[SVE] Fold svdupq to VEC_PERM_EXPR if elements are not constant

[Prathamesh Kulkarni via Gcc-patches]

Hi Richard,
Sorry I forgot to commit this patch, which you had approved in:
https://gcc.gnu.org/pipermail/gcc-patches/2023-April/615308.html

Just for context for the following test:
svint32_t f_s32(int32x4_t x)
{
  return svdupq_s32 (x[0], x[1], x[2], x[3]);
}

-O3 -mcpu=generic+sve generates following code after interleave+zip1 patch:
f_s32:
        dup     s31, v0.s[1]
        mov     v30.8b, v0.8b
        ins     v31.s[1], v0.s[3]
        ins     v30.s[1], v0.s[2]
        zip1    v0.4s, v30.4s, v31.4s
        dup     z0.q, z0.q[0]
        ret

Code-gen with attached patch:
f_s32:
        dup     z0.q, z0.q[0]
        ret

Bootstrapped+tested on aarch64-linux-gnu.
OK to commit ?

Thanks,
Prathamesh

[SVE] Fold svdupq to VEC_PERM_EXPR if elements are not constant.

gcc/ChangeLog:
        * config/aarch64/aarch64-sve-builtins-base.cc
        (svdupq_impl::fold_nonconst_dupq): New method.
        (svdupq_impl::fold): Call fold_nonconst_dupq.

gcc/testsuite/ChangeLog:
        * gcc.target/aarch64/sve/acle/general/dupq_11.c: New test.

diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc 
b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
index 95b4cb8a943..9010ecca6da 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
@@ -817,6 +817,52 @@ public:
 
 class svdupq_impl : public quiet<function_base>
 {
+private:
+  gimple *
+  fold_nonconst_dupq (gimple_folder &f) const
+  {
+    /* Lower lhs = svdupq (arg0, arg1, ..., argN} into:
+       tmp = {arg0, arg1, ..., arg<N-1>}
+       lhs = VEC_PERM_EXPR (tmp, tmp, {0, 1, 2, N-1, ...})  */
+
+    if (f.type_suffix (0).bool_p
+       || BYTES_BIG_ENDIAN)
+      return NULL;
+
+    tree lhs = gimple_call_lhs (f.call);
+    tree lhs_type = TREE_TYPE (lhs);
+    tree elt_type = TREE_TYPE (lhs_type);
+    scalar_mode elt_mode = SCALAR_TYPE_MODE (elt_type);
+    machine_mode vq_mode = aarch64_vq_mode (elt_mode).require ();
+    tree vq_type = build_vector_type_for_mode (elt_type, vq_mode);
+
+    unsigned nargs = gimple_call_num_args (f.call);
+    vec<constructor_elt, va_gc> *v;
+    vec_alloc (v, nargs);
+    for (unsigned i = 0; i < nargs; i++)
+      CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, gimple_call_arg (f.call, i));
+    tree vec = build_constructor (vq_type, v);
+    tree tmp = make_ssa_name_fn (cfun, vq_type, 0);
+    gimple *g = gimple_build_assign (tmp, vec);
+
+    gimple_seq stmts = NULL;
+    gimple_seq_add_stmt_without_update (&stmts, g);
+
+    poly_uint64 lhs_len = TYPE_VECTOR_SUBPARTS (lhs_type);
+    vec_perm_builder sel (lhs_len, nargs, 1);
+    for (unsigned i = 0; i < nargs; i++)
+      sel.quick_push (i);
+
+    vec_perm_indices indices (sel, 1, nargs);
+    tree mask_type = build_vector_type (ssizetype, lhs_len);
+    tree mask = vec_perm_indices_to_tree (mask_type, indices);
+
+    gimple *g2 = gimple_build_assign (lhs, VEC_PERM_EXPR, tmp, tmp, mask);
+    gimple_seq_add_stmt_without_update (&stmts, g2);
+    gsi_replace_with_seq (f.gsi, stmts, false);
+    return g2;
+  }
+
 public:
   gimple *
   fold (gimple_folder &f) const override
@@ -832,7 +878,7 @@ public:
       {
        tree elt = gimple_call_arg (f.call, i);
        if (!CONSTANT_CLASS_P (elt))
-         return NULL;
+         return fold_nonconst_dupq (f);
        builder.quick_push (elt);
        for (unsigned int j = 1; j < factor; ++j)
          builder.quick_push (build_zero_cst (TREE_TYPE (vec_type)));
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/dupq_11.c 
b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/dupq_11.c
new file mode 100644
index 00000000000..f19f8deb1e5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/dupq_11.c
@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+
+#include <arm_sve.h>
+#include <arm_neon.h>
+
+svint8_t f_s8(int8x16_t x)
+{
+  return svdupq_s8 (x[0], x[1], x[2], x[3], x[4], x[5], x[6], x[7],
+                   x[8], x[9], x[10], x[11], x[12], x[13], x[14], x[15]);
+}
+
+svint16_t f_s16(int16x8_t x)
+{
+  return svdupq_s16 (x[0], x[1], x[2], x[3], x[4], x[5], x[6], x[7]);
+}
+
+svint32_t f_s32(int32x4_t x)
+{
+  return svdupq_s32 (x[0], x[1], x[2], x[3]);
+}
+
+svint64_t f_s64(int64x2_t x)
+{
+  return svdupq_s64 (x[0], x[1]);
+}
+
+/* { dg-final { scan-tree-dump "VEC_PERM_EXPR" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "svdupq" "optimized" } } */
+
+/* { dg-final { scan-assembler-times {\tdup\tz[0-9]+\.q, z[0-9]+\.q\[0\]\n} 4 
} } */