Part of PR39508: Emit an @llvm.invariant.start after storing to
__tls_guard.
__tls_guard can only ever transition from 0 to 1, and only once. This
permits LLVM to remove repeated checks for TLS initialization and
repeated initialization code in cases like:
int g();
thread_local int n = g();
int a = n + n;
where we could not prove that __tls_guard was still 'true' when checking
it for the second reference to 'n' in the initializer of 'a'.
llvm-svn: 345774
diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index b7daba6..07fb4c0 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -124,22 +124,26 @@
/// constant from this point onwards.
static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
llvm::Constant *Addr) {
+ return CGF.EmitInvariantStart(
+ Addr, CGF.getContext().getTypeSizeInChars(D.getType()));
+}
+
+void CodeGenFunction::EmitInvariantStart(llvm::Constant *Addr, CharUnits Size) {
// Do not emit the intrinsic if we're not optimizing.
- if (!CGF.CGM.getCodeGenOpts().OptimizationLevel)
+ if (!CGM.getCodeGenOpts().OptimizationLevel)
return;
// Grab the llvm.invariant.start intrinsic.
llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
// Overloaded address space type.
- llvm::Type *ObjectPtr[1] = {CGF.Int8PtrTy};
- llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID, ObjectPtr);
+ llvm::Type *ObjectPtr[1] = {Int8PtrTy};
+ llvm::Constant *InvariantStart = CGM.getIntrinsic(InvStartID, ObjectPtr);
// Emit a call with the size in bytes of the object.
- CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType());
- uint64_t Width = WidthChars.getQuantity();
- llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width),
- llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)};
- CGF.Builder.CreateCall(InvariantStart, Args);
+ uint64_t Width = Size.getQuantity();
+ llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(Int64Ty, Width),
+ llvm::ConstantExpr::getBitCast(Addr, Int8PtrTy)};
+ Builder.CreateCall(InvariantStart, Args);
}
void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
@@ -607,7 +611,7 @@
void
CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
ArrayRef<llvm::Function *> Decls,
- Address Guard) {
+ ConstantAddress Guard) {
{
auto NL = ApplyDebugLocation::CreateEmpty(*this);
StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
@@ -631,6 +635,12 @@
// initializers use previously-initialized thread_local vars, that's
// probably supposed to be OK, but the standard doesn't say.
Builder.CreateStore(llvm::ConstantInt::get(GuardVal->getType(),1), Guard);
+
+ // The guard variable can't ever change again.
+ EmitInvariantStart(
+ Guard.getPointer(),
+ CharUnits::fromQuantity(
+ CGM.getDataLayout().getTypeAllocSize(GuardVal->getType())));
}
RunCleanupsScope Scope(*this);
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index c73cef5..d5de0a0 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -3892,6 +3892,8 @@
AddInitializerToStaticVarDecl(const VarDecl &D,
llvm::GlobalVariable *GV);
+ // Emit an @llvm.invariant.start call for the given memory region.
+ void EmitInvariantStart(llvm::Constant *Addr, CharUnits Size);
/// EmitCXXGlobalVarDeclInit - Create the initializer for a C++
/// variable with global storage.
@@ -3927,9 +3929,10 @@
/// GenerateCXXGlobalInitFunc - Generates code for initializing global
/// variables.
- void GenerateCXXGlobalInitFunc(llvm::Function *Fn,
- ArrayRef<llvm::Function *> CXXThreadLocals,
- Address Guard = Address::invalid());
+ void
+ GenerateCXXGlobalInitFunc(llvm::Function *Fn,
+ ArrayRef<llvm::Function *> CXXThreadLocals,
+ ConstantAddress Guard = ConstantAddress::invalid());
/// GenerateCXXGlobalDtorsFunc - Generates code for destroying global
/// variables.
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index a7e3c8d..b67a64b 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2472,8 +2472,8 @@
CharUnits GuardAlign = CharUnits::One();
Guard->setAlignment(GuardAlign.getQuantity());
- CodeGenFunction(CGM).GenerateCXXGlobalInitFunc(InitFunc, OrderedInits,
- Address(Guard, GuardAlign));
+ CodeGenFunction(CGM).GenerateCXXGlobalInitFunc(
+ InitFunc, OrderedInits, ConstantAddress(Guard, GuardAlign));
// On Darwin platforms, use CXX_FAST_TLS calling convention.
if (CGM.getTarget().getTriple().isOSDarwin()) {
InitFunc->setCallingConv(llvm::CallingConv::CXX_FAST_TLS);