Skip to content

[StackLifetime] Remove handling for lifetime size mismatch #151965

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Aug 5, 2025
+6 −70
Merged

[StackLifetime] Remove handling for lifetime size mismatch #151965

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 0 additions & 2 deletions llvm/include/llvm/Analysis/StackLifetime.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -121,8 +121,6 @@ class StackLifetime {
DenseMap<const BasicBlock *, SmallVector<std::pair<unsigned, Marker>, 4>>
BBMarkers;

bool HasUnknownLifetimeStartOrEnd = false;

void dumpAllocas() const;
void dumpBlockLiveness() const;
void dumpLiveRanges() const;
Expand Down
45 changes: 2 additions & 43 deletions llvm/lib/Analysis/StackLifetime.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -59,47 +59,20 @@ bool StackLifetime::isAliveAfter(const AllocaInst *AI,
return getLiveRange(AI).test(InstNum);
}

// Returns unique alloca annotated by lifetime marker only if
// markers has the same size and points to the alloca start.
static const AllocaInst *findMatchingAlloca(const IntrinsicInst &II,
const DataLayout &DL) {
const AllocaInst *AI = dyn_cast<AllocaInst>(II.getArgOperand(1));
if (!AI)
return nullptr;

auto AllocaSize = AI->getAllocationSize(DL);
if (!AllocaSize)
return nullptr;

auto *Size = dyn_cast<ConstantInt>(II.getArgOperand(0));
if (!Size)
return nullptr;
int64_t LifetimeSize = Size->getSExtValue();

if (LifetimeSize != -1 && uint64_t(LifetimeSize) != *AllocaSize)
return nullptr;

return AI;
}

void StackLifetime::collectMarkers() {
InterestingAllocas.resize(NumAllocas);
DenseMap<const BasicBlock *, SmallDenseMap<const IntrinsicInst *, Marker>>
BBMarkerSet;

const DataLayout &DL = F.getDataLayout();

// Compute the set of start/end markers per basic block.
for (const BasicBlock *BB : depth_first(&F)) {
for (const Instruction &I : *BB) {
const IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
if (!II || !II->isLifetimeStartOrEnd())
continue;
const AllocaInst *AI = findMatchingAlloca(*II, DL);
if (!AI) {
HasUnknownLifetimeStartOrEnd = true;
const AllocaInst *AI = dyn_cast<AllocaInst>(II->getArgOperand(1));
if (!AI)
continue;
}
auto It = AllocaNumbering.find(AI);
if (It == AllocaNumbering.end())
continue;
Expand Down Expand Up @@ -328,20 +301,6 @@ StackLifetime::StackLifetime(const Function &F,
}

void StackLifetime::run() {
if (HasUnknownLifetimeStartOrEnd) {
// There is marker which we can't assign to a specific alloca, so we
// fallback to the most conservative results for the type.
switch (Type) {
case LivenessType::May:
LiveRanges.resize(NumAllocas, getFullLiveRange());
break;
case LivenessType::Must:
LiveRanges.resize(NumAllocas, LiveRange(Instructions.size()));
break;
}
return;
}

LiveRanges.resize(NumAllocas, LiveRange(Instructions.size()));
for (unsigned I = 0; I < NumAllocas; ++I)
if (!InterestingAllocas.test(I))
Expand Down
21 changes: 0 additions & 21 deletions llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -786,27 +786,6 @@ end:
ret void
}

define void @alloca_size() {
; CHECK-LABEL: define void @alloca_size
entry:
; CHECK: entry:
; MAY-NEXT: Alive: <x>
; MUST-NEXT: Alive: <>
%x = alloca [5 x i32], align 4

call void @llvm.lifetime.start.p0(i64 15, ptr %x)
; CHECK: call void @llvm.lifetime.start.p0(i64 15, ptr %x)
; MAY-NEXT: Alive: <x>
; MUST-NEXT: Alive: <>

call void @llvm.lifetime.end.p0(i64 15, ptr %x)
; CHECK: call void @llvm.lifetime.end.p0(i64 15, ptr %x)
; MAY-NEXT: Alive: <x>
; MUST-NEXT: Alive: <>

ret void
}

define void @multiple_start_end() {
; CHECK-LABEL: define void @multiple_start_end
entry:
Expand Down
8 changes: 4 additions & 4 deletions llvm/test/Instrumentation/AddressSanitizer/lifetime-uar-uas.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -18,19 +18,19 @@ entry:
%retval = alloca i32, align 4
%c = alloca [2 x i8], align 1

; Memory is poisoned in prologue: F1F1F1F104F3F8F2
; CHECK-UAS: store i64 -866676825215864335, ptr %{{[0-9]+}}
; Memory is poisoned in prologue: F1F1F1F1F8F3F3F3
; CHECK-UAS: store i64 -868082052615769615, ptr %{{[0-9]+}}
; CHECK-UAS-SS-NOT: store i64

call void @llvm.lifetime.start.p0(i64 1, ptr %c)
call void @llvm.lifetime.start.p0(i64 2, ptr %c)
; Memory is unpoisoned at llvm.lifetime.start: 01
; CHECK-UAS: store i8 2, ptr %{{[0-9]+}}

%ci = getelementptr inbounds [2 x i8], ptr %c, i64 0, i64 %i
store volatile i32 0, ptr %retval
store volatile i8 0, ptr %ci, align 1

call void @llvm.lifetime.end.p0(i64 1, ptr %c)
call void @llvm.lifetime.end.p0(i64 2, ptr %c)
; Memory is poisoned at llvm.lifetime.end: F8
; CHECK-UAS: store i8 -8, ptr %{{[0-9]+}}
; CHECK-UAS-SS-NOT: store i8 -8,
Expand Down