[SVE] PR96463 - Optimise svld1rq from vectors

[Prathamesh Kulkarni via Gcc-patches]

Hi Richard,
I have attached a WIP untested patch for PR96463.
IIUC, the PR suggests to transform
lhs = svld1rq ({-1, -1, ...}, &v[0])
into:
lhs = vec_perm_expr<v, v, {0, 0, ...}>
if v is vector of 4 elements, and each element is 32 bits on little
endian target ?

I am sorry if this sounds like a silly question, but I am not sure how
to convert a vector of type int32x4_t into svint32_t ? In the patch, I
simply used NOP_EXPR (which I expected to fail), and gave type error
during gimple verification:

svint32_t
foo (int32x4_t x)
{
  return svld1rq (svptrue_b8 (), &x[0]);
}

transformed to:
EMERGENCY DUMP:

svint32_t foo (int32x4_t x)
{
  svint32_t _3;
  __Int32x4_t _4;

  <bb 2> :
  _4 = VEC_PERM_EXPR <x_5(D), x_5(D), { 0, 0, 0, 0 }>;
  _3 = (svint32_t) _4;
  return _3;

}

and ICE's with:
pr96463.c:8:1: error: invalid vector types in nop conversion
    8 | }
      | ^
svint32_t
__Int32x4_t
_3 = (svint32_t) _4;
during GIMPLE pass: ccp

Could you please suggest how to proceed ?

Thanks,
Prathamesh

diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc 
b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
index 02e42a71e5e..3834f33443a 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
@@ -44,6 +44,13 @@
 #include "aarch64-sve-builtins-shapes.h"
 #include "aarch64-sve-builtins-base.h"
 #include "aarch64-sve-builtins-functions.h"
+#include "print-tree.h"
+#include "gimple-pretty-print.h"
+
+/* ??? Including tree-ssanames.h requires including other header dependencies.
+       Just including the prototype for now.  */
+extern tree make_ssa_name_fn (struct function *, tree, gimple *,
+                             unsigned int version = 0);
 
 using namespace aarch64_sve;
 
@@ -1207,6 +1214,52 @@ public:
     insn_code icode = code_for_aarch64_sve_ld1rq (e.vector_mode (0));
     return e.use_contiguous_load_insn (icode);
   }
+
+  gimple *
+  fold (gimple_folder &f) const OVERRIDE
+  {
+    tree arg0 = gimple_call_arg (f.call, 0);
+    tree arg1 = gimple_call_arg (f.call, 1);
+
+    /* Transform:
+       lhs = svld1rq ({-1, -1, ... }, &v[0])
+       into:
+       tmp = vec_perm_expr<v, v, {0, 0, ...}>.
+       lhs = nop_expr tmp
+       on little endian target.  */
+
+    if (!BYTES_BIG_ENDIAN
+       && integer_all_onesp (arg0)
+       && TREE_CODE (arg1) == ADDR_EXPR)
+      {
+       tree t = TREE_OPERAND (arg1, 0);
+       if (TREE_CODE (t) == ARRAY_REF)
+         {
+           tree index = TREE_OPERAND (t, 1);
+           t = TREE_OPERAND (t, 0);
+           if (integer_zerop (index) && TREE_CODE (t) == VIEW_CONVERT_EXPR)
+             {
+               t = TREE_OPERAND (t, 0);
+               tree vectype = TREE_TYPE (t);
+               if (VECTOR_TYPE_P (vectype)
+                   && known_eq (TYPE_VECTOR_SUBPARTS (vectype), 4u)
+                   && wi::to_wide (TYPE_SIZE (vectype)) == 128)
+                 {
+                   tree new_temp = ::make_ssa_name_fn (cfun, vectype, NULL);
+                   tree zero_vec = build_vector_from_val (vectype, index);
+                   gimple *g = gimple_build_assign (new_temp, VEC_PERM_EXPR, 
t, t, zero_vec);
+                   /* ??? How to convert between vector types if 
gimple_call_lhs (f.call) and
+                          new_temp have different types ?  */
+                   gimple *g2 = gimple_build_assign (gimple_call_lhs (f.call), 
NOP_EXPR, new_temp);
+                   gsi_insert_before (f.gsi, g, GSI_SAME_STMT);
+                   return g2;
+                 }
+             }
+         }
+      }
+
+    return NULL;
+  }
 };
 
 class svld1ro_impl : public load_replicate