X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;ds=sidebyside;f=src%2Fcompiler%2Fx86%2Finsts.lisp;h=ce271e60722d2c36f79222076be11efb1e307108;hb=42ab0c5b87f834c69842713c60587a76f953411f;hp=05d9b338fc6a50fcd357b3352eb35322e01154b1;hpb=48ff891135e403e49037940bbad18d262e23df5e;p=sbcl.git

diff --git a/src/compiler/x86/insts.lisp b/src/compiler/x86/insts.lisp
index 05d9b33..ce271e6 100644
--- a/src/compiler/x86/insts.lisp
+++ b/src/compiler/x86/insts.lisp
@@ -896,6 +896,23 @@
      (emit-word segment value))
     (:dword
      (emit-dword segment value))))
+
+(defun toggle-word-width (chunk inst stream dstate)
+  (declare (ignore chunk inst stream))
+  (let ((word-width (or (sb!disassem:dstate-get-prop dstate 'word-width)
+                        +default-operand-size+)))
+    (setf (sb!disassem:dstate-get-prop dstate 'word-width)
+          (ecase word-width
+            (:word :dword)
+            (:dword :word)))))
+
+;;; This is a "prefix" instruction, which means that it modifies the
+;;; following instruction in some way without having an actual
+;;; mnemonic of its own.
+(define-instruction operand-size-prefix (segment)
+  (:printer byte ((op +operand-size-prefix-byte+))
+            nil                         ; don't actually print it
+            :control #'toggle-word-width))
 
 ;;;; general data transfer
 
@@ -1089,9 +1106,15 @@
 
 
 (define-instruction fs-segment-prefix (segment)
+  (:printer byte ((op #b01100100)))
   (:emitter
    (emit-byte segment #x64)))
 
+(define-instruction gs-segment-prefix (segment)
+  (:printer byte ((op #b01100101)))
+  (:emitter
+   (emit-byte segment #x65)))
+
 ;;;; flag control instructions
 
 ;;; CLC -- Clear Carry Flag.