[clang] [Clang] Add fake use emission to Clang with -fextend-lifetimes (PR #110102)
Stephen Tozer via cfe-commits
cfe-commits at lists.llvm.org
Thu Sep 26 03:36:39 PDT 2024
https://github.com/SLTozer updated https://github.com/llvm/llvm-project/pull/110102
>From 7d8646edb373c38ee761de2c338c45b967a423e7 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.tozer at sony.com>
Date: Wed, 25 Sep 2024 16:55:39 +0100
Subject: [PATCH] [Clang] Add fake use emission to Clang with
-fextend-lifetimes
Following the previous patch which adds the "extend lifetimes" flag
without (almost) any functionality, this patch adds the real feature by
allowing Clang to emit fake uses. These are emitted as a new form of cleanup,
set for variable addresses, which just emits a fake use intrinsic when the
variable falls out of scope. The code for achieving this is simple, with most
of the logic centered on determining whether to emit a fake use for a given
address, and on ensuring that fake uses are ignored in a few cases.
---
clang/lib/CodeGen/CGCall.cpp | 17 +++++-
clang/lib/CodeGen/CGCleanup.cpp | 7 ++-
clang/lib/CodeGen/CGCleanup.h | 8 +++
clang/lib/CodeGen/CGDecl.cpp | 69 +++++++++++++++++++++++
clang/lib/CodeGen/CodeGenFunction.cpp | 6 +-
clang/lib/CodeGen/CodeGenFunction.h | 16 ++++++
clang/lib/CodeGen/CodeGenModule.h | 4 ++
clang/lib/CodeGen/EHScopeStack.h | 9 ++-
clang/test/CodeGen/extend-liveness1.c | 29 ++++++++++
clang/test/CodeGen/extend-liveness2.cpp | 34 +++++++++++
clang/test/CodeGen/fake-use-determinism.c | 18 ++++++
clang/test/CodeGen/fake-use-lambda.cpp | 43 ++++++++++++++
clang/test/CodeGen/fake-use-landingpad.c | 16 ++++++
clang/test/CodeGen/fake-use-noreturn.cpp | 27 +++++++++
clang/test/CodeGen/fake-use-return-line.c | 15 +++++
clang/test/CodeGen/fake-use-sanitizer.cpp | 37 ++++++++++++
clang/test/CodeGen/fake-use-scalar.c | 22 ++++++++
clang/test/CodeGen/fake-use-small-aggs.c | 24 ++++++++
clang/test/CodeGen/fake-use-while.c | 18 ++++++
clang/test/CodeGen/fake-use.cpp | 44 +++++++++++++++
clang/test/CodeGen/no-fake-use-O0.cpp | 50 ++++++++++++++++
21 files changed, 503 insertions(+), 10 deletions(-)
create mode 100644 clang/test/CodeGen/extend-liveness1.c
create mode 100644 clang/test/CodeGen/extend-liveness2.cpp
create mode 100644 clang/test/CodeGen/fake-use-determinism.c
create mode 100644 clang/test/CodeGen/fake-use-lambda.cpp
create mode 100644 clang/test/CodeGen/fake-use-landingpad.c
create mode 100644 clang/test/CodeGen/fake-use-noreturn.cpp
create mode 100644 clang/test/CodeGen/fake-use-return-line.c
create mode 100644 clang/test/CodeGen/fake-use-sanitizer.cpp
create mode 100644 clang/test/CodeGen/fake-use-scalar.c
create mode 100644 clang/test/CodeGen/fake-use-small-aggs.c
create mode 100644 clang/test/CodeGen/fake-use-while.c
create mode 100644 clang/test/CodeGen/fake-use.cpp
create mode 100644 clang/test/CodeGen/no-fake-use-O0.cpp
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 4ae981e4013e9c..26441b4135529d 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -3566,15 +3566,26 @@ static llvm::StoreInst *findDominatingStoreToReturnValue(CodeGenFunction &CGF) {
llvm::BasicBlock *IP = CGF.Builder.GetInsertBlock();
if (IP->empty()) return nullptr;
- // Look at directly preceding instruction, skipping bitcasts and lifetime
- // markers.
+ // Look at directly preceding instruction, skipping bitcasts, lifetime
+ // markers, and fake uses and their operands.
+ const llvm::Instruction *LoadIntoFakeUse = nullptr;
for (llvm::Instruction &I : make_range(IP->rbegin(), IP->rend())) {
+ // Ignore instructions that are just loads for fake uses; the load should
+ // immediately precede the fake use, so we only need to remember the
+ // operand for the last fake use seen.
+ if (LoadIntoFakeUse == &I)
+ continue;
if (isa<llvm::BitCastInst>(&I))
continue;
- if (auto *II = dyn_cast<llvm::IntrinsicInst>(&I))
+ if (auto *II = dyn_cast<llvm::IntrinsicInst>(&I)) {
if (II->getIntrinsicID() == llvm::Intrinsic::lifetime_end)
continue;
+ if (II->getIntrinsicID() == llvm::Intrinsic::fake_use) {
+ LoadIntoFakeUse = dyn_cast<llvm::Instruction>(II->getArgOperand(0));
+ continue;
+ }
+ }
return GetStoreIfValid(&I);
}
return nullptr;
diff --git a/clang/lib/CodeGen/CGCleanup.cpp b/clang/lib/CodeGen/CGCleanup.cpp
index 5d253c92a38a81..82532e182bebbd 100644
--- a/clang/lib/CodeGen/CGCleanup.cpp
+++ b/clang/lib/CodeGen/CGCleanup.cpp
@@ -112,11 +112,11 @@ void EHScopeStack::deallocate(size_t Size) {
StartOfData += llvm::alignTo(Size, ScopeStackAlignment);
}
-bool EHScopeStack::containsOnlyLifetimeMarkers(
+bool EHScopeStack::containsOnlyNoopCleanups(
EHScopeStack::stable_iterator Old) const {
for (EHScopeStack::iterator it = begin(); stabilize(it) != Old; it++) {
EHCleanupScope *cleanup = dyn_cast<EHCleanupScope>(&*it);
- if (!cleanup || !cleanup->isLifetimeMarker())
+ if (!cleanup || !(cleanup->isLifetimeMarker() || cleanup->isFakeUse()))
return false;
}
@@ -154,6 +154,7 @@ void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) {
bool IsNormalCleanup = Kind & NormalCleanup;
bool IsEHCleanup = Kind & EHCleanup;
bool IsLifetimeMarker = Kind & LifetimeMarker;
+ bool IsFakeUse = Kind & FakeUse;
// Per C++ [except.terminate], it is implementation-defined whether none,
// some, or all cleanups are called before std::terminate. Thus, when
@@ -176,6 +177,8 @@ void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) {
InnermostEHScope = stable_begin();
if (IsLifetimeMarker)
Scope->setLifetimeMarker();
+ if (IsFakeUse)
+ Scope->setFakeUse();
// With Windows -EHa, Invoke llvm.seh.scope.begin() for EHCleanup
// If exceptions are disabled/ignored and SEH is not in use, then there is no
diff --git a/clang/lib/CodeGen/CGCleanup.h b/clang/lib/CodeGen/CGCleanup.h
index c73c97146abc4d..ba78e5478ac373 100644
--- a/clang/lib/CodeGen/CGCleanup.h
+++ b/clang/lib/CodeGen/CGCleanup.h
@@ -87,6 +87,10 @@ class EHScope {
LLVM_PREFERRED_TYPE(bool)
unsigned IsLifetimeMarker : 1;
+ /// Whether this cleanup is a fake use
+ LLVM_PREFERRED_TYPE(bool)
+ unsigned IsFakeUse : 1;
+
/// Whether the normal cleanup should test the activation flag.
LLVM_PREFERRED_TYPE(bool)
unsigned TestFlagInNormalCleanup : 1;
@@ -352,6 +356,7 @@ class alignas(8) EHCleanupScope : public EHScope {
CleanupBits.IsEHCleanup = isEH;
CleanupBits.IsActive = true;
CleanupBits.IsLifetimeMarker = false;
+ CleanupBits.IsFakeUse = false;
CleanupBits.TestFlagInNormalCleanup = false;
CleanupBits.TestFlagInEHCleanup = false;
CleanupBits.CleanupSize = cleanupSize;
@@ -384,6 +389,9 @@ class alignas(8) EHCleanupScope : public EHScope {
bool isLifetimeMarker() const { return CleanupBits.IsLifetimeMarker; }
void setLifetimeMarker() { CleanupBits.IsLifetimeMarker = true; }
+ bool isFakeUse() const { return CleanupBits.IsFakeUse; }
+ void setFakeUse() { CleanupBits.IsFakeUse = true; }
+
bool hasActiveFlag() const { return ActiveFlag.isValid(); }
Address getActiveFlag() const {
return ActiveFlag;
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 563f728e29d781..7fdf18f3ca2e7b 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -1353,6 +1353,14 @@ void CodeGenFunction::EmitLifetimeEnd(llvm::Value *Size, llvm::Value *Addr) {
C->setDoesNotThrow();
}
+void CodeGenFunction::EmitFakeUse(Address Addr) {
+ auto NL = ApplyDebugLocation::CreateEmpty(*this);
+ llvm::Value *V = Builder.CreateLoad(Addr, "fake.use");
+ llvm::CallInst *C = Builder.CreateCall(CGM.getLLVMFakeUseFn(), {V});
+ C->setDoesNotThrow();
+ C->setTailCallKind(llvm::CallInst::TCK_NoTail);
+}
+
void CodeGenFunction::EmitAndRegisterVariableArrayDimensions(
CGDebugInfo *DI, const VarDecl &D, bool EmitDebugInfo) {
// For each dimension stores its QualType and corresponding
@@ -1412,6 +1420,39 @@ void CodeGenFunction::EmitAndRegisterVariableArrayDimensions(
}
}
+/// Return the maximum size of an aggregate for which we generate a fake use
+/// intrinsic when -fextend-lifetimes is in effect.
+static uint64_t maxFakeUseAggregateSize(const ASTContext &C) {
+ return 4 * C.getTypeSize(C.UnsignedIntTy);
+}
+
+// Helper function to determine whether a variable's or parameter's lifetime
+// should be extended.
+static bool extendLifetime(const ASTContext &Context, const Decl *FuncDecl,
+ const VarDecl &D,
+ ImplicitParamDecl *CXXABIThisDecl) {
+ // When we're not inside a valid function it is unlikely that any
+ // lifetime extension is useful.
+ if (!FuncDecl)
+ return false;
+ if (FuncDecl->isImplicit())
+ return false;
+ // Do not extend compiler-created variables except for the this pointer.
+ if (D.isImplicit() && &D != CXXABIThisDecl)
+ return false;
+ QualType Ty = D.getType();
+ // No need to extend volatiles, they have a memory location.
+ if (Ty.isVolatileQualified())
+ return false;
+ // Don't extend variables that exceed a certain size.
+ if (Context.getTypeSize(Ty) > maxFakeUseAggregateSize(Context))
+ return false;
+ // Do not extend variables in nodebug functions.
+ if (FuncDecl->hasAttr<NoDebugAttr>())
+ return false;
+ return true;
+}
+
/// EmitAutoVarAlloca - Emit the alloca and debug information for a
/// local variable. Does not emit initialization or destruction.
CodeGenFunction::AutoVarEmission
@@ -1664,6 +1705,17 @@ CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
emission.getOriginalAllocatedAddress(),
emission.getSizeForLifetimeMarkers());
+ // Analogous to lifetime markers, we use a 'cleanup' to emit fake.use
+ // calls for local variables. We are exempting volatile variables and
+ // non-scalars larger than 4 times the size of an unsigned int (32 bytes).
+ // Larger non-scalars are often allocated in memory and may create unnecessary
+ // overhead.
+ if (CGM.getCodeGenOpts().ExtendLifetimes) {
+ if (extendLifetime(getContext(), CurCodeDecl, D, CXXABIThisDecl))
+ EHStack.pushCleanup<FakeUse>(NormalFakeUse,
+ emission.getAllocatedAddress());
+ }
+
return emission;
}
@@ -2523,6 +2575,14 @@ llvm::Function *CodeGenModule::getLLVMLifetimeEndFn() {
return LifetimeEndFn;
}
+/// Lazily declare the @llvm.fake.use intrinsic.
+llvm::Function *CodeGenModule::getLLVMFakeUseFn() {
+ if (!FakeUseFn)
+ FakeUseFn = llvm::Intrinsic::getDeclaration(&getModule(),
+ llvm::Intrinsic::fake_use);
+ return FakeUseFn;
+}
+
namespace {
/// A cleanup to perform a release of an object at the end of a
/// function. This is used to balance out the incoming +1 of a
@@ -2716,6 +2776,15 @@ void CodeGenFunction::EmitParmDecl(const VarDecl &D, ParamValue Arg,
setAddrOfLocalVar(&D, DeclPtr);
+ // Push a FakeUse 'cleanup' object onto the EHStack for the parameter,
+ // which may be the 'this' pointer. This causes the emission of a fake.use
+ // call with the parameter as argument at the end of the function.
+ if (CGM.getCodeGenOpts().ExtendLifetimes ||
+ (CGM.getCodeGenOpts().ExtendThisPtr && &D == CXXABIThisDecl)) {
+ if (extendLifetime(getContext(), CurCodeDecl, D, CXXABIThisDecl))
+ EHStack.pushCleanup<FakeUse>(NormalFakeUse, DeclPtr);
+ }
+
// Emit debug info for param declarations in non-thunk functions.
if (CGDebugInfo *DI = getDebugInfo()) {
if (CGM.getCodeGenOpts().hasReducedDebugInfo() && !CurFuncIsThunk &&
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index eda96f3e352ce3..630a9c8db95fe5 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -403,9 +403,9 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
// important to do this before we enter the return block or return
// edges will be *really* confused.
bool HasCleanups = EHStack.stable_begin() != PrologueCleanupDepth;
- bool HasOnlyLifetimeMarkers =
- HasCleanups && EHStack.containsOnlyLifetimeMarkers(PrologueCleanupDepth);
- bool EmitRetDbgLoc = !HasCleanups || HasOnlyLifetimeMarkers;
+ bool HasOnlyNoopCleanups =
+ HasCleanups && EHStack.containsOnlyNoopCleanups(PrologueCleanupDepth);
+ bool EmitRetDbgLoc = !HasCleanups || HasOnlyNoopCleanups;
std::optional<ApplyDebugLocation> OAL;
if (HasCleanups) {
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 3e2abbd9bc1094..1525eb0f09b6e5 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -718,6 +718,20 @@ class CodeGenFunction : public CodeGenTypeCache {
}
};
+ // We are using objects of this 'cleanup' class to emit fake.use calls
+ // for -fextend-lifetimes and -fextend-this-ptr. They are placed at the end of
+ // a variable's scope analogous to lifetime markers.
+ class FakeUse final : public EHScopeStack::Cleanup {
+ Address Addr;
+
+ public:
+ FakeUse(Address addr) : Addr(addr) {}
+
+ void Emit(CodeGenFunction &CGF, Flags flags) override {
+ CGF.EmitFakeUse(Addr);
+ }
+ };
+
/// Header for data within LifetimeExtendedCleanupStack.
struct LifetimeExtendedCleanupHeader {
/// The size of the following cleanup object.
@@ -4975,6 +4989,8 @@ class CodeGenFunction : public CodeGenTypeCache {
RValue EmitAtomicExpr(AtomicExpr *E);
+ void EmitFakeUse(Address Addr);
+
//===--------------------------------------------------------------------===//
// Annotations Emission
//===--------------------------------------------------------------------===//
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index c58bb88035ca8a..71198134f17413 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -601,6 +601,9 @@ class CodeGenModule : public CodeGenTypeCache {
/// void @llvm.lifetime.end(i64 %size, i8* nocapture <ptr>)
llvm::Function *LifetimeEndFn = nullptr;
+ /// void @llvm.fake.use(...)
+ llvm::Function *FakeUseFn = nullptr;
+
std::unique_ptr<SanitizerMetadata> SanitizerMD;
llvm::MapVector<const Decl *, bool> DeferredEmptyCoverageMappingDecls;
@@ -1268,6 +1271,7 @@ class CodeGenModule : public CodeGenTypeCache {
llvm::Function *getLLVMLifetimeStartFn();
llvm::Function *getLLVMLifetimeEndFn();
+ llvm::Function *getLLVMFakeUseFn();
// Make sure that this type is translated.
void UpdateCompletedType(const TagDecl *TD);
diff --git a/clang/lib/CodeGen/EHScopeStack.h b/clang/lib/CodeGen/EHScopeStack.h
index 0c667e80bb6d8c..ed11dc2bb05d73 100644
--- a/clang/lib/CodeGen/EHScopeStack.h
+++ b/clang/lib/CodeGen/EHScopeStack.h
@@ -87,6 +87,11 @@ enum CleanupKind : unsigned {
LifetimeMarker = 0x8,
NormalEHLifetimeMarker = LifetimeMarker | NormalAndEHCleanup,
+
+ // FakeUse needs to be recognized as a special cleanup similar to lifetime
+ // markers chiefly to be ignored in most contexts.
+ FakeUse = 0x10,
+ NormalFakeUse = FakeUse | NormalCleanup,
};
/// A stack of scopes which respond to exceptions, including cleanups
@@ -352,8 +357,8 @@ class EHScopeStack {
void popTerminate();
// Returns true iff the current scope is either empty or contains only
- // lifetime markers, i.e. no real cleanup code
- bool containsOnlyLifetimeMarkers(stable_iterator Old) const;
+ // noop cleanups, i.e. lifetime markers and fake uses.
+ bool containsOnlyNoopCleanups(stable_iterator Old) const;
/// Determines whether the exception-scopes stack is empty.
bool empty() const { return StartOfData == EndOfBuffer; }
diff --git a/clang/test/CodeGen/extend-liveness1.c b/clang/test/CodeGen/extend-liveness1.c
new file mode 100644
index 00000000000000..ef2d00eb6be312
--- /dev/null
+++ b/clang/test/CodeGen/extend-liveness1.c
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 %s -O2 -emit-llvm -fextend-lifetimes -o - | FileCheck %s
+// Check that fake use calls are emitted at the correct locations, i.e.
+// at the end of lexical blocks and at the end of the function.
+
+extern int use(int);
+int glob1;
+int glob2;
+float globf;
+
+int foo(int i) {
+ // CHECK: define{{.*}}foo
+ if (i < 4) {
+ int j = i * 3;
+ if (glob1 > 3) {
+ float f = globf;
+ // CHECK: [[SSAVAL:%[a-z0-9]*]] = load float{{.*}}globf
+ j = f;
+ glob2 = j;
+ // CHECK: store{{.*}}glob2
+ // CHECK-NEXT: call void (...) @llvm.fake.use(float [[SSAVAL]])
+ }
+ glob1 = j;
+ // CHECK: store{{.*}}glob1
+ // CHECK-NEXT: call void (...) @llvm.fake.use(i32 %j.
+ }
+ // CHECK: call void (...) @llvm.fake.use(i32 %i)
+ // CHECK-NEXT: ret
+ return 4;
+}
diff --git a/clang/test/CodeGen/extend-liveness2.cpp b/clang/test/CodeGen/extend-liveness2.cpp
new file mode 100644
index 00000000000000..119c783c634806
--- /dev/null
+++ b/clang/test/CodeGen/extend-liveness2.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 %s -O2 -emit-llvm -fextend-lifetimes -fcxx-exceptions -fexceptions -o - | FileCheck %s
+// REQUIRES: x86-registered-target
+// This test checks that the fake_use concept works with exception handling and that we
+// can handle the __int128 data type.
+
+class A {
+public:
+ A(int i) : m_i(i) {}
+ void func(__int128 i128);
+
+ int m_i;
+};
+
+extern int bar();
+extern void foo();
+int glob;
+
+void A::func(__int128 i128) {
+ int j = 4;
+ try {
+ int k = bar();
+ foo();
+ // CHECK: [[SSAVAL:%[a-z0-9]*]] = invoke{{.*}}bar
+ glob = 0;
+ // CHECK: store{{.*}}glob
+ // CHECK-NEXT: call void (...) @llvm.fake.use(i32 [[SSAVAL]])
+ } catch (...) {
+ foo();
+ }
+ // CHECK-LABEL: try.cont:
+ // CHECK-DAG: call void (...) @llvm.fake.use({{.*%this}})
+ // CHECK-DAG: call void (...) @llvm.fake.use(i128 %i128.sroa.0.0.insert.insert)
+ // CHECK: ret void
+}
diff --git a/clang/test/CodeGen/fake-use-determinism.c b/clang/test/CodeGen/fake-use-determinism.c
new file mode 100644
index 00000000000000..d62efbb4efe7ee
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-determinism.c
@@ -0,0 +1,18 @@
+// RUN: %clang -S -O2 -emit-llvm -fextend-lifetimes %s -o - | FileCheck %s
+// REQUIRES: asserts
+//
+// We are checking that the fake.use calls for i, j and k appear
+// in a particular order. It is not the order itself that is important
+// but that it remains the same between different test runs.
+
+// CHECK: call {{.*}}void (...) @llvm.fake.use(i32 %k)
+// CHECK-NEXT: call {{.*}}void (...) @llvm.fake.use(i32 %j)
+// CHECK-NEXT: call {{.*}}void (...) @llvm.fake.use(i32 %i)
+
+extern void bar();
+void foo(int i, int j, int k)
+{
+ for (int l = 0; l < i; l++) {
+ bar();
+ }
+}
diff --git a/clang/test/CodeGen/fake-use-lambda.cpp b/clang/test/CodeGen/fake-use-lambda.cpp
new file mode 100644
index 00000000000000..fd4881b9bcd531
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-lambda.cpp
@@ -0,0 +1,43 @@
+// RUN: %clang_cc1 %s -triple=%itanium_abi_triple -O1 -emit-llvm -fextend-lifetimes -o - | FileCheck %s
+// Make sure we don't crash compiling a lambda that is not nested in a function.
+// We also check that fake uses are properly issued in lambdas.
+
+int glob;
+
+extern int foo();
+
+struct S {
+ static const int a;
+};
+
+const int S::a = [](int b) __attribute__((noinline)) {
+ return b * foo();
+}
+(glob);
+
+int func(int param) {
+ return ([=](int lambdaparm) __attribute__((noinline))->int {
+ int lambdalocal = lambdaparm * 2;
+ return lambdalocal;
+ }(glob));
+}
+
+// We are looking for the first lambda's call operator, which should contain
+// 2 fake uses, one for 'b' and one for its 'this' pointer (in that order).
+// The mangled function name contains a $_0, followed by 'cl'.
+// This lambda is an orphaned lambda, i.e. one without lexical parent.
+//
+// CHECK: define internal {{.+\"_Z.+\$_0.*cl.*\"}}
+// CHECK-NOT: ret
+// CHECK: fake.use(i32
+// CHECK-NOT: ret
+// CHECK: fake.use(ptr
+
+// The second lambda. We are looking for 3 fake uses.
+// CHECK: define internal {{.+\"_Z.+\$_0.*cl.*\"}}
+// CHECK-NOT: ret
+// CHECK: fake.use(i32
+// CHECK-NOT: ret
+// CHECK: fake.use(i32
+// CHECK-NOT: ret
+// CHECK: fake.use(ptr
diff --git a/clang/test/CodeGen/fake-use-landingpad.c b/clang/test/CodeGen/fake-use-landingpad.c
new file mode 100644
index 00000000000000..91526f29936146
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-landingpad.c
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 %s -O3 -emit-llvm -fextend-lifetimes -fexceptions -o - | FileCheck %s
+
+// Check that fake uses do not mistakenly cause a landing pad to be generated when
+// exceptions are enabled.
+
+extern void bar(int);
+void foo(int p) {
+ int a = 17;
+ bar(a);
+}
+
+// CHECK: define {{.*}} @foo
+// CHECK-NOT: personality
+// CHECK: entry:
+// CHECK: llvm.fake.use
+// CHECK-NOT: landingpad
diff --git a/clang/test/CodeGen/fake-use-noreturn.cpp b/clang/test/CodeGen/fake-use-noreturn.cpp
new file mode 100644
index 00000000000000..acfcb0ce90b5e4
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-noreturn.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang %s -S -emit-llvm -fextend-lifetimes -O2 -o - -fno-discard-value-names | FileCheck %s
+//
+// Check we can correctly produce fake uses for function-level variables even
+// when we have a return in a nested conditional and there is no code at the end
+// of the function.
+
+// CHECK-LABEL: define{{.*}}@_Z3fooi
+// CHECK: call{{.*}}llvm.fake.use(i32 %i)
+// CHECK-LABEL: define{{.*}}@_ZN1C3barEi
+// CHECK-DAG: call{{.*}}llvm.fake.use(i32 %i)
+// CHECK-DAG: call{{.*}}llvm.fake.use({{.*}}%this)
+
+void foo(int i) {
+ while (0)
+ if (1)
+ return;
+}
+
+class C {
+ void bar(int i);
+};
+
+void C::bar(int i) {
+ while (0)
+ if (1)
+ return;
+}
diff --git a/clang/test/CodeGen/fake-use-return-line.c b/clang/test/CodeGen/fake-use-return-line.c
new file mode 100644
index 00000000000000..0c4377058d6628
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-return-line.c
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -emit-llvm -O2 -debug-info-kind=limited -fextend-lifetimes -o - %s | FileCheck %s
+
+// Clang adjusts the line numbers of returns based on the line numbers of
+// dominating stores to %retval; we test that fake use intrinsics do not affect
+// this, and the return is given the correct line.
+
+// CHECK: define{{.*}}@main
+// CHECK: ret i32{{.*}}!dbg ![[MDINDEX:[0-9]*]]
+// CHECK: ![[MDINDEX]] = !DILocation(line: [[# @LINE + 5]]
+int main()
+{
+ volatile int a = 1;
+ int b = a + 2;
+ return b;
+}
diff --git a/clang/test/CodeGen/fake-use-sanitizer.cpp b/clang/test/CodeGen/fake-use-sanitizer.cpp
new file mode 100644
index 00000000000000..915924a2b31025
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-sanitizer.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 %s -O1 -emit-llvm -fextend-lifetimes -fsanitize=null -fsanitize-trap=null -o - | FileCheck --check-prefix TRAP %s
+// RUN: %clang_cc1 %s -O1 -emit-llvm -fextend-lifetimes -o - | FileCheck --check-prefix FAKEUSE %s
+
+// With -fextend-lifetimes the compiler generated a fake.use of a
+// reference variable at the end of the function, in the cleanup block. This prompted the
+// address sanitizer to verify that the variable has been allocated properly, even when
+// the function returns early.
+// We check that sanitizers are disabled for code generated for the benefit of fake.use
+// intrinsics, as well as that the fake.use is no longer generated in the cleanup block.
+// It should be generated in the block preceding the cleanup block instead.
+
+struct A { short s1, s2; };
+extern A& getA();
+
+void foo()
+{
+ auto& va = getA();
+ short s = va.s1 & ~va.s2;
+ if (s == 0)
+ return;
+
+ auto& vb = getA();
+}
+
+// TRAP: define{{.*}}foo
+// TRAP: [[COMPARE:%[^\s]*]] = icmp eq
+// TRAP-NOT: br i1 [[COMPARE]]{{.*}}trap
+// TRAP: br i1 [[COMPARE]]{{.*}}%if.end
+// TRAP-NOT: trap:
+// TRAP: if.end:
+// TRAP-NOT: call{{.*}}llvm.trap
+
+// FAKEUSE: if.end:
+// FAKEUSE-NEXT: [[CALL:%[^\s]*]] = {{.*}}call{{.*}}getA
+// FAKEUSE-NOT: br{{.*}}cleanup
+// FAKEUSE: call{{.*}}fake.use({{.*}}[[CALL]])
+// FAKEUSE: cleanup:
diff --git a/clang/test/CodeGen/fake-use-scalar.c b/clang/test/CodeGen/fake-use-scalar.c
new file mode 100644
index 00000000000000..e42216c4a7feda
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-scalar.c
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 %s -O2 -emit-llvm -fextend-lifetimes -o - | FileCheck %s
+// Make sure we don't generate fake.use for non-scalar variables.
+// Make sure we don't generate fake.use for volatile variables
+// and parameters even when they are scalar.
+
+struct A {
+ unsigned long t;
+ char c[1024];
+ unsigned char r[32];
+};
+
+
+int foo(volatile int param)
+{
+ struct A s;
+ volatile int vloc;
+ struct A v[128];
+ char c[33];
+ return 0;
+}
+
+// CHECK-NOT: fake.use
diff --git a/clang/test/CodeGen/fake-use-small-aggs.c b/clang/test/CodeGen/fake-use-small-aggs.c
new file mode 100644
index 00000000000000..236e3a08c533ef
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-small-aggs.c
@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 %s -O2 -emit-llvm -fextend-lifetimes -disable-llvm-passes -o - | FileCheck %s
+// Check that we generate a fake_use call for small aggregate types.
+
+// CHECK-DAG: %[[FAKEUSE1:[^ ]+]] = load{{.*}} %loc,
+// CHECK-DAG: call{{.*}}llvm.fake.use({{.*}}%[[FAKEUSE1]])
+// CHECK-DAG: %[[FAKEUSE2:[^ ]+]] = load{{.*}} %arr,
+// CHECK-DAG: call{{.*}}llvm.fake.use({{.*}}%[[FAKEUSE2]])
+// CHECK-DAG: %[[FAKEUSE3:[^ ]+]] = load{{.*}} %S,
+// CHECK-DAG: call{{.*}}llvm.fake.use({{.*}}%[[FAKEUSE3]])
+
+struct s {
+ int i;
+ int j;
+};
+
+extern void inita(int *);
+extern struct s inits();
+void foo(struct s S)
+{
+ int arr[4];
+ inita (arr);
+ struct s loc = inits();
+}
+
diff --git a/clang/test/CodeGen/fake-use-while.c b/clang/test/CodeGen/fake-use-while.c
new file mode 100644
index 00000000000000..6055a73636f6ce
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-while.c
@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 %s -O2 -emit-llvm -fextend-lifetimes -o - | FileCheck %s
+//
+// Check we don't assert when there is no more code after a while statement
+// and the body of the while statement ends in a return, i.e. no insertion point
+// is available.
+
+// CHECK: define{{.*}}foo
+// CHECK: call{{.*}}llvm.fake.use
+
+void foo() {
+ {
+ while (1) {
+ int ret;
+ if (1)
+ return;
+ }
+ }
+}
diff --git a/clang/test/CodeGen/fake-use.cpp b/clang/test/CodeGen/fake-use.cpp
new file mode 100644
index 00000000000000..b58ba3ea60c4a2
--- /dev/null
+++ b/clang/test/CodeGen/fake-use.cpp
@@ -0,0 +1,44 @@
+// RUN: %clang_cc1 %s -O2 -emit-llvm -fextend-this-ptr -o - | FileCheck %s
+// Check that we generate a fake_use call with the 'this' pointer as argument.
+// The call should appear after the call to bar().
+
+extern void bar();
+
+class v
+{
+public:
+ int x;
+ int y;
+ int z;
+ int w;
+
+ v(int a, int b, int c, int d) : x(a), y(b), z(c), w(d) {}
+};
+
+class w
+{
+public:
+ v test(int, int, int, int, int, int, int, int, int, int);
+ w(int in): a(in), b(1234) {}
+
+private:
+ int a;
+ int b;
+};
+
+v w::test(int q, int w, int e, int r, int t, int y, int u, int i, int o, int p)
+{
+// CHECK: define{{.*}}test
+ int res = q*w + e - r*t + y*u*i*o*p;
+ int res2 = (w + e + r + t + y + o)*(p*q);
+ int res3 = res + res2;
+ int res4 = q*e + t*y*i + p*e*w * 6 * 4 * 3;
+
+ v V(res, res2, res3, res4);
+
+ bar();
+// CHECK: call{{.*}}bar
+// CHECK: call void (...) @llvm.fake.use(ptr nonnull %this)
+ return V;
+// CHECK: ret
+}
diff --git a/clang/test/CodeGen/no-fake-use-O0.cpp b/clang/test/CodeGen/no-fake-use-O0.cpp
new file mode 100644
index 00000000000000..67b9fac9b1bffe
--- /dev/null
+++ b/clang/test/CodeGen/no-fake-use-O0.cpp
@@ -0,0 +1,50 @@
+// RUN: %clang_cc1 %s -O0 -emit-llvm -fextend-this-ptr -o - | FileCheck %s \
+// RUN: --implicit-check-not="call void (...) @llvm.fake.use"
+// RUN: %clang_cc1 %s -O0 -emit-llvm -fextend-lifetimes -o - | FileCheck %s \
+// RUN: --implicit-check-not="call void (...) @llvm.fake.use"
+// RUN: %clang_cc1 %s -O1 -emit-llvm -fextend-this-ptr -o - | FileCheck -check-prefix=OPT %s
+// RUN: %clang_cc1 %s -O1 -emit-llvm -fextend-lifetimes -o - | FileCheck -check-prefix=OPT %s
+// RUN: %clang_cc1 %s -Os -emit-llvm -fextend-this-ptr -o - | FileCheck -check-prefix=OPT %s
+// RUN: %clang_cc1 %s -Os -emit-llvm -fextend-lifetimes -o - | FileCheck -check-prefix=OPT %s
+// RUN: %clang_cc1 %s -Oz -emit-llvm -fextend-this-ptr -o - | FileCheck -check-prefix=OPT %s
+// RUN: %clang_cc1 %s -Oz -emit-llvm -fextend-lifetimes -o - | FileCheck -check-prefix=OPT %s
+// Check that we do not generate a fake_use call when we are not optimizing.
+
+extern void bar();
+
+class v
+{
+public:
+ int x;
+ int y;
+ int z;
+ int w;
+
+ v(int a, int b, int c, int d) : x(a), y(b), z(c), w(d) {}
+};
+
+class w
+{
+public:
+ v test(int, int, int, int, int, int, int, int, int, int);
+ w(int in): a(in), b(1234) {}
+
+private:
+ int a;
+ int b;
+};
+
+v w::test(int q, int w, int e, int r, int t, int y, int u, int i, int o, int p)
+{
+// CHECK: define{{.*}}test
+ int res = q*w + e - r*t + y*u*i*o*p;
+ int res2 = (w + e + r + t + y + o)*(p*q);
+ int res3 = res + res2;
+ int res4 = q*e + t*y*i + p*e*w * 6 * 4 * 3;
+
+ v V(res, res2, res3, res4);
+
+ bar();
+// OPT: call void (...) @llvm.fake.use
+ return V;
+}
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