[PATCH PR94442] [AArch64] Redundant ldp/stp instructions emitted at -O3

[xiezhiheng <xiezhiheng@huawei.com>]

Hi,

This is a fix for pr94442.
I modify get_inner_reference to handle the case for MEM[ptr, off].
I extract the "off" and add it to the recorded offset, then I build a
MEM[ptr, 0] and return it later.

diff --git a/gcc/expr.c b/gcc/expr.c
index 3c68b0d754c..8cc18449a0c 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -7362,7 +7362,8 @@ tree
 get_inner_reference (tree exp, poly_int64_pod *pbitsize,
 		     poly_int64_pod *pbitpos, tree *poffset,
 		     machine_mode *pmode, int *punsignedp,
-		     int *preversep, int *pvolatilep)
+		     int *preversep, int *pvolatilep,
+		     bool include_memref_p)
 {
   tree size_tree = 0;
   machine_mode mode = VOIDmode;
@@ -7509,6 +7510,21 @@ get_inner_reference (tree exp, poly_int64_pod *pbitsize,
 		}
 	      exp = TREE_OPERAND (TREE_OPERAND (exp, 0), 0);
 	    }
+	  else if (include_memref_p
+		   && TREE_CODE (TREE_OPERAND (exp, 0)) == SSA_NAME)
+	    {
+	      tree off = TREE_OPERAND (exp, 1);
+	      if (!integer_zerop (off))
+		{
+		  poly_offset_int boff = mem_ref_offset (exp);
+		  boff <<= LOG2_BITS_PER_UNIT;
+		  bit_offset += boff;
+
+		  exp = build2 (MEM_REF, TREE_TYPE (exp),
+				TREE_OPERAND (exp, 0),
+				build_int_cst (TREE_TYPE (off), 0));
+		}
+	    }
 	  goto done;
 
 	default:
@@ -10786,7 +10802,7 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
 	int reversep, volatilep = 0, must_force_mem;
 	tree tem
 	  = get_inner_reference (exp, &bitsize, &bitpos, &offset, &mode1,
-				 &unsignedp, &reversep, &volatilep);
+				 &unsignedp, &reversep, &volatilep, true);
 	rtx orig_op0, memloc;
 	bool clear_mem_expr = false;
 
diff --git a/gcc/tree.h b/gcc/tree.h
index a74872f5f3e..7df0d15f7f9 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -6139,7 +6139,8 @@ extern bool complete_ctor_at_level_p (const_tree, HOST_WIDE_INT, const_tree);
    look for the ultimate containing object, which is returned and specify
    the access position and size.  */
 extern tree get_inner_reference (tree, poly_int64_pod *, poly_int64_pod *,
-				 tree *, machine_mode *, int *, int *, int *);
+				 tree *, machine_mode *, int *, int *, int *,
+				 bool = false);
 
 extern tree build_personality_function (const char *);


I add an argument "include_memref_p" to control whether to go into MEM_REF,
because without it will cause the test case "Warray-bounds-46.c" to fail in regression.

It because function set_base_and_offset in gimple-ssa-warn-restrict.c
  base = get_inner_reference (expr, &bitsize, &bitpos, &var_off,
                              &mode, &sign, &reverse, &vol);
  ...
  ...
  if (TREE_CODE (base) == MEM_REF)
    {
      tree memrefoff = fold_convert (ptrdiff_type_node, TREE_OPERAND (base, 1));
      extend_offset_range (memrefoff);
      base = TREE_OPERAND (base, 0);

      if (refoff != HOST_WIDE_INT_MIN
          && TREE_CODE (expr) == COMPONENT_REF)
        {
          /* Bump up the offset of the referenced subobject to reflect
             the offset to the enclosing object.  For example, so that
             in
               struct S { char a, b[3]; } s[2];
               strcpy (s[1].b, "1234");
             REFOFF is set to s[1].b - (char*)s.  */
          offset_int off = tree_to_shwi (memrefoff);
          refoff += off;
        }

      if (!integer_zerop (memrefoff))       <=================
        /* A non-zero offset into an array of struct with flexible array
           members implies that the array is empty because there is no
           way to initialize such a member when it belongs to an array.
           This must be some sort of a bug.  */
        refsize = 0;
    }

needs MEM_REF offset to judge whether refsize should be set to zero.
But I fold the offset into bitpos and the offset will always be zero.

Suggestion?