From f415d8b64687d4db7e1986b74e9da6cae72c0fd1 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Mon, 23 May 2011 00:18:33 +0000
Subject: [PATCH] Use a more efficient data structure for the "operand map".
 The number of operands to an instruction aren't great, so an iterative search
 is fairly quick and doesn't have the overhead of std::map.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131886 91177308-0d34-0410-b5e6-96231b3b80d8
---
 utils/TableGen/AsmWriterEmitter.cpp | 35 +++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/utils/TableGen/AsmWriterEmitter.cpp b/utils/TableGen/AsmWriterEmitter.cpp
index 2b1a4cc8a3d..e6deb6908e0 100644
--- a/utils/TableGen/AsmWriterEmitter.cpp
+++ b/utils/TableGen/AsmWriterEmitter.cpp
@@ -670,8 +670,8 @@ public:
 
     for (std::map<StringRef, unsigned>::iterator
            I = OpMap.begin(), E = OpMap.end(); I != E; ++I)
-      O.indent(6) << "OpMap[\"" << I->first << "\"] = "
-                  << I->second << ";\n";
+      O.indent(6) << "OpMap.push_back(std::make_pair(\"" << I->first << "\", "
+                  << I->second << "));\n";
 
     O.indent(6) << "break;\n";
     O.indent(4) << '}';
@@ -754,6 +754,20 @@ static void EmitComputeAvailableFeatures(AsmWriterInfo &Info,
   O << "}\n\n";
 }
 
+static void EmitGetMapOperandNumber(raw_ostream &O) {
+  O << "static unsigned getMapOperandNumber("
+    << "const SmallVectorImpl<std::pair<StringRef, unsigned> > &OpMap,\n";
+  O << "                                    StringRef Name) {\n";
+  O << "  for (SmallVectorImpl<std::pair<StringRef, unsigned> >::"
+    << "const_iterator\n";
+  O << "         I = OpMap.begin(), E = OpMap.end(); I != E; ++I)\n";
+  O << "    if (I->first == Name)\n";
+  O << "      return I->second;\n";
+  O << "  assert(false && \"Operand not in map!\");\n";
+  O << "  return 0;\n";
+  O << "}\n\n";
+}
+
 void AsmWriterEmitter::EmitRegIsInRegClass(raw_ostream &O) {
   CodeGenTarget Target(Records);
 
@@ -934,9 +948,12 @@ void AsmWriterEmitter::EmitPrintAliasInstruction(raw_ostream &O) {
   EmitSubtargetFeatureFlagEnumeration(AWI, O);
   EmitComputeAvailableFeatures(AWI, AsmWriter, Target, O);
 
-  O << "bool " << Target.getName() << ClassName
-    << "::printAliasInstr(const " << MachineInstrClassName
-    << " *MI, raw_ostream &OS) {\n";
+  std::string Header;
+  raw_string_ostream HeaderO(Header);
+
+  HeaderO << "bool " << Target.getName() << ClassName
+          << "::printAliasInstr(const " << MachineInstrClassName
+          << " *MI, raw_ostream &OS) {\n";
 
   std::string Cases;
   raw_string_ostream CasesO(Cases);
@@ -979,14 +996,18 @@ void AsmWriterEmitter::EmitPrintAliasInstruction(raw_ostream &O) {
   }
 
   if (CasesO.str().empty() || !isMC) {
+    O << HeaderO.str();
     O << "  return false;\n";
     O << "}\n\n";
     O << "#endif // PRINT_ALIAS_INSTR\n";
     return;
   }
 
+  EmitGetMapOperandNumber(O);
+
+  O << HeaderO.str();
   O.indent(2) << "StringRef AsmString;\n";
-  O.indent(2) << "std::map<StringRef, unsigned> OpMap;\n";
+  O.indent(2) << "SmallVector<std::pair<StringRef, unsigned>, 4> OpMap;\n";
   if (NeedAvailableFeatures)
     O.indent(2) << "unsigned AvailableFeatures = getAvailableFeatures();\n\n";
   O.indent(2) << "switch (MI->getOpcode()) {\n";
@@ -1012,7 +1033,7 @@ void AsmWriterEmitter::EmitPrintAliasInstruction(raw_ostream &O) {
   O << "                *I == '_'))\n";
   O << "          ++I;\n";
   O << "        StringRef Name(Start, I - Start);\n";
-  O << "        printOperand(MI, OpMap[Name], OS);\n";
+  O << "        printOperand(MI, getMapOperandNumber(OpMap, Name), OS);\n";
   O << "      } else {\n";
   O << "        OS << *I++;\n";
   O << "      }\n";