Author: rsmith
Date: Wed Oct 31 13:39:26 2018
New Revision: 345774
URL: http://llvm.org/viewvc/llvm-project?rev=345774&view=rev
Log:
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'.
Modified:
cfe/trunk/lib/CodeGen/CGDeclCXX.cpp
cfe/trunk/lib/CodeGen/CodeGenFunction.h
cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
cfe/trunk/test/CodeGenCXX/cxx11-thread-local.cpp
Modified: cfe/trunk/lib/CodeGen/CGDeclCXX.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDeclCXX.cpp?rev=345774&r1=345773&r2=345774&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGDeclCXX.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGDeclCXX.cpp Wed Oct 31 13:39:26 2018
@@ -124,22 +124,26 @@ static void EmitDeclDestroy(CodeGenFunct
/// 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::GenerateCXXGlobalV
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 @@ CodeGenFunction::GenerateCXXGlobalInitFu
// 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);
Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=345774&r1=345773&r2=345774&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original)
+++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Wed Oct 31 13:39:26 2018
@@ -3892,6 +3892,8 @@ public:
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 @@ public:
/// 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.
Modified: cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp?rev=345774&r1=345773&r2=345774&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp (original)
+++ cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp Wed Oct 31 13:39:26 2018
@@ -2472,8 +2472,8 @@ void ItaniumCXXABI::EmitThreadLocalInitF
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);
Modified: cfe/trunk/test/CodeGenCXX/cxx11-thread-local.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/cxx11-thread-local.cpp?rev=345774&r1=345773&r2=345774&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/cxx11-thread-local.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/cxx11-thread-local.cpp Wed Oct 31 13:39:26 2018
@@ -1,4 +1,5 @@
// RUN: %clang_cc1 -std=c++11 -emit-llvm %s -o - -triple x86_64-linux-gnu |
FileCheck --check-prefix=CHECK --check-prefix=LINUX %s
+// RUN: %clang_cc1 -std=c++11 -emit-llvm %s -O2 -disable-llvm-passes -o -
-triple x86_64-linux-gnu | FileCheck --check-prefix=CHECK --check-prefix=LINUX
--check-prefix=CHECK-OPT %s
// RUN: %clang_cc1 -std=c++11 -femulated-tls -emit-llvm %s -o - \
// RUN: -triple x86_64-linux-gnu 2>&1 | FileCheck --check-prefix=CHECK
--check-prefix=LINUX %s
// RUN: %clang_cc1 -std=c++11 -emit-llvm %s -o - -triple x86_64-apple-darwin12
| FileCheck --check-prefix=CHECK --check-prefix=DARWIN %s
@@ -307,6 +308,7 @@ void set_anon_i() {
// CHECK: br i1 %[[NEED_TLS_INIT]],
// init:
// CHECK: store i8 1, i8* @__tls_guard
+// CHECK-OPT: call {}* @llvm.invariant.start.p0i8(i64 1, i8* @__tls_guard)
// CHECK-NOT: call void @[[V_M_INIT]]()
// CHECK: call void @[[A_INIT]]()
// CHECK-NOT: call void @[[V_M_INIT]]()
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