Hi,

  The patch optimized for vec_reve builtin on rs6000. For V2DI and V2DF, it is implemented by xxswapd on all targets. For V16QI, V8HI, V4SI and V4SF, it is implemented by quadword byte reverse plus halfword/word byte reverse when p9_vector is set.

  Bootstrapped and tested on powerpc64le-linux with no regressions. Is this okay for trunk? Any recommendations? Thanks a lot.

ChangeLog
2021-11-17 Haochen Gui <guihaoc@linux.ibm.com>

gcc/
        * config/rs6000/altivec.md (altivec_vreve<mode>2 for VEC_K): Use
        xxbrq for v16qi, xxbrq + xxbrh for v8hi and xxbrq + xxbrw for v4si
        or v4sf when p9_vector is set.
        (altivec_vreve<mode>2 for VEC_64): Defined. Implemented by xxswapd.

gcc/testsuite/
        * gcc.target/powerpc/vec_reve_1.c: New test.
        * gcc.target/powerpc/vec_reve_2.c: Likewise.

patch.diff
diff --git a/gcc/config/rs6000/altivec.md b/gcc/config/rs6000/altivec.md
index 1351dafbc41..a1698ce85c0 100644
--- a/gcc/config/rs6000/altivec.md
+++ b/gcc/config/rs6000/altivec.md
@@ -4049,13 +4049,43 @@ (define_expand "altivec_negv4sf2"
   DONE;
 })

-;; Vector reverse elements
+;; Vector reverse elements for V16QI V8HI V4SI V4SF
 (define_expand "altivec_vreve<mode>2"
-  [(set (match_operand:VEC_A 0 "register_operand" "=v")
-       (unspec:VEC_A [(match_operand:VEC_A 1 "register_operand" "v")]
+  [(set (match_operand:VEC_K 0 "register_operand" "=v")
+       (unspec:VEC_K [(match_operand:VEC_K 1 "register_operand" "v")]
                      UNSPEC_VREVEV))]
   "TARGET_ALTIVEC"
 {
+  if (TARGET_P9_VECTOR)
+    {
+      if (<MODE>mode == V16QImode)
+       emit_insn (gen_p9_xxbrq_v16qi (operands[0], operands[1]));
+      else if (<MODE>mode == V8HImode)
+       {
+         rtx subreg1 = simplify_gen_subreg (V1TImode, operands[1],
+                                            <MODE>mode, 0);
+         rtx temp = gen_reg_rtx (V1TImode);
+         emit_insn (gen_p9_xxbrq_v1ti (temp, subreg1));
+         rtx subreg2 = simplify_gen_subreg (<MODE>mode, temp,
+                                            V1TImode, 0);
+         emit_insn (gen_p9_xxbrh_v8hi (operands[0], subreg2));
+       }
+      else /* V4SI and V4SF.  */
+       {
+         rtx subreg1 = simplify_gen_subreg (V1TImode, operands[1],
+                                            <MODE>mode, 0);
+         rtx temp = gen_reg_rtx (V1TImode);
+         emit_insn (gen_p9_xxbrq_v1ti (temp, subreg1));
+         rtx subreg2 = simplify_gen_subreg (<MODE>mode, temp,
+                                            V1TImode, 0);
+         if (<MODE>mode == V4SImode)
+           emit_insn (gen_p9_xxbrw_v4si (operands[0], subreg2));
+         else
+           emit_insn (gen_p9_xxbrw_v4sf (operands[0], subreg2));
+       }
+      DONE;
+    }
+
   int i, j, size, num_elements;
   rtvec v = rtvec_alloc (16);
   rtx mask = gen_reg_rtx (V16QImode);
@@ -4074,6 +4104,17 @@ (define_expand "altivec_vreve<mode>2"
   DONE;
 })

+;; Vector reverse elements for V2DI V2DF
+(define_expand "altivec_vreve<mode>2"
+  [(set (match_operand:VEC_64 0 "register_operand" "=v")
+       (unspec:VEC_64 [(match_operand:VEC_64 1 "register_operand" "v")]
+                     UNSPEC_VREVEV))]
+  "TARGET_ALTIVEC"
+{
+  emit_insn (gen_xxswapd_<mode> (operands[0], operands[1]));
+  DONE;
+})
+
 ;; Vector SIMD PEM v2.06c defines LVLX, LVLXL, LVRX, LVRXL,
 ;; STVLX, STVLXL, STVVRX, STVRXL are available only on Cell.
 (define_insn "altivec_lvlx"
diff --git a/gcc/testsuite/gcc.target/powerpc/vec_reve_1.c b/gcc/testsuite/gcc.target/powerpc/vec_reve_1.c
new file mode 100644
index 00000000000..83a9206758b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/vec_reve_1.c
@@ -0,0 +1,16 @@
+/* { dg-require-effective-target powerpc_altivec_ok } */
+/* { dg-options "-O2 -maltivec" } */
+
+#include <altivec.h>
+
+vector double foo1 (vector double a)
+{
+   return vec_reve (a);
+}
+
+vector long long foo2 (vector long long a)
+{
+   return vec_reve (a);
+}
+
+/* { dg-final { scan-assembler-times {\mxxpermdi\M} 2 } } */
diff --git a/gcc/testsuite/gcc.target/powerpc/vec_reve_2.c b/gcc/testsuite/gcc.target/powerpc/vec_reve_2.c
new file mode 100644
index 00000000000..b6dd33d6d79
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/vec_reve_2.c
@@ -0,0 +1,28 @@
+/* { dg-require-effective-target powerpc_p9vector_ok } */
+/* { dg-options "-mdejagnu-cpu=power9 -O2 -maltivec" } */
+
+#include <altivec.h>
+
+vector int foo1 (vector int a)
+{
+   return vec_reve (a);
+}
+
+vector float foo2 (vector float a)
+{
+   return vec_reve (a);
+}
+
+vector short foo3 (vector short a)
+{
+   return vec_reve (a);
+}
+
+vector char foo4 (vector char a)
+{
+   return vec_reve (a);
+}
+
+/* { dg-final { scan-assembler-times {\mxxbrq\M} 4 } } */
+/* { dg-final { scan-assembler-times {\mxxbrw\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mxxbrh\M} 1 } } */