builtins.c (builtin_memset_gen_str): New function.

2002-04-23  Roger Sayle  <roger@eyesopen.com>

	* builtins.c (builtin_memset_gen_str): New function.
	(expand_builtin_memset): Optimize the case of constant length, but
	unknown value.
testsuite:
	* gcc.c-torture/execute/string-opt-17.c: New test case.
	* gcc.c-torture/execute/memset-2.c: New test case.

From-SVN: r52662

1 files changed, 58 insertions, 1 deletions

diff --git a/gcc/builtins.c b/gcc/builtins.c
index a1ffe0a..84d47dd 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -126,6 +126,8 @@ static rtx expand_builtin_strncpy	PARAMS ((tree, rtx,
 						 enum machine_mode));
 static rtx builtin_memset_read_str	PARAMS ((PTR, HOST_WIDE_INT,
 						 enum machine_mode));
+static rtx builtin_memset_gen_str	PARAMS ((PTR, HOST_WIDE_INT,
+						 enum machine_mode));
 static rtx expand_builtin_memset	PARAMS ((tree, rtx,
                                                  enum machine_mode));
 static rtx expand_builtin_bzero		PARAMS ((tree));
@@ -2134,6 +2136,34 @@ builtin_memset_read_str (data, offset, mode)
   return c_readstr (p, mode);
 }
 
+/* Callback routine for store_by_pieces.  Return the RTL of a register
+   containing GET_MODE_SIZE (MODE) consecutive copies of the unsigned
+   char value given in the RTL register data.  For example, if mode is
+   4 bytes wide, return the RTL for 0x01010101*data.  */
+
+static rtx
+builtin_memset_gen_str (data, offset, mode)
+     PTR data;
+     HOST_WIDE_INT offset ATTRIBUTE_UNUSED;
+     enum machine_mode mode;
+{
+  rtx target, coeff;
+  size_t size;
+  char *p;
+
+  size = GET_MODE_SIZE (mode);
+  if (size==1)
+    return (rtx)data;
+
+  p = alloca (size);
+  memset (p, 1, size);
+  coeff = c_readstr (p, mode);
+
+  target = convert_to_mode (mode, (rtx)data, 1);
+  target = expand_mult (mode, target, coeff, NULL_RTX, 1);
+  return force_reg (mode, target);
+}
+
 /* Expand expression EXP, which is a call to the memset builtin.  Return 0
    if we failed the caller should emit a normal call, otherwise try to get
    the result in TARGET, if convenient (and in mode MODE if that's
@@ -2175,7 +2205,34 @@ expand_builtin_memset (exp, target, mode)
         }
 
       if (TREE_CODE (val) != INTEGER_CST)
-	return 0;
+        {
+          rtx val_rtx;
+
+          if (!host_integerp (len, 1))
+            return 0;
+
+          if (optimize_size && tree_low_cst (len, 1) > 1)
+            return 0;
+
+          /* Assume that we can memset by pieces if we can store the
+           * the coefficients by pieces (in the required modes).
+           * We can't pass builtin_memset_gen_str as that emits RTL.  */
+          c = 1;
+	  if (!can_store_by_pieces (tree_low_cst (len, 1),
+				    builtin_memset_read_str,
+                                    (PTR) &c, dest_align))
+	    return 0;
+
+          val = fold (build1 (CONVERT_EXPR, unsigned_char_type_node, val));
+          val_rtx = expand_expr (val, NULL_RTX, VOIDmode, 0);
+          val_rtx = force_reg (TYPE_MODE (unsigned_char_type_node),
+                               val_rtx);
+	  dest_mem = get_memory_rtx (dest);
+	  store_by_pieces (dest_mem, tree_low_cst (len, 1),
+			   builtin_memset_gen_str,
+			   (PTR)val_rtx, dest_align);
+	  return force_operand (XEXP (dest_mem, 0), NULL_RTX);
+        }
 
       if (target_char_cast (val, &c))
 	return 0;