Index: /trunk/source/lib/misc.lisp
===================================================================
--- /trunk/source/lib/misc.lisp	(revision 13012)
+++ /trunk/source/lib/misc.lisp	(revision 13013)
@@ -1085,2 +1085,73 @@
 		area-watched area-watched)))
       
+;;; Return the effective address of a memory operand by using the
+;;; register state in xp, or NIL if we can't figure it out.
+;;; Needs to run inside a without-gcing form.
+(defun x86-memory-operand-ea (xp op)
+  (let* ((seg (x86::x86-memory-operand-seg op))
+	 (disp (x86::x86-memory-operand-disp op))
+	 (base (x86::x86-memory-operand-base op))
+	 (index (x86::x86-memory-operand-index op))
+	 (scale (x86::x86-memory-operand-scale op)))
+    (cond
+      ((and base index (not seg))
+       (let* ((base-re (x86::x86-register-operand-entry base))
+	      (index-re (x86::x86-register-operand-entry index))
+	      (base-num (x86::reg-entry-reg-num base-re))
+	      (index-num (x86::reg-entry-reg-num index-re))
+	      (base-val nil)
+	      (index-val nil))
+	 (when (logtest (x86::reg-entry-reg-flags base-re) x86::+regrex+)
+	   (incf base-num 8))
+	 (setq base-val (encoded-gpr-integer xp base-num))
+	 (when (logtest (x86::reg-entry-reg-flags index-re) x86::+regrex+)
+	   (incf index-num 8))
+	 (setq index-val (encoded-gpr-integer xp index-num))
+	 (when scale
+	   (setq index-val (ash index-val scale)))
+	 (+ (or disp 0) base-val index-val))))))
+
+;;; Try to emulate the disassembled instruction using the
+;;; register state in xp.  Return NIL if we couldn't do it.
+;;; This will run with other threads suspended.
+(defun x86-emulate-instruction (xp instruction)
+  (let* ((mnemonic (x86-di-mnemonic instruction))
+	 (op0 (x86-di-op0 instruction))
+	 (op1 (x86-di-op1 instruction))
+	 (op2 (x86-di-op2 instruction)))
+    (when (and op0 op1 (not op2)
+	       (typep op0 'x86::x86-register-operand)
+	       (typep op1 'x86::x86-memory-operand))
+      (without-gcing
+	(let* ((src-re (x86::x86-register-operand-entry op0))
+	       (src-num (x86::reg-entry-reg-num src-re))
+	       (src-val nil)
+	       (ea (x86-memory-operand-ea xp op1)))
+	  (when (logtest (x86::reg-entry-reg-flags src-re) x86::+regrex+)
+	    (incf src-num 8))
+	  (setq src-val (encoded-gpr-integer xp src-num))
+	  (when ea
+	    (with-macptrs ((p (%int-to-ptr ea)))
+	      (cond
+		((string= mnemonic "movb")
+		 (setf (%get-signed-byte p) (ldb (byte 8 0) src-val)))
+		((string= mnemonic "movw")
+		 (setf (%get-signed-word p) (ldb (byte 16 0) src-val)))
+		((string= mnemonic "movl")
+		 (setf (%get-signed-long p) (ldb (byte 32 0) src-val)))
+		((string= mnemonic "movq")
+		 (setf (%%get-signed-longlong p 0) (ldb (byte 64 0) src-val)))))))))))
+
+(defun x86-can-emulate-instruction (instruction)
+  (let* ((mnemonic (x86-di-mnemonic instruction))
+	 (op0 (x86-di-op0 instruction))
+	 (op1 (x86-di-op1 instruction))
+	 (op2 (x86-di-op2 instruction)))
+    (when (and op0 op1 (not op2)
+	       (typep op0 'x86::x86-register-operand)
+	       (typep op1 'x86::x86-memory-operand)
+	       (member mnemonic '("movb" "movw" "movl" "movq") :test 'string=))
+      (let* ((seg (x86::x86-memory-operand-seg op1))
+	     (base (x86::x86-memory-operand-base op1))
+	     (index (x86::x86-memory-operand-index op1)))
+	(and base index (not seg))))))