From 76b29b518dad5e719077a1066e242fa91f777a7c Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper@gmail.com>
Date: Thu, 13 Sep 2012 05:45:42 +0000
Subject: [PATCH] Add a new compression type to ModRM table that detects when
 the memory modRM byte represent 8 instructions and the reg modRM byte
 represents up to 64 instructions. Reduces modRM table from 43k entreis to 25k
 entries. Based on a patch from Manman Ren.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163774 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../X86/Disassembler/X86DisassemblerDecoder.c   |  4 ++++
 .../Disassembler/X86DisassemblerDecoderCommon.h |  5 +++++
 utils/TableGen/X86DisassemblerTables.cpp        | 17 +++++++++++++++--
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c b/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
index af444d196eb..b24f5172099 100644
--- a/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
+++ b/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
@@ -138,6 +138,10 @@ static InstrUID decode(OpcodeType type,
     if (modFromModRM(modRM) == 0x3)
       return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)+8];
     return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)];
+  case MODRM_SPLITMISC:
+    if (modFromModRM(modRM) == 0x3)
+      return modRMTable[dec->instructionIDs+(modRM & 0x3f)+8];
+    return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)];
   case MODRM_FULL:
     return modRMTable[dec->instructionIDs+modRM];
   }
diff --git a/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h b/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
index b0a0e1e78ef..23dfe4b5b5f 100644
--- a/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
+++ b/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
@@ -160,6 +160,10 @@ 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_SPLITMISC- If the ModR/M byte is between 0x00 and 0xbf, ModR/M byte
+ *                  divided by 8 is used to select instruction; otherwise, each
+ *                  value of the ModR/M byte could correspond 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
@@ -169,6 +173,7 @@ typedef uint16_t InstrUID;
 #define MODRMTYPES            \
   ENUM_ENTRY(MODRM_ONEENTRY)  \
   ENUM_ENTRY(MODRM_SPLITRM)   \
+  ENUM_ENTRY(MODRM_SPLITMISC)  \
   ENUM_ENTRY(MODRM_SPLITREG)  \
   ENUM_ENTRY(MODRM_FULL)
 
diff --git a/utils/TableGen/X86DisassemblerTables.cpp b/utils/TableGen/X86DisassemblerTables.cpp
index 8526621599a..468a1f81c71 100644
--- a/utils/TableGen/X86DisassemblerTables.cpp
+++ b/utils/TableGen/X86DisassemblerTables.cpp
@@ -209,6 +209,7 @@ static ModRMDecisionType getDecisionType(ModRMDecision &decision) {
   bool satisfiesOneEntry = true;
   bool satisfiesSplitRM = true;
   bool satisfiesSplitReg = true;
+  bool satisfiesSplitMisc = true;
 
   for (unsigned index = 0; index < 256; ++index) {
     if (decision.instructionIDs[index] != decision.instructionIDs[0])
@@ -228,7 +229,7 @@ static ModRMDecisionType getDecisionType(ModRMDecision &decision) {
 
     if (((index & 0xc0) != 0xc0) &&
        (decision.instructionIDs[index] != decision.instructionIDs[index&0x38]))
-      satisfiesSplitReg = false;
+      satisfiesSplitMisc = false;
   }
 
   if (satisfiesOneEntry)
@@ -237,9 +238,12 @@ static ModRMDecisionType getDecisionType(ModRMDecision &decision) {
   if (satisfiesSplitRM)
     return MODRM_SPLITRM;
 
-  if (satisfiesSplitReg)
+  if (satisfiesSplitReg && satisfiesSplitMisc)
     return MODRM_SPLITREG;
 
+  if (satisfiesSplitMisc)
+    return MODRM_SPLITMISC;
+
   return MODRM_FULL;
 }
 
@@ -332,6 +336,12 @@ void DisassemblerTables::emitModRMDecision(raw_ostream &o1, raw_ostream &o2,
       for (unsigned index = 0xc0; index < 256; index += 8)
         emitOneID(o1, i1, decision.instructionIDs[index], true);
       break;
+    case MODRM_SPLITMISC:
+      for (unsigned index = 0; index < 64; index += 8)
+        emitOneID(o1, i1, decision.instructionIDs[index], true);
+      for (unsigned index = 0xc0; index < 256; ++index)
+        emitOneID(o1, i1, decision.instructionIDs[index], true);
+      break;
     case MODRM_FULL:
       for (unsigned index = 0; index < 256; ++index)
         emitOneID(o1, i1, decision.instructionIDs[index], true);
@@ -361,6 +371,9 @@ void DisassemblerTables::emitModRMDecision(raw_ostream &o1, raw_ostream &o2,
     case MODRM_SPLITREG:
       sEntryNumber += 16;
       break;
+    case MODRM_SPLITMISC:
+      sEntryNumber += 8 + 64;
+      break;
     case MODRM_FULL:
       sEntryNumber += 256;
       break;