IRgen optimization: cache the value of 'this' and 'vtt' instead of

repeatedly reloading from an alloca.  We still need to create the alloca
for debug info purposes (although we currently create it in all cases
because of some abstraction boundaries that're hard to break down).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@96403 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 19 insertions, 25 deletions

diff --git a/lib/CodeGen/CGCXX.cpp b/lib/CodeGen/CGCXX.cpp
index 28c4c6b4b5..c4c52aac03 100644
--- a/lib/CodeGen/CGCXX.cpp
+++ b/lib/CodeGen/CGCXX.cpp
@@ -28,18 +28,6 @@ using namespace CodeGen;
 
 
 
-llvm::Value *CodeGenFunction::LoadCXXThis() {
-  assert(isa<CXXMethodDecl>(CurFuncDecl) &&
-         "Must be in a C++ member function decl to load 'this'");
-  assert(cast<CXXMethodDecl>(CurFuncDecl)->isInstance() &&
-         "Must be in a C++ member function decl to load 'this'");
-
-  // FIXME: What if we're inside a block?
-  // ans: See how CodeGenFunction::LoadObjCSelf() uses
-  // CodeGenFunction::BlockForwardSelf() for how to do this.
-  return Builder.CreateLoad(LocalDeclMap[CXXThisDecl], "this");
-}
-
 void CodeGenModule::EmitCXXConstructors(const CXXConstructorDecl *D) {
   EmitGlobal(GlobalDecl(D, Ctor_Complete));
   EmitGlobal(GlobalDecl(D, Ctor_Base));
diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index fa5a47f315..d9051675ba 100644
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -1405,11 +1405,3 @@ void CodeGenFunction::InitializeVtablePtrsRecursive(
   // Store address point
   Builder.CreateStore(VtableAddressPoint, VtableField);
 }
-
-llvm::Value *CodeGenFunction::LoadCXXVTT() {
-  assert((isa<CXXConstructorDecl>(CurFuncDecl) ||
-          isa<CXXDestructorDecl>(CurFuncDecl)) &&
-         "Must be in a C++ ctor or dtor to load the vtt parameter");
-
-  return Builder.CreateLoad(LocalDeclMap[CXXVTTDecl], "vtt");
-}
diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index febffc9697..d803a05aa9 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -30,7 +30,7 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
     Builder(cgm.getModule().getContext()),
     DebugInfo(0), IndirectBranch(0),
     SwitchInsn(0), CaseRangeBlock(0), InvokeDest(0),
-    CXXThisDecl(0), CXXVTTDecl(0),
+    CXXThisDecl(0), CXXThisValue(0), CXXVTTDecl(0), CXXVTTValue(0),
     ConditionalBranchLevel(0), TerminateHandler(0), TrapBB(0),
     UniqueAggrDestructorCount(0) {
   LLVMIntTy = ConvertType(getContext().IntTy);
@@ -225,6 +225,11 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
   EmitStartEHSpec(CurCodeDecl);
   EmitFunctionProlog(*CurFnInfo, CurFn, Args);
 
+  if (CXXThisDecl)
+    CXXThisValue = Builder.CreateLoad(LocalDeclMap[CXXThisDecl], "this");
+  if (CXXVTTDecl)
+    CXXVTTValue = Builder.CreateLoad(LocalDeclMap[CXXVTTDecl], "vtt");
+
   // If any of the arguments have a variably modified type, make sure to
   // emit the type size.
   for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
@@ -252,7 +257,8 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn) {
       // Create the implicit 'this' decl.
       // FIXME: I'm not entirely sure I like using a fake decl just for code
       // generation. Maybe we can come up with a better way?
-      CXXThisDecl = ImplicitParamDecl::Create(getContext(), 0, SourceLocation(),
+      CXXThisDecl = ImplicitParamDecl::Create(getContext(), 0,
+                                              FD->getLocation(),
                                               &getContext().Idents.get("this"),
                                               MD->getThisType(getContext()));
       Args.push_back(std::make_pair(CXXThisDecl, CXXThisDecl->getType()));
@@ -262,7 +268,7 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn) {
         // FIXME: The comment about using a fake decl above applies here too.
         QualType T = getContext().getPointerType(getContext().VoidPtrTy);
         CXXVTTDecl = 
-          ImplicitParamDecl::Create(getContext(), 0, SourceLocation(),
+          ImplicitParamDecl::Create(getContext(), 0, FD->getLocation(),
                                     &getContext().Idents.get("vtt"), T);
         Args.push_back(std::make_pair(CXXVTTDecl, CXXVTTDecl->getType()));
       }
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index a4db556d39..a694b894df 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -382,11 +382,13 @@ private:
   /// CXXThisDecl - When generating code for a C++ member function,
   /// this will hold the implicit 'this' declaration.
   ImplicitParamDecl *CXXThisDecl;
+  llvm::Value *CXXThisValue;
 
   /// CXXVTTDecl - When generating code for a base object constructor or
   /// base object destructor with virtual bases, this will hold the implicit
   /// VTT parameter.
   ImplicitParamDecl *CXXVTTDecl;
+  llvm::Value *CXXVTTValue;
   
   /// CXXLiveTemporaryInfo - Holds information about a live C++ temporary.
   struct CXXLiveTemporaryInfo {
@@ -745,11 +747,17 @@ public:
 
   /// LoadCXXThis - Load the value of 'this'. This function is only valid while
   /// generating code for an C++ member function.
-  llvm::Value *LoadCXXThis();
+  llvm::Value *LoadCXXThis() {
+    assert(CXXThisValue && "no 'this' value for this function");
+    return CXXThisValue;
+  }
 
   /// LoadCXXVTT - Load the VTT parameter to base constructors/destructors have
   /// virtual bases.
-  llvm::Value *LoadCXXVTT();
+  llvm::Value *LoadCXXVTT() {
+    assert(CXXVTTValue && "no VTT value for this function");
+    return CXXVTTValue;
+  }
 
   /// GetAddressOfBaseOfCompleteClass - Convert the given pointer to a
   /// complete class down to one of its virtual bases.