*** empty log message ***

From-SVN: r714

1 files changed, 17 insertions, 8 deletions

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 0770422..5d8027e 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -3464,8 +3464,7 @@
 	      (use (match_operand:SI 4 "immediate_operand" ""))
 	      (clobber (match_dup 1))
 	      (clobber (match_dup 2))
-	      (clobber (match_dup 3))
-	      (clobber (match_scratch:SI 5 ""))])]
+	      (clobber (match_dup 3))])]
   ""
   "
 {
@@ -3474,16 +3473,22 @@
   operands[3] = copy_to_mode_reg (SImode, operands[3]);
 }")
 
+;; memcmp recognizers.  The `cmpsb' opcode does nothing if the count is
+;; zero.  Emit extra code to make sure that a zero-length compare is EQ.
+
+;; ??? Most comparisons have a constant length, and it's therefore
+;; possible to know that the length is non-zero, and to avoid the extra
+;; code to handle zero-length compares.
+
 (define_insn ""
-  [(set (match_operand:QI 0 "general_operand" "=q")
+  [(set (match_operand:QI 0 "general_operand" "=&q")
 	(compare (mem:BLK (match_operand:SI 1 "general_operand" "S"))
 		 (mem:BLK (match_operand:SI 2 "general_operand" "D"))))
    (use (match_operand:SI 3 "general_operand" "c"))
    (use (match_operand:SI 4 "immediate_operand" "i"))
    (clobber (match_dup 1))
    (clobber (match_dup 2))
-   (clobber (match_dup 3))
-   (clobber (match_scratch:SI 5 "=&r"))]
+   (clobber (match_dup 3))]
   ""
   "*
 {
@@ -3515,12 +3520,16 @@
    (use (match_operand:SI 3 "immediate_operand" "i"))
    (clobber (match_dup 0))
    (clobber (match_dup 1))
-   (clobber (match_dup 2))
-   (clobber (match_scratch:SI 4 "=&r"))]
+   (clobber (match_dup 2))]
   ""
   "*
 {
-  output_asm_insn (AS2 (xor%L4,%4,%4), operands);
+  rtx xops[2];
+
+  xops[0] = gen_rtx (REG, QImode, 0);
+  xops[1] = CONST0_RTX (QImode);
+
+  output_asm_insn (AS2 (test%B0,%1,%0), xops);
   return \"repz\;cmps%B2\";
 }")