Make the predecoder an object with it's own switched header file. Start adding predecoding functionality to x86.

src/arch/SConscript:
src/arch/alpha/utility.hh:
src/arch/mips/utility.hh:
src/arch/sparc/utility.hh:
src/cpu/base.hh:
src/cpu/o3/fetch.hh:
src/cpu/o3/fetch_impl.hh:
src/cpu/simple/atomic.cc:
src/cpu/simple/base.cc:
src/cpu/simple/base.hh:
src/cpu/static_inst.hh:
src/arch/alpha/predecoder.hh:
src/arch/mips/predecoder.hh:
src/arch/sparc/predecoder.hh:
    Make the predecoder an object with it's own switched header file.

--HG--
extra : convert_revision : 77206e29089130e86b97164c30022a062699ba86

6 files changed, 625 insertions, 15 deletions

diff --git a/src/arch/x86/SConscript b/src/arch/x86/SConscript
index fff29ba89..8be59e0c0 100644
--- a/src/arch/x86/SConscript
+++ b/src/arch/x86/SConscript
@@ -103,6 +103,7 @@ base_sources = Split('''
 	miscregfile.cc
 	regfile.cc
 	remote_gdb.cc
+	predecoder_tables.cc
 	''')
 
 # Full-system sources
diff --git a/src/arch/x86/isa/formats/unknown.isa b/src/arch/x86/isa/formats/unknown.isa
index 605ddcb69..43ddc20c1 100644
--- a/src/arch/x86/isa/formats/unknown.isa
+++ b/src/arch/x86/isa/formats/unknown.isa
@@ -120,7 +120,8 @@ output exec {{
         Fault Unknown::execute(%(CPU_exec_context)s *xc,
                 Trace::InstRecord *traceData) const
         {
-            panic("No instructions are implemented for X86!\n");
+            warn("No instructions are implemented for X86!\n");
+            return NoFault;
         }
 }};
 
diff --git a/src/arch/x86/predecoder.hh b/src/arch/x86/predecoder.hh
new file mode 100644
index 000000000..371ce9db9
--- /dev/null
+++ b/src/arch/x86/predecoder.hh
@@ -0,0 +1,412 @@
+/*
+ * Copyright (c) 2007 The Hewlett-Packard Development Company
+ * All rights reserved.
+ *
+ * Redistribution and use of this software in source and binary forms,
+ * with or without modification, are permitted provided that the
+ * following conditions are met:
+ *
+ * The software must be used only for Non-Commercial Use which means any
+ * use which is NOT directed to receiving any direct monetary
+ * compensation for, or commercial advantage from such use.  Illustrative
+ * examples of non-commercial use are academic research, personal study,
+ * teaching, education and corporate research & development.
+ * Illustrative examples of commercial use are distributing products for
+ * commercial advantage and providing services using the software for
+ * commercial advantage.
+ *
+ * If you wish to use this software or functionality therein that may be
+ * covered by patents for commercial use, please contact:
+ *     Director of Intellectual Property Licensing
+ *     Office of Strategy and Technology
+ *     Hewlett-Packard Company
+ *     1501 Page Mill Road
+ *     Palo Alto, California  94304
+ *
+ * Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.  Redistributions
+ * in binary form must reproduce the above copyright notice, this list of
+ * conditions and the following disclaimer in the documentation and/or
+ * other materials provided with the distribution.  Neither the name of
+ * the COPYRIGHT HOLDER(s), HEWLETT-PACKARD COMPANY, nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.  No right of
+ * sublicense is granted herewith.  Derivatives of the software and
+ * output created using the software may be prepared, but only for
+ * Non-Commercial Uses.  Derivatives of the software may be shared with
+ * others provided: (i) the others agree to abide by the list of
+ * conditions herein which includes the Non-Commercial Use restrictions;
+ * and (ii) such Derivatives of the software include the above copyright
+ * notice to acknowledge the contribution from this software where
+ * applicable, this list of conditions and the disclaimer below.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Gabe Black
+ */
+
+#ifndef __ARCH_X86_PREDECODER_HH__
+#define __ARCH_X86_PREDECODER_HH__
+
+#include "arch/x86/types.hh"
+#include "base/bitfield.hh"
+#include "base/misc.hh"
+#include "sim/host.hh"
+
+class ThreadContext;
+
+namespace X86ISA
+{
+    class Predecoder
+    {
+      private:
+        static const uint8_t Prefixes[256];
+        static const uint8_t UsesModRM[2][256];
+
+      protected:
+        ThreadContext * tc;
+        //The bytes to be predecoded
+        MachInst fetchChunk;
+        //The pc of the start of fetchChunk
+        Addr basePC;
+        //The offset into fetchChunk of current processing
+        int offset;
+        //The extended machine instruction being generated
+        ExtMachInst emi;
+
+        //State machine state
+      protected:
+        //Whether or not we're out of bytes
+        bool outOfBytes;
+        //Whether we've completed generating an ExtMachInst
+        bool emiIsReady;
+        //The size of the displacement value
+        int displacementSize;
+        int displacementCollected;
+        //The size of the immediate value
+        int immediateSize;
+        int immediateCollected;
+
+        //These are local to some of the states. I need to turn the states
+        //into inline functions to clean things up a bit.
+        int toGet;
+        int remaining;
+        MachInst partialDisp;
+
+        enum State {
+            Prefix,
+            Opcode,
+            ModRM,
+            SIB,
+            Displacement,
+            Immediate
+        };
+
+        State state;
+
+      public:
+        Predecoder(ThreadContext * _tc) :
+            tc(_tc), basePC(0), offset(0),
+            outOfBytes(true), emiIsReady(false),
+            state(Prefix)
+        {}
+
+        ThreadContext * getTC()
+        {
+            return tc;
+        }
+
+        void setTC(ThreadContext * _tc)
+        {
+            tc = _tc;
+        }
+
+        void process()
+        {
+            warn("About to process some bytes\n");
+            assert(!outOfBytes);
+            assert(!emiIsReady);
+            while(!emiIsReady && !outOfBytes)
+            {
+                uint8_t nextByte = (fetchChunk >> (offset * 8)) & 0xff;
+                switch(state)
+                {
+                  case Prefix:
+                    uint8_t prefix = Prefixes[nextByte];
+                    switch(prefix)
+                    {
+                        //Operand size override prefixes
+                      case OperandSizeOverride:
+                        warn("Found operand size override prefix!\n");
+                        offset++;
+                        break;
+                      case AddressSizeOverride:
+                        warn("Found address size override prefix!\n");
+                        offset++;
+                        break;
+                        //Segment override prefixes
+                      case CSOverride:
+                        warn("Found cs segment override!\n");
+                        offset++;
+                        break;
+                      case DSOverride:
+                        warn("Found ds segment override!\n");
+                        offset++;
+                        break;
+                      case ESOverride:
+                        warn("Found es segment override!\n");
+                        offset++;
+                        break;
+                      case FSOverride:
+                        warn("Found fs segment override!\n");
+                        offset++;
+                        break;
+                      case GSOverride:
+                        warn("Found gs segment override!\n");
+                        offset++;
+                        break;
+                      case SSOverride:
+                        warn("Found ss segment override!\n");
+                        offset++;
+                        break;
+                      case Lock:
+                        warn("Found lock prefix!\n");
+                        offset++;
+                        break;
+                      case Rep:
+                        warn("Found rep prefix!\n");
+                        offset++;
+                        break;
+                      case Repne:
+                        warn("Found repne prefix!\n");
+                        offset++;
+                        break;
+                      case Rex:
+                        warn("Found Rex prefix %#x!\n", nextByte);
+                        offset++;
+                        break;
+                      case 0:
+                        emi.twoByteOpcode = false;
+                        state = Opcode;
+                        break;
+                      default:
+                        panic("Unrecognized prefix %#x\n", nextByte);
+                    }
+                    break;
+                  case Opcode:
+                    if(nextByte == 0xf0)
+                    {
+                        warn("Found two byte opcode!\n");
+                        emi.twoByteOpcode = true;
+                    }
+                    else
+                    {
+                        warn("Found opcode %#x!\n", nextByte);
+                        if (UsesModRM[emi.twoByteOpcode ? 1 : 0][nextByte]) {
+                            state = ModRM;
+                        } else if(0 /* uses immediate */) {
+                            //Figure out how big the immediate should be
+                            immediateCollected = 0;
+                            emi.immediate = 0;
+                            state = Immediate;
+                        } else {
+                            emiIsReady = true;
+                            state = Prefix;
+                        }
+                    }
+                    offset++;
+                    break;
+                  case ModRM:
+                    warn("Found modrm byte %#x!\n", nextByte);
+                    if (0) {//in 16 bit mode
+                        //figure out 16 bit displacement size
+                        if(nextByte & 0xC7 == 0x06 ||
+                                nextByte & 0xC0 == 0x40)
+                            displacementSize = 1;
+                        else if(nextByte & 0xC7 == 0x80)
+                            displacementSize = 2;
+                        else
+                            displacementSize = 0;
+                    } else {
+                        //figure out 32/64 bit displacement size
+                        if(nextByte & 0xC7 == 0x06 ||
+                                nextByte & 0xC0 == 0x40)
+                            displacementSize = 4;
+                        else if(nextByte & 0xC7 == 0x80)
+                            displacementSize = 2;
+                        else
+                            displacementSize = 4;
+                    }
+                    //If there's an SIB, get that next.
+                    //There is no SIB in 16 bit mode.
+                    if(nextByte & 0x7 == 4 &&
+                            nextByte & 0xC0 != 0xC0) {
+                            // && in 32/64 bit mode)
+                        state = SIB;
+                    } else if(displacementSize) {
+                        displacementCollected = 0;
+                        emi.displacement = 0;
+                        state = Displacement;
+                    } else if(immediateSize) {
+                        immediateCollected = 0;
+                        emi.immediate = 0;
+                        state = Immediate;
+                    } else {
+                        emiIsReady = true;
+                        state = Prefix;
+                    }
+                    //The ModRM byte is consumed no matter what
+                    offset++;
+                    break;
+                  case SIB:
+                    warn("Found SIB byte %#x!\n", nextByte);
+                    offset++;
+                    if(displacementSize) {
+                        displacementCollected = 0;
+                        emi.displacement = 0;
+                        state = Displacement;
+                    } else if(immediateSize) {
+                        immediateCollected = 0;
+                        emi.immediate = 0;
+                        state = Immediate;
+                    } else {
+                        emiIsReady = true;
+                        state = Prefix;
+                    }
+                    break;
+                  case Displacement:
+                    //Gather up the displacement, or at least as much of it
+                    //as we can get.
+
+                    //Figure out how many bytes we still need to get for the
+                    //displacement.
+                    toGet = displacementSize - displacementCollected;
+                    //Figure out how many bytes are left in our "buffer"
+                    remaining = sizeof(MachInst) - offset;
+                    //Get as much as we need, up to the amount available.
+                    toGet = toGet > remaining ? remaining : toGet;
+
+                    //Shift the bytes we want to be all the way to the right
+                    partialDisp = fetchChunk >> offset;
+                    //Mask off what we don't want
+                    partialDisp &= mask(toGet * 8);
+                    //Shift it over to overlay with our displacement.
+                    partialDisp <<= displacementCollected;
+                    //Put it into our displacement
+                    emi.displacement |= partialDisp;
+                    //Update how many bytes we've collected.
+                    displacementCollected += toGet;
+
+                    if(displacementSize == displacementCollected) {
+                        //Sign extend the displacement
+                        switch(displacementSize)
+                        {
+                          case 1:
+                            emi.displacement = sext<8>(emi.displacement);
+                            break;
+                          case 2:
+                            emi.displacement = sext<16>(emi.displacement);
+                            break;
+                          case 4:
+                            emi.displacement = sext<32>(emi.displacement);
+                            break;
+                          default:
+                            panic("Undefined displacement size!\n");
+                        }
+                        if(immediateSize) {
+                            immediateCollected = 0;
+                            emi.immediate = 0;
+                            state = Immediate;
+                        } else {
+                            emiIsReady = true;
+                            state = Prefix;
+                        }
+                    }
+                    break;
+                  case Immediate:
+                    //Gather up the displacement, or at least as much of it
+                    //as we can get
+
+                    //Figure out how many bytes we still need to get for the
+                    //immediate.
+                    toGet = immediateSize - immediateCollected;
+                    //Figure out how many bytes are left in our "buffer"
+                    remaining = sizeof(MachInst) - offset;
+                    //Get as much as we need, up to the amount available.
+                    toGet = toGet > remaining ? remaining : toGet;
+
+                    //Shift the bytes we want to be all the way to the right
+                    partialDisp = fetchChunk >> offset;
+                    //Mask off what we don't want
+                    partialDisp &= mask(toGet * 8);
+                    //Shift it over to overlay with our immediate.
+                    partialDisp <<= displacementCollected;
+                    //Put it into our immediate
+                    emi.displacement |= partialDisp;
+                    //Update how many bytes we've collected.
+                    displacementCollected += toGet;
+                    if(immediateSize == immediateCollected)
+                    {
+                        emiIsReady = true;
+                        state = Prefix;
+                    }
+                    break;
+                  default:
+                    panic("Unrecognized state! %d\n", state);
+                }
+                if(offset == sizeof(MachInst))
+                    outOfBytes = true;
+            }
+        }
+
+        //Use this to give data to the predecoder. This should be used
+        //when there is control flow.
+        void moreBytes(Addr currPC, Addr off, MachInst data)
+        {
+            basePC = currPC;
+            offset = off;
+            fetchChunk = data;
+            assert(off < sizeof(MachInst));
+            outOfBytes = false;
+            warn("About to call process.\n");
+            process();
+        }
+
+        //Use this to give data to the predecoder. This should be used
+        //when instructions are executed in order.
+        void moreBytes(MachInst machInst)
+        {
+            moreBytes(basePC + sizeof(machInst), 0, machInst);
+        }
+
+        bool needMoreBytes()
+        {
+            return outOfBytes;
+        }
+
+        bool extMachInstReady()
+        {
+            return emiIsReady;
+        }
+
+        //This returns a constant reference to the ExtMachInst to avoid a copy
+        const ExtMachInst & getExtMachInst()
+        {
+            assert(emiIsReady);
+            emiIsReady = false;
+            return emi;
+        }
+    };
+};
+
+#endif // __ARCH_X86_PREDECODER_HH__
diff --git a/src/arch/x86/predecoder_tables.cc b/src/arch/x86/predecoder_tables.cc
new file mode 100644
index 000000000..9304eee47
--- /dev/null
+++ b/src/arch/x86/predecoder_tables.cc
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2007 The Hewlett-Packard Development Company
+ * All rights reserved.
+ *
+ * Redistribution and use of this software in source and binary forms,
+ * with or without modification, are permitted provided that the
+ * following conditions are met:
+ *
+ * The software must be used only for Non-Commercial Use which means any
+ * use which is NOT directed to receiving any direct monetary
+ * compensation for, or commercial advantage from such use.  Illustrative
+ * examples of non-commercial use are academic research, personal study,
+ * teaching, education and corporate research & development.
+ * Illustrative examples of commercial use are distributing products for
+ * commercial advantage and providing services using the software for
+ * commercial advantage.
+ *
+ * If you wish to use this software or functionality therein that may be
+ * covered by patents for commercial use, please contact:
+ *     Director of Intellectual Property Licensing
+ *     Office of Strategy and Technology
+ *     Hewlett-Packard Company
+ *     1501 Page Mill Road
+ *     Palo Alto, California  94304
+ *
+ * Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.  Redistributions
+ * in binary form must reproduce the above copyright notice, this list of
+ * conditions and the following disclaimer in the documentation and/or
+ * other materials provided with the distribution.  Neither the name of
+ * the COPYRIGHT HOLDER(s), HEWLETT-PACKARD COMPANY, nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.  No right of
+ * sublicense is granted herewith.  Derivatives of the software and
+ * output created using the software may be prepared, but only for
+ * Non-Commercial Uses.  Derivatives of the software may be shared with
+ * others provided: (i) the others agree to abide by the list of
+ * conditions herein which includes the Non-Commercial Use restrictions;
+ * and (ii) such Derivatives of the software include the above copyright
+ * notice to acknowledge the contribution from this software where
+ * applicable, this list of conditions and the disclaimer below.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Gabe Black
+ */
+
+#include "arch/x86/predecoder.hh"
+#include "arch/x86/types.hh"
+
+namespace X86ISA
+{
+    const uint8_t CS = CSOverride;
+    const uint8_t DS = DSOverride;
+    const uint8_t ES = ESOverride;
+    const uint8_t FS = FSOverride;
+    const uint8_t GS = GSOverride;
+    const uint8_t SS = SSOverride;
+
+    const uint8_t OO = OperandSizeOverride;
+    const uint8_t AO = AddressSizeOverride;
+    const uint8_t LO = Lock;
+    const uint8_t RE = Rep;
+    const uint8_t RN = Repne;
+    const uint8_t RX = Rex;
+
+    //This table identifies whether a byte is a prefix, and if it is,
+    //which prefix it is.
+    const uint8_t Predecoder::Prefixes[256] =
+    {    //LSB
+// MSB   0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F
+/*   0*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   1*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   2*/ 0 , 0 , 0 , 0 , 0 , 0 , ES, 0 , 0 , 0 , 0 , 0 , 0 , 0 , CS, 0,
+/*   3*/ 0 , 0 , 0 , 0 , 0 , 0 , SS, 0 , 0 , 0 , 0 , 0 , 0 , 0 , DS, 0,
+/*   4*/ RX, RX, RX, RX, RX, RX, RX, RX, RX, RX, RX, RX, RX, RX, RX, RX,
+/*   5*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   6*/ 0 , 0 , 0 , 0 , FS, GS, OO, AO, 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   7*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   8*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   9*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   A*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   B*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   C*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   D*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   E*/ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*   F*/ LO, 0 , RN, RE, 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0
+    };
+
+    //This table identifies whether a particular opcode uses the ModRM byte
+    const uint8_t Predecoder::UsesModRM[2][256] =
+    {//For one byte instructions
+        {    //LSB
+//     MSB   0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F
+/*      0 */ 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0,
+/*      1 */ 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0,
+/*      2 */ 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0,
+/*      3 */ 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0,
+/*      4 */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      5 */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      6 */ 0 , 0 , 1 , 1 , 0 , 0 , 0 , 0 , 0 , 1 , 0 , 1 , 0 , 0 , 0 , 0,
+/*      7 */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      8 */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      9 */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      A */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      B */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      C */ 1 , 1 , 0 , 0 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      D */ 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      E */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      F */ 0 , 0 , 0 , 0 , 0 , 0 , 1 , 1 , 0 , 0 , 0 , 0 , 0 , 0 , 1 , 1
+        },
+    //For two byte instructions
+        {    //LSB
+//     MSB   0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F
+/*      0 */ 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 1 , 0 , 1,
+/*      1 */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      2 */ 1 , 1 , 1 , 1 , 1 , 0 , 1 , 0 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      3 */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      4 */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      5 */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      6 */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      7 */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 0 , 1 , 1 , 1 , 1,
+/*      8 */ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      9 */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      A */ 0 , 0 , 0 , 1 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 1 , 1 , 1 , 1 , 1,
+/*      B */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 0 , 0 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      C */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0,
+/*      D */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      E */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,
+/*      F */ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 0
+        }
+    };
+}
diff --git a/src/arch/x86/types.hh b/src/arch/x86/types.hh
index 3f3c1ca0e..68d95de94 100644
--- a/src/arch/x86/types.hh
+++ b/src/arch/x86/types.hh
@@ -59,18 +59,72 @@
 #define __ARCH_X86_TYPES_HH__
 
 #include <inttypes.h>
+#include <iostream>
 
 namespace X86ISA
 {
     //This really determines how many bytes are passed to the predecoder.
     typedef uint64_t MachInst;
+
+    enum Prefixes {
+        NoOverride = 0,
+        CSOverride = 1,
+        DSOverride = 2,
+        ESOverride = 3,
+        FSOverride = 4,
+        GSOverride = 5,
+        SSOverride = 6,
+        //The Rex prefix obviously doesn't fit in with the above, but putting
+        //it here lets us save double the space the enums take up.
+        Rex = 7,
+        //There can be only one segment override, so they share the
+        //first 3 bits in the legacyPrefixes bitfield.
+        SegmentOverride = 0x7,
+        OperandSizeOverride = 8,
+        AddressSizeOverride = 16,
+        Lock = 32,
+        Rep = 64,
+        Repne = 128
+    };
+
     //The intermediate structure the x86 predecoder returns.
     struct ExtMachInst
     {
-        //Empty for now...
+      public: //XXX These should be hidden in the future
+
+        uint8_t legacyPrefixes;
+        uint8_t rexPrefix;
+        bool twoByteOpcode;
+        uint8_t opcode;
+        uint64_t immediate;
+        uint64_t displacement;
+
+      public:
+
+        //These are to pacify the decoder for now. This will go away once
+        //it can handle non integer inputs, and in the mean time allow me to
+        //excercise the predecoder a little.
+        operator unsigned int()
+        {
+            return 0;
+        }
+
+        ExtMachInst(unsigned int)
+        {;}
+
+        ExtMachInst()
+        {;}
     };
 
-    bool operator == (const ExtMachInst &emi1, const ExtMachInst &emi2)
+    inline static std::ostream &
+        operator << (std::ostream & os, const ExtMachInst & emi)
+    {
+        os << "{X86 ExtMachInst}";
+        return os;
+    }
+
+    inline static bool
+        operator == (const ExtMachInst &emi1, const ExtMachInst &emi2)
     {
         //Since this is empty, it's always equal
         return true;
diff --git a/src/arch/x86/utility.hh b/src/arch/x86/utility.hh
index 0baa249c3..8c5d20c6e 100644
--- a/src/arch/x86/utility.hh
+++ b/src/arch/x86/utility.hh
@@ -59,11 +59,22 @@
 #define __ARCH_X86_UTILITY_HH__
 
 #include "arch/x86/types.hh"
+#include "base/hashmap.hh"
 #include "base/misc.hh"
 #include "sim/host.hh"
 
 class ThreadContext;
 
+namespace __hash_namespace {
+    template<>
+    struct hash<X86ISA::ExtMachInst> {
+        size_t operator()(const X86ISA::ExtMachInst &emi) const {
+            //Because these are all the same, return 0
+            return 0;
+        };
+    };
+}
+
 namespace X86ISA
 {
     static inline bool
@@ -72,18 +83,6 @@ namespace X86ISA
         return false;
     }
 
-    PredecodeResult {
-        MoreBytes = 1,
-        ExtMIReady = 2
-    };
-
-    unsigned int
-    predecode(ExtMachInst &extMachInst, Addr currPC, MachInst machInst,
-            ThreadContext * xc) {
-        //Do something to fill up extMachInst...
-        return MoreBytes | ExtMIReady;
-    }
-
     inline bool isCallerSaveIntegerRegister(unsigned int reg) {
         panic("register classification not implemented");
         return false;