[llvm] [StackLifetime] Remove handling for lifetime size mismatch (PR #151965)
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Mon Aug 4 06:46:53 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-analysis
Author: Nikita Popov (nikic)
<details>
<summary>Changes</summary>
Split out from #<!-- -->150248:
Since #<!-- -->150944 the size passed to lifetime.start/end is considered meaningless. The lifetime always applies to the whole alloca.
Accordingly remove handling for size mismatch in the StackLifetime analysis.
---
Full diff: https://github.com/llvm/llvm-project/pull/151965.diff
4 Files Affected:
- (modified) llvm/include/llvm/Analysis/StackLifetime.h (-2)
- (modified) llvm/lib/Analysis/StackLifetime.cpp (+2-43)
- (modified) llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll (-21)
- (modified) llvm/test/Instrumentation/AddressSanitizer/lifetime-uar-uas.ll (+4-4)
``````````diff
diff --git a/llvm/include/llvm/Analysis/StackLifetime.h b/llvm/include/llvm/Analysis/StackLifetime.h
index 438407fb70561..13f837a22281a 100644
--- a/llvm/include/llvm/Analysis/StackLifetime.h
+++ b/llvm/include/llvm/Analysis/StackLifetime.h
@@ -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;
diff --git a/llvm/lib/Analysis/StackLifetime.cpp b/llvm/lib/Analysis/StackLifetime.cpp
index b3f999400f154..abe4985544e40 100644
--- a/llvm/lib/Analysis/StackLifetime.cpp
+++ b/llvm/lib/Analysis/StackLifetime.cpp
@@ -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;
@@ -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))
diff --git a/llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll b/llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll
index 7fa1cf47f06be..6c3dec9fadac7 100644
--- a/llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll
+++ b/llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll
@@ -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:
diff --git a/llvm/test/Instrumentation/AddressSanitizer/lifetime-uar-uas.ll b/llvm/test/Instrumentation/AddressSanitizer/lifetime-uar-uas.ll
index a40dad526a14d..3685d8d530bed 100644
--- a/llvm/test/Instrumentation/AddressSanitizer/lifetime-uar-uas.ll
+++ b/llvm/test/Instrumentation/AddressSanitizer/lifetime-uar-uas.ll
@@ -18,11 +18,11 @@ 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]+}}
@@ -30,7 +30,7 @@ entry:
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,
``````````
</details>
https://github.com/llvm/llvm-project/pull/151965
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