*altivec_vsldoi_dup_<mode>): New
	insn_and_split to merge two vsldoi when the sources are the same.

gcc/testsuite/
	* gcc.target/powerpc/vsldoi_merge.c: New.



patch.diff
diff --git a/gcc/config/rs6000/altivec.md b/gcc/config/rs6000/altivec.md
index 84660073f32..fae8ec2b2e8 100644
--- a/gcc/config/rs6000/altivec.md
+++ b/gcc/config/rs6000/altivec.md
@@ -2529,6 +2529,35 @@ (define_insn "altivec_vsldoi_<mode>"
   "vsldoi %0,%1,%2,%3"
   [(set_attr "type" "vecperm")])

+(define_insn_and_split "*altivec_vsldoi_dup_<mode>"
+  [(set (match_operand:VM 0 "register_operand" "=v")
+	(unspec:VM [(unspec:VM [(match_operand:VM 1 "register_operand" "v")
+				(match_dup 1)
+				(match_operand:QI 2 "immediate_operand" "i")]
+			       UNSPEC_VSLDOI)
+		    (unspec:VM [(match_dup 1)
+				(match_dup 1)
+				(match_dup 2)]
+			       UNSPEC_VSLDOI)
+		    (match_operand:QI 3 "immediate_operand" "i")]
+		   UNSPEC_VSLDOI))]
+  "TARGET_ALTIVEC"
+  "#"
+  "&& 1"
+  [(const_int 0)]
+{
+  unsigned int shift1 = UINTVAL (operands[2]);
+  unsigned int shift2 = UINTVAL (operands[3]);
+
+  unsigned int shift = (shift1 + shift2) % 16;
+  if (shift)
+    emit_insn (gen_altivec_vsldoi_<mode> (operands[0], operands[1],
+					  operands[1], GEN_INT (shift)));
+  else
+    emit_move_insn (operands[0], operands[1]);
+  DONE;
+})
+
 (define_insn "altivec_vupkhs<VU_char>"
   [(set (match_operand:VP 0 "register_operand" "=v")
 	(unspec:VP [(match_operand:<VP_small> 1 "register_operand" "v")]
diff --git a/gcc/testsuite/gcc.target/powerpc/vsldoi_merge.c b/gcc/testsuite/gcc.target/powerpc/vsldoi_merge.c
new file mode 100644
index 00000000000..eebd7b4d382
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/vsldoi_merge.c
@@ -0,0 +1,59 @@
+/* { dg-do run } */
+/* { dg-require-effective-target powerpc_vsx_ok } */
+/* { dg-options "-O2 -mvsx -save-temps" } */
+
+#include "altivec.h"
+
+#ifdef DEBUG
+#include <stdio.h>
+#endif
+
+void abort (void);
+
+__attribute__ ((noipa)) vector signed int
+test1 (vector signed int a)
+{
+  a = vec_sld (a, a, 2);
+  a = vec_sld (a, a, 6);
+  return a;
+}
+
+__attribute__ ((noipa)) vector signed int
+test2 (vector signed int a)
+{
+  a = vec_sld (a, a, 14);
+  a = vec_sld (a, a, 2);
+  return a;
+}
+
+int main (void)
+{
+  vector signed int a = {1,2,3,4};
+  vector signed int result_a;
+  int i;
+
+  result_a = test1 (a);
+  vector signed int expect_a = {3,4,1,2};
+
+  for (i = 0; i< 4; i++)
+    if (result_a[i] != expect_a[i])
+#ifdef DEBUG
+      printf("ERROR: test1 result[%d] = %d, not expected[%d] = %d\n",
+              i, result_a[i], i, expect_a[i]);
+#else
+      abort ();
+#endif
+
+  result_a = test2 (a);
+
+  for (i = 0; i< 4; i++)
+    if (result_a[i] != a[i])
+#ifdef DEBUG
+      printf("ERROR: test2 result[%d] = %d, not expected[%d] = %d\n",
+              i, result_a[i], i, a[i]);
+#else
+      abort ();
+#endif
+}
+
+/* { dg-final { scan-assembler-times {\mvsldoi\M} 1 } } */