(expand_builtin, case BUILTIN_MEMSET): Open code memset where val == 0.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@12363 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/expr.c b/gcc/expr.c
index 1603b62..5dd6700 100644 (file)
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -8531,6 +8531,58 @@ expand_builtin (exp, target, subtarget, mode, ignore)
          return force_operand (dest_rtx, NULL_RTX);
        }
 
+    case BUILT_IN_MEMSET:
+      /* If not optimizing, call the library function.  */
+      if (!optimize && ! CALLED_AS_BUILT_IN (fndecl))
+       break;
+
+      if (arglist == 0
+         /* Arg could be non-pointer if user redeclared this fcn wrong.  */
+         || TREE_CODE (TREE_TYPE (TREE_VALUE (arglist))) != POINTER_TYPE
+         || TREE_CHAIN (arglist) == 0
+         || (TREE_CODE (TREE_TYPE (TREE_VALUE (TREE_CHAIN (arglist))))
+             != INTEGER_TYPE)
+         || TREE_CHAIN (TREE_CHAIN (arglist)) == 0
+         || (INTEGER_CST
+             != (TREE_CODE (TREE_TYPE
+                            (TREE_VALUE
+                             (TREE_CHAIN (TREE_CHAIN (arglist))))))))
+       break;
+      else
+       {
+         tree dest = TREE_VALUE (arglist);
+         tree val = TREE_VALUE (TREE_CHAIN (arglist));
+         tree len = TREE_VALUE (TREE_CHAIN (TREE_CHAIN (arglist)));
+         tree type;
+
+         int dest_align
+           = get_pointer_alignment (dest, BIGGEST_ALIGNMENT) / BITS_PER_UNIT;
+         rtx dest_rtx, dest_mem;
+
+         /* If DEST is not a pointer type, don't do this 
+            operation in-line.  */
+         if (dest_align == 0)
+           break;
+
+         /* If VAL is not 0, don't do this operation in-line. */
+         if (expand_expr (val, NULL_RTX, VOIDmode, 0) != const0_rtx)
+           break;
+
+         dest_rtx = expand_expr (dest, NULL_RTX, ptr_mode, EXPAND_SUM);
+         dest_mem = gen_rtx (MEM, BLKmode,
+                             memory_address (BLKmode, dest_rtx));
+         /* There could be a void* cast on top of the object.  */
+         while (TREE_CODE (dest) == NOP_EXPR)
+           dest = TREE_OPERAND (dest, 0);
+         type = TREE_TYPE (TREE_TYPE (dest));
+         MEM_IN_STRUCT_P (dest_mem) = AGGREGATE_TYPE_P (type);
+
+         clear_storage (dest_mem, expand_expr (len, NULL_RTX, VOIDmode, 0),
+                           dest_align);
+
+         return force_operand (dest_rtx, NULL_RTX);
+       }
+
 /* These comparison functions need an instruction that returns an actual
    index.  An ordinary compare that just sets the condition codes
    is not enough.  */