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If a virtual member function has the 'final' attribute, we can devirtualize calls to it.

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llvm-svn: 117444
This commit is contained in:
Anders Carlsson 2010-10-27 13:28:46 +00:00
parent 258b8e1dc8
commit a7911fa3d7
3 changed files with 25 additions and 4 deletions
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1
clang/clang.xcodeproj/project.pbxproj
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@ -2039,6 +2039,7 @@
isa = PBXProject; isa = PBXProject;
buildConfigurationList = 1DEB923508733DC60010E9CD /* Build configuration list for PBXProject "clang" */; buildConfigurationList = 1DEB923508733DC60010E9CD /* Build configuration list for PBXProject "clang" */;
compatibilityVersion = "Xcode 2.4"; compatibilityVersion = "Xcode 2.4";
developmentRegion = English;
hasScannedForEncodings = 1; hasScannedForEncodings = 1;
knownRegions = ( knownRegions = (
English, English,

15
clang/lib/CodeGen/CGExprCXX.cpp
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@ -55,7 +55,14 @@ RValue CodeGenFunction::EmitCXXMemberCall(const CXXMethodDecl *MD,
/// canDevirtualizeMemberFunctionCalls - Checks whether virtual calls on given /// canDevirtualizeMemberFunctionCalls - Checks whether virtual calls on given
/// expr can be devirtualized. /// expr can be devirtualized.
static bool canDevirtualizeMemberFunctionCalls(const Expr *Base) { static bool canDevirtualizeMemberFunctionCalls(const Expr *Base,
const CXXMethodDecl *MD) {
// If the member function has the "final" attribute, we know that it can't be
// overridden and can therefor devirtualize it.
if (MD->hasAttr<FinalAttr>())
return true;
if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base)) { if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base)) {
if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) { if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
// This is a record decl. We know the type and can devirtualize it. // This is a record decl. We know the type and can devirtualize it.
@ -76,7 +83,7 @@ static bool canDevirtualizeMemberFunctionCalls(const Expr *Base) {
// Check if this is a call expr that returns a record type. // Check if this is a call expr that returns a record type.
if (const CallExpr *CE = dyn_cast<CallExpr>(Base)) if (const CallExpr *CE = dyn_cast<CallExpr>(Base))
return CE->getCallReturnType()->isRecordType(); return CE->getCallReturnType()->isRecordType();
// We can't devirtualize the call. // We can't devirtualize the call.
return false; return false;
} }
@ -152,7 +159,7 @@ RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE,
// We also don't emit a virtual call if the base expression has a record type // We also don't emit a virtual call if the base expression has a record type
// because then we know what the type is. // because then we know what the type is.
bool UseVirtualCall = MD->isVirtual() && !ME->hasQualifier() bool UseVirtualCall = MD->isVirtual() && !ME->hasQualifier()
&& !canDevirtualizeMemberFunctionCalls(ME->getBase()); && !canDevirtualizeMemberFunctionCalls(ME->getBase(), MD);
llvm::Value *Callee; llvm::Value *Callee;
if (const CXXDestructorDecl *Dtor = dyn_cast<CXXDestructorDecl>(MD)) { if (const CXXDestructorDecl *Dtor = dyn_cast<CXXDestructorDecl>(MD)) {
@ -267,7 +274,7 @@ CodeGenFunction::EmitCXXOperatorMemberCallExpr(const CXXOperatorCallExpr *E,
This = LV.getAddress(); This = LV.getAddress();
llvm::Value *Callee; llvm::Value *Callee;
if (MD->isVirtual() && !canDevirtualizeMemberFunctionCalls(E->getArg(0))) if (MD->isVirtual() && !canDevirtualizeMemberFunctionCalls(E->getArg(0), MD))
Callee = BuildVirtualCall(MD, This, Ty); Callee = BuildVirtualCall(MD, This, Ty);
else else
Callee = CGM.GetAddrOfFunction(MD, Ty); Callee = CGM.GetAddrOfFunction(MD, Ty);

13
clang/test/CodeGenCXX/attr-final-devirtualize-virtual-function-calls.cpp Normal file
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@ -0,0 +1,13 @@
// RUN: %clang_cc1 %s -O3 -emit-llvm -o - | FileCheck %s
namespace Test1 {
struct A {
virtual int f() __attribute__((final)) { return 1; }
};
// CHECK: define i32 @_ZN5Test11fEPNS_1AE
int f(A* a) {
// CHECK: ret i32 1
return a->f();
}
}