From: Stas Boukarev <stassats@gmail.com>
Date: Mon, 9 Sep 2013 15:54:05 +0000 (+0400)
Subject: Micro-optimize move-immediate on x86-64.
X-Git-Url: http://repo.macrolet.net/gitweb/?a=commitdiff_plain;h=17ba9560a86774392eed4e94896115865efafe13;p=sbcl.git

Micro-optimize move-immediate on x86-64.

Use XOR X, X when the immediate is 0.
---

diff --git a/src/compiler/x86-64/move.lisp b/src/compiler/x86-64/move.lisp
index dbf58ed..f10a953 100644
--- a/src/compiler/x86-64/move.lisp
+++ b/src/compiler/x86-64/move.lisp
@@ -103,9 +103,7 @@
         (let ((val (tn-value x)))
           (etypecase val
             (integer
-             (if (and (zerop val) (sc-is y any-reg descriptor-reg))
-                 (zeroize y)
-                 (move-immediate y (fixnumize val) temp)))
+             (move-immediate y (fixnumize val) temp))
             (symbol
              (inst mov y (+ nil-value (static-symbol-offset val))))
             (character
@@ -127,7 +125,9 @@
     ;; If target is a register, we can just mov it there directly
     ((and (tn-p target)
           (sc-is target signed-reg unsigned-reg descriptor-reg any-reg))
-     (inst mov target val))
+     (if (zerop val)
+         (zeroize target)
+         (inst mov target val)))
     ;; Likewise if the value is small enough.
     ((typep val '(signed-byte 32))
      (inst mov target val))
diff --git a/src/compiler/x86-64/static-fn.lisp b/src/compiler/x86-64/static-fn.lisp
index ec4809a..1f0c370 100644
--- a/src/compiler/x86-64/static-fn.lisp
+++ b/src/compiler/x86-64/static-fn.lisp
@@ -91,7 +91,7 @@
                 (inst enter n-word-bytes)))
 
          ,(if (zerop num-args)
-              '(inst xor ecx ecx)
+              '(zeroize ecx)
               `(inst mov ecx ,(fixnumize num-args)))
 
          (note-this-location vop :call-site)