From c4107aa8c2299d6f869b170faf0dcd23e81f5a82 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper@gmail.com>
Date: Tue, 18 Sep 2012 06:10:45 +0000
Subject: [PATCH] Use variable type for index into mnemonic table. Shrinks size
 of index field on in tree targets. Saving static data space.

llvm-svn: 164108
---
 utils/TableGen/AsmMatcherEmitter.cpp | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/utils/TableGen/AsmMatcherEmitter.cpp b/utils/TableGen/AsmMatcherEmitter.cpp
index b7f98a00822..338a0b2fd24 100644
--- a/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/utils/TableGen/AsmMatcherEmitter.cpp
@@ -2681,11 +2681,21 @@ void AsmMatcherEmitter::run(raw_ostream &OS) {
   emitComputeAvailableFeatures(Info, OS);
 
 
+  StringToOffsetTable StringTable;
+
   size_t MaxNumOperands = 0;
+  unsigned MaxMnemonicIndex = 0;
   for (std::vector<MatchableInfo*>::const_iterator it =
          Info.Matchables.begin(), ie = Info.Matchables.end();
-       it != ie; ++it)
-    MaxNumOperands = std::max(MaxNumOperands, (*it)->AsmOperands.size());
+       it != ie; ++it) {
+    MatchableInfo &II = **it;
+    MaxNumOperands = std::max(MaxNumOperands, II.AsmOperands.size());
+
+    // Store a pascal-style length byte in the mnemonic.
+    std::string LenMnemonic = char(II.Mnemonic.size()) + II.Mnemonic.str();
+    MaxMnemonicIndex = std::max(MaxMnemonicIndex,
+                        StringTable.GetOrAddStringOffset(LenMnemonic, false));
+  }
 
   // Emit the static match table; unused classes get initalized to 0 which is
   // guaranteed to be InvalidMatchClass.
@@ -2700,7 +2710,8 @@ void AsmMatcherEmitter::run(raw_ostream &OS) {
   OS << "namespace {\n";
   OS << "  struct MatchEntry {\n";
   OS << "    static const char *const MnemonicTable;\n";
-  OS << "    uint32_t Mnemonic;\n";
+  OS << "    " << getMinimalTypeForRange(MaxMnemonicIndex)
+               << " Mnemonic;\n";
   OS << "    uint16_t Opcode;\n";
   OS << "    " << getMinimalTypeForRange(Info.Matchables.size())
                << " ConvertFn;\n";
@@ -2730,8 +2741,6 @@ void AsmMatcherEmitter::run(raw_ostream &OS) {
 
   OS << "} // end anonymous namespace.\n\n";
 
-  StringToOffsetTable StringTable;
-
   OS << "static const MatchEntry MatchTable["
      << Info.Matchables.size() << "] = {\n";