From 5be0b846b1ca0131fc6c67c1ff7dcf64791ebc73 Mon Sep 17 00:00:00 2001
From: Nilay Vaish <nilay@cs.wisc.edu>
Date: Mon, 27 Jan 2014 18:50:52 -0600
Subject: x86: implements fxch instruction.

---
 src/arch/x86/isa/decoder/x87.isa                        | 12 +++++++++---
 .../insts/x87/data_transfer_and_conversion/exchange.py  | 17 ++++++++++++++++-
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/arch/x86/isa/decoder/x87.isa b/src/arch/x86/isa/decoder/x87.isa
index ac1306412..61f125e7c 100644
--- a/src/arch/x86/isa/decoder/x87.isa
+++ b/src/arch/x86/isa/decoder/x87.isa
@@ -59,7 +59,7 @@ format WarnUnimpl {
                 default: Inst::FLD(Md);
             }
             0x1: decode MODRM_MOD {
-                0x3: fxch();
+                0x3: Inst::FXCH(Eq);
                 default: Inst::UD2();
             }
             0x2: decode MODRM_MOD {
@@ -240,8 +240,14 @@ format WarnUnimpl {
                 0x3: Inst::UD2();
                 default: fisttp();
             }
-            0x2: Inst::FST(Eq);
-            0x3: Inst::FSTP(Eq);
+            0x2: decode MODRM_MOD {
+                0x3: Inst::FST(Eq);
+                default: Inst::FST(Mq);
+            }
+            0x3: decode MODRM_MOD {
+                0x3: Inst::FSTP(Eq);
+                default: Inst::FSTP(Mq);
+            }
             0x4: decode MODRM_MOD {
                 0x3: fucom();
                 default: frstor();
diff --git a/src/arch/x86/isa/insts/x87/data_transfer_and_conversion/exchange.py b/src/arch/x86/isa/insts/x87/data_transfer_and_conversion/exchange.py
index 982ac8e55..b6fbb01cc 100644
--- a/src/arch/x86/isa/insts/x87/data_transfer_and_conversion/exchange.py
+++ b/src/arch/x86/isa/insts/x87/data_transfer_and_conversion/exchange.py
@@ -36,5 +36,20 @@
 # Authors: Gabe Black
 
 microcode = '''
-# FXCH
+def macroop FXCH_R
+{
+    movfp ufp1, sti
+    movfp sti, st(0)
+    movfp st(0), ufp1
+};
+
+def macroop FXCH_M
+{
+    fault "new UnimpInstFault"
+};
+
+def macroop FXCH_P
+{
+   fault "new UnimpInstFault"
+};
 '''
-- 
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