From a0cd970b81ea0a292f0fbbe7f0113746bfe8de5a Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper@gmail.com>
Date: Thu, 9 Feb 2012 08:58:07 +0000
Subject: [PATCH] More tweaks to get the size of the X86 disassembler tables
 down.

llvm-svn: 150167
---
 .../X86/Disassembler/X86DisassemblerDecoder.c |  4 +++
 .../X86DisassemblerDecoderCommon.h            |  3 ++
 llvm/utils/TableGen/X86DisassemblerTables.cpp | 35 +++++++++++++++----
 3 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c b/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
index 9a628f2163d0..a7becdb2c70c 100644
--- a/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
+++ b/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
@@ -136,6 +136,10 @@ static InstrUID decode(OpcodeType type,
     if (modFromModRM(modRM) == 0x3)
       return modRMTable[dec->instructionIDs+1];
     return modRMTable[dec->instructionIDs];
+  case MODRM_SPLITREG:
+    if (modFromModRM(modRM) == 0x3)
+      return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)+8];
+    return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)];
   case MODRM_FULL:
     return modRMTable[dec->instructionIDs+modRM];
   }
diff --git a/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h b/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
index a7ef0cc4325d..d6b23c0af4f1 100644
--- a/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
+++ b/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
@@ -156,6 +156,8 @@ typedef uint16_t InstrUID;
  * MODRM_SPLITRM  - If the ModR/M byte is between 0x00 and 0xbf, the opcode
  *                  corresponds to one instruction; otherwise, it corresponds to
  *                  a different instruction.
+ * MODRM_SPLITREG - ModR/M byte divided by 8 is used to select instruction. This
+                    corresponds to instructions that use reg field as opcode
  * MODRM_FULL     - Potentially, each value of the ModR/M byte could correspond
  *                  to a different instruction.
  */
@@ -163,6 +165,7 @@ typedef uint16_t InstrUID;
 #define MODRMTYPES            \
   ENUM_ENTRY(MODRM_ONEENTRY)  \
   ENUM_ENTRY(MODRM_SPLITRM)   \
+  ENUM_ENTRY(MODRM_SPLITREG)  \
   ENUM_ENTRY(MODRM_FULL)
 
 #define ENUM_ENTRY(n) n,    
diff --git a/llvm/utils/TableGen/X86DisassemblerTables.cpp b/llvm/utils/TableGen/X86DisassemblerTables.cpp
index 7db39b8481d6..b5f970d3548c 100644
--- a/llvm/utils/TableGen/X86DisassemblerTables.cpp
+++ b/llvm/utils/TableGen/X86DisassemblerTables.cpp
@@ -208,28 +208,40 @@ static ModRMDecisionType getDecisionType(ModRMDecision &decision)
 {
   bool satisfiesOneEntry = true;
   bool satisfiesSplitRM = true;
-  
+  bool satisfiesSplitReg = true;
+
   uint16_t index;
-  
+
   for (index = 0; index < 256; ++index) {
     if (decision.instructionIDs[index] != decision.instructionIDs[0])
       satisfiesOneEntry = false;
-    
+
     if (((index & 0xc0) == 0xc0) &&
        (decision.instructionIDs[index] != decision.instructionIDs[0xc0]))
       satisfiesSplitRM = false;
-    
+
     if (((index & 0xc0) != 0xc0) &&
        (decision.instructionIDs[index] != decision.instructionIDs[0x00]))
       satisfiesSplitRM = false;
+
+    if (((index & 0xc0) == 0xc0) &&
+       (decision.instructionIDs[index] != decision.instructionIDs[index&0xf8]))
+      satisfiesSplitReg = false;
+
+    if (((index & 0xc0) != 0xc0) &&
+       (decision.instructionIDs[index] != decision.instructionIDs[index&0x38]))
+      satisfiesSplitReg = false;
   }
-  
+
   if (satisfiesOneEntry)
     return MODRM_ONEENTRY;
-  
+
   if (satisfiesSplitRM)
     return MODRM_SPLITRM;
-  
+
+  if (satisfiesSplitReg)
+    return MODRM_SPLITREG;
+
   return MODRM_FULL;
 }
 
@@ -322,6 +334,12 @@ void DisassemblerTables::emitModRMDecision(raw_ostream &o1,
       emitOneID(o1, i1, decision.instructionIDs[0x00], true); // mod = 0b00
       emitOneID(o1, i1, decision.instructionIDs[0xc0], true); // mod = 0b11
       break;
+    case MODRM_SPLITREG:
+      for (index = 0; index < 64; index += 8)
+        emitOneID(o1, i1, decision.instructionIDs[index], true);
+      for (index = 0xc0; index < 256; index += 8)
+        emitOneID(o1, i1, decision.instructionIDs[index], true);
+      break;
     case MODRM_FULL:
       for (index = 0; index < 256; ++index)
         emitOneID(o1, i1, decision.instructionIDs[index], true);
@@ -348,6 +366,9 @@ void DisassemblerTables::emitModRMDecision(raw_ostream &o1,
     case MODRM_SPLITRM:
       sEntryNumber += 2;
       break;
+    case MODRM_SPLITREG:
+      sEntryNumber += 16;
+      break;
     case MODRM_FULL:
       sEntryNumber += 256;
       break;