[llvm] f7907e9 - [TRE] allow TRE for non-capturing calls.
Alexey Lapshin via llvm-commits
llvm-commits at lists.llvm.org
Sat Jul 11 04:02:57 PDT 2020
Author: Alexey Lapshin
Date: 2020-07-11T14:01:48+03:00
New Revision: f7907e9d223d8484f9afd457ba614c2db2ae4743
URL: https://github.com/llvm/llvm-project/commit/f7907e9d223d8484f9afd457ba614c2db2ae4743
DIFF: https://github.com/llvm/llvm-project/commit/f7907e9d223d8484f9afd457ba614c2db2ae4743.diff
LOG: [TRE] allow TRE for non-capturing calls.
The current implementation of Tail Recursion Elimination has a very restricted
pre-requisite: AllCallsAreTailCalls. i.e. it requires that no function
call receives a pointer to local stack. Generally, function calls that
receive a pointer to local stack but do not capture it - should not
break TRE. This fix allows us to do TRE if it is proved that no pointer
to the local stack is escaped.
Reviewed by: efriedma
Differential Revision: https://reviews.llvm.org/D82085
Added:
llvm/test/Transforms/TailCallElim/tre-multiple-exits.ll
llvm/test/Transforms/TailCallElim/tre-noncapturing-alloca-calls.ll
Modified:
llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
llvm/test/Transforms/TailCallElim/basic.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 5bb1d54d7d12..bfd312a52ea5 100644
--- a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -81,6 +81,7 @@
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
#define DEBUG_TYPE "tailcallelim"
@@ -92,7 +93,10 @@ STATISTIC(NumAccumAdded, "Number of accumulators introduced");
/// Scan the specified function for alloca instructions.
/// If it contains any dynamic allocas, returns false.
static bool canTRE(Function &F) {
- // Because of PR962, we don't TRE dynamic allocas.
+ // TODO: We don't do TRE if dynamic allocas are used.
+ // Dynamic allocas allocate stack space which should be
+ // deallocated before new iteration started. That is
+ // currently not implemented.
return llvm::all_of(instructions(F), [](Instruction &I) {
auto *AI = dyn_cast<AllocaInst>(&I);
return !AI || AI->isStaticAlloca();
@@ -185,11 +189,9 @@ struct AllocaDerivedValueTracker {
};
}
-static bool markTails(Function &F, bool &AllCallsAreTailCalls,
- OptimizationRemarkEmitter *ORE) {
+static bool markTails(Function &F, OptimizationRemarkEmitter *ORE) {
if (F.callsFunctionThatReturnsTwice())
return false;
- AllCallsAreTailCalls = true;
// The local stack holds all alloca instructions and all byval arguments.
AllocaDerivedValueTracker Tracker;
@@ -272,11 +274,8 @@ static bool markTails(Function &F, bool &AllCallsAreTailCalls,
}
}
- if (!IsNoTail && Escaped == UNESCAPED && !Tracker.AllocaUsers.count(CI)) {
+ if (!IsNoTail && Escaped == UNESCAPED && !Tracker.AllocaUsers.count(CI))
DeferredTails.push_back(CI);
- } else {
- AllCallsAreTailCalls = false;
- }
}
for (auto *SuccBB : make_range(succ_begin(BB), succ_end(BB))) {
@@ -313,8 +312,6 @@ static bool markTails(Function &F, bool &AllCallsAreTailCalls,
LLVM_DEBUG(dbgs() << "Marked as tail call candidate: " << *CI << "\n");
CI->setTailCall();
Modified = true;
- } else {
- AllCallsAreTailCalls = false;
}
}
@@ -325,7 +322,16 @@ static bool markTails(Function &F, bool &AllCallsAreTailCalls,
/// instruction from after the call to before the call, assuming that all
/// instructions between the call and this instruction are movable.
///
-static bool canMoveAboveCall(Instruction *I, CallInst *CI, AliasAnalysis *AA) {
+static bool canMoveAboveCall(Instruction *I, CallInst *CI, AliasAnalysis *AA,
+ DenseMap<Value *, AllocaInst *> &AllocaForValue) {
+ if (isa<DbgInfoIntrinsic>(I))
+ return true;
+
+ if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
+ if (II->getIntrinsicID() == Intrinsic::lifetime_end &&
+ llvm::findAllocaForValue(II->getArgOperand(1), AllocaForValue))
+ return true;
+
// FIXME: We can move load/store/call/free instructions above the call if the
// call does not mod/ref the memory location being processed.
if (I->mayHaveSideEffects()) // This also handles volatile loads.
@@ -392,7 +398,6 @@ class TailRecursionEliminator {
// createTailRecurseLoopHeader the first time we find a call we can eliminate.
BasicBlock *HeaderBB = nullptr;
SmallVector<PHINode *, 8> ArgumentPHIs;
- bool RemovableCallsMustBeMarkedTail = false;
// PHI node to store our return value.
PHINode *RetPN = nullptr;
@@ -414,13 +419,15 @@ class TailRecursionEliminator {
// The instruction doing the accumulating.
Instruction *AccumulatorRecursionInstr = nullptr;
+ // The cache for <value, alloca instruction> pairs.
+ DenseMap<Value *, AllocaInst *> AllocaForValue;
+
TailRecursionEliminator(Function &F, const TargetTransformInfo *TTI,
AliasAnalysis *AA, OptimizationRemarkEmitter *ORE,
DomTreeUpdater &DTU)
: F(F), TTI(TTI), AA(AA), ORE(ORE), DTU(DTU) {}
- CallInst *findTRECandidate(Instruction *TI,
- bool CannotTailCallElimCallsMarkedTail);
+ CallInst *findTRECandidate(Instruction *TI);
void createTailRecurseLoopHeader(CallInst *CI);
@@ -428,11 +435,9 @@ class TailRecursionEliminator {
bool eliminateCall(CallInst *CI);
- bool foldReturnAndProcessPred(ReturnInst *Ret,
- bool CannotTailCallElimCallsMarkedTail);
+ bool foldReturnAndProcessPred(ReturnInst *Ret);
- bool processReturningBlock(ReturnInst *Ret,
- bool CannotTailCallElimCallsMarkedTail);
+ bool processReturningBlock(ReturnInst *Ret);
void cleanupAndFinalize();
@@ -443,8 +448,7 @@ class TailRecursionEliminator {
};
} // namespace
-CallInst *TailRecursionEliminator::findTRECandidate(
- Instruction *TI, bool CannotTailCallElimCallsMarkedTail) {
+CallInst *TailRecursionEliminator::findTRECandidate(Instruction *TI) {
BasicBlock *BB = TI->getParent();
if (&BB->front() == TI) // Make sure there is something before the terminator.
@@ -464,9 +468,9 @@ CallInst *TailRecursionEliminator::findTRECandidate(
--BBI;
}
- // If this call is marked as a tail call, and if there are dynamic allocas in
- // the function, we cannot perform this optimization.
- if (CI->isTailCall() && CannotTailCallElimCallsMarkedTail)
+ assert((!CI->isTailCall() || !CI->isNoTailCall()) &&
+ "Incompatible call site attributes(Tail,NoTail)");
+ if (!CI->isTailCall())
return nullptr;
// As a special case, detect code like this:
@@ -498,26 +502,13 @@ void TailRecursionEliminator::createTailRecurseLoopHeader(CallInst *CI) {
BranchInst *BI = BranchInst::Create(HeaderBB, NewEntry);
BI->setDebugLoc(CI->getDebugLoc());
- // If this function has self recursive calls in the tail position where some
- // are marked tail and some are not, only transform one flavor or another.
- // We have to choose whether we move allocas in the entry block to the new
- // entry block or not, so we can't make a good choice for both. We make this
- // decision here based on whether the first call we found to remove is
- // marked tail.
- // NOTE: We could do slightly better here in the case that the function has
- // no entry block allocas.
- RemovableCallsMustBeMarkedTail = CI->isTailCall();
-
- // If this tail call is marked 'tail' and if there are any allocas in the
- // entry block, move them up to the new entry block.
- if (RemovableCallsMustBeMarkedTail)
- // Move all fixed sized allocas from HeaderBB to NewEntry.
- for (BasicBlock::iterator OEBI = HeaderBB->begin(), E = HeaderBB->end(),
- NEBI = NewEntry->begin();
- OEBI != E;)
- if (AllocaInst *AI = dyn_cast<AllocaInst>(OEBI++))
- if (isa<ConstantInt>(AI->getArraySize()))
- AI->moveBefore(&*NEBI);
+ // Move all fixed sized allocas from HeaderBB to NewEntry.
+ for (BasicBlock::iterator OEBI = HeaderBB->begin(), E = HeaderBB->end(),
+ NEBI = NewEntry->begin();
+ OEBI != E;)
+ if (AllocaInst *AI = dyn_cast<AllocaInst>(OEBI++))
+ if (isa<ConstantInt>(AI->getArraySize()))
+ AI->moveBefore(&*NEBI);
// Now that we have created a new block, which jumps to the entry
// block, insert a PHI node for each argument of the function.
@@ -592,7 +583,7 @@ bool TailRecursionEliminator::eliminateCall(CallInst *CI) {
Instruction *AccRecInstr = nullptr;
BasicBlock::iterator BBI(CI);
for (++BBI; &*BBI != Ret; ++BBI) {
- if (canMoveAboveCall(&*BBI, CI, AA))
+ if (canMoveAboveCall(&*BBI, CI, AA, AllocaForValue))
continue;
// If we can't move the instruction above the call, it might be because it
@@ -620,9 +611,6 @@ bool TailRecursionEliminator::eliminateCall(CallInst *CI) {
if (!HeaderBB)
createTailRecurseLoopHeader(CI);
- if (RemovableCallsMustBeMarkedTail && !CI->isTailCall())
- return false;
-
// Ok, now that we know we have a pseudo-entry block WITH all of the
// required PHI nodes, add entries into the PHI node for the actual
// parameters passed into the tail-recursive call.
@@ -672,8 +660,7 @@ bool TailRecursionEliminator::eliminateCall(CallInst *CI) {
return true;
}
-bool TailRecursionEliminator::foldReturnAndProcessPred(
- ReturnInst *Ret, bool CannotTailCallElimCallsMarkedTail) {
+bool TailRecursionEliminator::foldReturnAndProcessPred(ReturnInst *Ret) {
BasicBlock *BB = Ret->getParent();
bool Change = false;
@@ -698,8 +685,7 @@ bool TailRecursionEliminator::foldReturnAndProcessPred(
while (!UncondBranchPreds.empty()) {
BranchInst *BI = UncondBranchPreds.pop_back_val();
BasicBlock *Pred = BI->getParent();
- if (CallInst *CI =
- findTRECandidate(BI, CannotTailCallElimCallsMarkedTail)) {
+ if (CallInst *CI = findTRECandidate(BI)) {
LLVM_DEBUG(dbgs() << "FOLDING: " << *BB
<< "INTO UNCOND BRANCH PRED: " << *Pred);
FoldReturnIntoUncondBranch(Ret, BB, Pred, &DTU);
@@ -720,9 +706,8 @@ bool TailRecursionEliminator::foldReturnAndProcessPred(
return Change;
}
-bool TailRecursionEliminator::processReturningBlock(
- ReturnInst *Ret, bool CannotTailCallElimCallsMarkedTail) {
- CallInst *CI = findTRECandidate(Ret, CannotTailCallElimCallsMarkedTail);
+bool TailRecursionEliminator::processReturningBlock(ReturnInst *Ret) {
+ CallInst *CI = findTRECandidate(Ret);
if (!CI)
return false;
@@ -810,35 +795,25 @@ bool TailRecursionEliminator::eliminate(Function &F,
return false;
bool MadeChange = false;
- bool AllCallsAreTailCalls = false;
- MadeChange |= markTails(F, AllCallsAreTailCalls, ORE);
- if (!AllCallsAreTailCalls)
- return MadeChange;
+ MadeChange |= markTails(F, ORE);
// If this function is a varargs function, we won't be able to PHI the args
// right, so don't even try to convert it...
if (F.getFunctionType()->isVarArg())
return MadeChange;
- // If false, we cannot perform TRE on tail calls marked with the 'tail'
- // attribute, because doing so would cause the stack size to increase (real
- // TRE would deallocate variable sized allocas, TRE doesn't).
- bool CanTRETailMarkedCall = canTRE(F);
+ if (!canTRE(F))
+ return MadeChange;
TailRecursionEliminator TRE(F, TTI, AA, ORE, DTU);
// Change any tail recursive calls to loops.
- //
- // FIXME: The code generator produces really bad code when an 'escaping
- // alloca' is changed from being a static alloca to being a dynamic alloca.
- // Until this is resolved, disable this transformation if that would ever
- // happen. This bug is PR962.
for (Function::iterator BBI = F.begin(), E = F.end(); BBI != E; /*in loop*/) {
BasicBlock *BB = &*BBI++; // foldReturnAndProcessPred may delete BB.
if (ReturnInst *Ret = dyn_cast<ReturnInst>(BB->getTerminator())) {
- bool Change = TRE.processReturningBlock(Ret, !CanTRETailMarkedCall);
+ bool Change = TRE.processReturningBlock(Ret);
if (!Change && BB->getFirstNonPHIOrDbg() == Ret)
- Change = TRE.foldReturnAndProcessPred(Ret, !CanTRETailMarkedCall);
+ Change = TRE.foldReturnAndProcessPred(Ret);
MadeChange |= Change;
}
}
diff --git a/llvm/test/Transforms/TailCallElim/basic.ll b/llvm/test/Transforms/TailCallElim/basic.ll
index 6116014a024b..669210da6314 100644
--- a/llvm/test/Transforms/TailCallElim/basic.ll
+++ b/llvm/test/Transforms/TailCallElim/basic.ll
@@ -12,15 +12,16 @@ define void @test0() {
ret void
}
-; PR615. Make sure that we do not move the alloca so that it interferes with the tail call.
+; Make sure that we do not do TRE if pointer to local stack
+; escapes through function call.
define i32 @test1() {
; CHECK: i32 @test1()
; CHECK-NEXT: alloca
%A = alloca i32 ; <i32*> [#uses=2]
store i32 5, i32* %A
call void @use(i32* %A)
-; CHECK: tail call i32 @test1
- %X = tail call i32 @test1() ; <i32> [#uses=1]
+; CHECK: call i32 @test1
+ %X = call i32 @test1() ; <i32> [#uses=1]
ret i32 %X
}
diff --git a/llvm/test/Transforms/TailCallElim/tre-multiple-exits.ll b/llvm/test/Transforms/TailCallElim/tre-multiple-exits.ll
new file mode 100644
index 000000000000..8f69087dd879
--- /dev/null
+++ b/llvm/test/Transforms/TailCallElim/tre-multiple-exits.ll
@@ -0,0 +1,125 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -tailcallelim -verify-dom-info -S | FileCheck %s
+
+; This test checks that TRE would be done for only one recursive call.
+; The test_multiple_exits function has three recursive calls.
+; First recursive call could not be eliminated because there is
+; escaped pointer to local variable. Second recursive call could
+; be eliminated. Thrid recursive call could not be eliminated since
+; this is not last call. Thus, test checks that TRE would be done
+; for only second recursive call.
+
+; IR for that test was generated from the following C++ source:
+;
+; void capture_arg (int*);
+; void test_multiple_exits (int param);
+; if (param >= 0 && param < 10) {
+; int temp;
+; capture_arg(&temp);
+; // TRE could not be done because pointer to local
+; // variable "temp" is escaped.
+; test_multiple_exits(param + 1);
+; } else if (param >=10 && param < 20) {
+; // TRE should be done.
+; test_multiple_exits(param + 1);
+; } else if (param >= 20 && param < 22) {
+; // TRE could not be done since recursive
+; // call is not last call.
+; test_multiple_exits(param + 1);
+; func();
+; }
+;
+; return;
+; }
+
+; Function Attrs: noinline optnone uwtable
+declare void @_Z11capture_argPi(i32* %param) #0
+
+; Function Attrs: noinline optnone uwtable
+declare void @_Z4funcv() #0
+
+; Function Attrs: noinline nounwind uwtable
+define dso_local void @_Z19test_multiple_exitsi(i32 %param) local_unnamed_addr #2 {
+; CHECK-LABEL: @_Z19test_multiple_exitsi(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TEMP:%.*]] = alloca i32, align 4
+; CHECK-NEXT: br label [[TAILRECURSE:%.*]]
+; CHECK: tailrecurse:
+; CHECK-NEXT: [[PARAM_TR:%.*]] = phi i32 [ [[PARAM:%.*]], [[ENTRY:%.*]] ], [ [[ADD6:%.*]], [[IF_THEN5:%.*]] ]
+; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[PARAM_TR]], 10
+; CHECK-NEXT: br i1 [[TMP0]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[TMP1:%.*]] = bitcast i32* [[TEMP]] to i8*
+; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[TMP1]]) #1
+; CHECK-NEXT: call void @_Z11capture_argPi(i32* nonnull [[TEMP]])
+; CHECK-NEXT: [[ADD:%.*]] = add nuw nsw i32 [[PARAM_TR]], 1
+; CHECK-NEXT: call void @_Z19test_multiple_exitsi(i32 [[ADD]])
+; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[TMP1]]) #1
+; CHECK-NEXT: br label [[IF_END14:%.*]]
+; CHECK: if.else:
+; CHECK-NEXT: [[PARAM_OFF:%.*]] = add i32 [[PARAM_TR]], -10
+; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i32 [[PARAM_OFF]], 10
+; CHECK-NEXT: br i1 [[TMP2]], label [[IF_THEN5]], label [[IF_ELSE7:%.*]]
+; CHECK: if.then5:
+; CHECK-NEXT: [[ADD6]] = add nuw nsw i32 [[PARAM_TR]], 1
+; CHECK-NEXT: br label [[TAILRECURSE]]
+; CHECK: if.else7:
+; CHECK-NEXT: [[TMP3:%.*]] = and i32 [[PARAM_TR]], -2
+; CHECK-NEXT: [[TMP4:%.*]] = icmp eq i32 [[TMP3]], 20
+; CHECK-NEXT: br i1 [[TMP4]], label [[IF_THEN11:%.*]], label [[IF_END14]]
+; CHECK: if.then11:
+; CHECK-NEXT: [[ADD12:%.*]] = add nsw i32 [[PARAM_TR]], 1
+; CHECK-NEXT: tail call void @_Z19test_multiple_exitsi(i32 [[ADD12]])
+; CHECK-NEXT: tail call void @_Z4funcv()
+; CHECK-NEXT: ret void
+; CHECK: if.end14:
+; CHECK-NEXT: ret void
+;
+entry:
+ %temp = alloca i32, align 4
+ %0 = icmp ult i32 %param, 10
+ br i1 %0, label %if.then, label %if.else
+
+if.then: ; preds = %entry
+ %1 = bitcast i32* %temp to i8*
+ call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %1) #2
+ call void @_Z11capture_argPi(i32* nonnull %temp)
+ %add = add nuw nsw i32 %param, 1
+ call void @_Z19test_multiple_exitsi(i32 %add)
+ call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %1) #2
+ br label %if.end14
+
+if.else: ; preds = %entry
+ %param.off = add i32 %param, -10
+ %2 = icmp ult i32 %param.off, 10
+ br i1 %2, label %if.then5, label %if.else7
+
+if.then5: ; preds = %if.else
+ %add6 = add nuw nsw i32 %param, 1
+ call void @_Z19test_multiple_exitsi(i32 %add6)
+ br label %if.end14
+
+if.else7: ; preds = %if.else
+ %3 = and i32 %param, -2
+ %4 = icmp eq i32 %3, 20
+ br i1 %4, label %if.then11, label %if.end14
+
+if.then11: ; preds = %if.else7
+ %add12 = add nsw i32 %param, 1
+ call void @_Z19test_multiple_exitsi(i32 %add12)
+ call void @_Z4funcv()
+ br label %if.end14
+
+if.end14: ; preds = %if.then5, %if.then11, %if.else7, %if.then
+ ret void
+}
+
+; Function Attrs: argmemonly nounwind willreturn
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #2
+
+; Function Attrs: argmemonly nounwind willreturn
+declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #2
+
+attributes #0 = { nofree noinline norecurse nounwind uwtable }
+attributes #1 = { nounwind uwtable }
+attributes #2 = { argmemonly nounwind willreturn }
diff --git a/llvm/test/Transforms/TailCallElim/tre-noncapturing-alloca-calls.ll b/llvm/test/Transforms/TailCallElim/tre-noncapturing-alloca-calls.ll
new file mode 100644
index 000000000000..2168437fc570
--- /dev/null
+++ b/llvm/test/Transforms/TailCallElim/tre-noncapturing-alloca-calls.ll
@@ -0,0 +1,74 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -tailcallelim -verify-dom-info -S | FileCheck %s
+
+; IR for that test was generated from the following C++ source:
+;
+;int count;
+;__attribute__((noinline)) void globalIncrement(const int* param) { count += *param; }
+;
+;void test(int recurseCount)
+;{
+; if (recurseCount == 0) return;
+; int temp = 10;
+; globalIncrement(&temp);
+; test(recurseCount - 1);
+;}
+;
+
+ at count = dso_local local_unnamed_addr global i32 0, align 4
+
+; Function Attrs: nofree noinline norecurse nounwind uwtable
+declare void @_Z15globalIncrementPKi(i32* nocapture readonly %param) #0
+
+; Test that TRE could be done for recursive tail routine containing
+; call to function receiving a pointer to local stack.
+
+; Function Attrs: nounwind uwtable
+define dso_local void @_Z4testi(i32 %recurseCount) local_unnamed_addr #1 {
+; CHECK-LABEL: @_Z4testi(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TEMP:%.*]] = alloca i32, align 4
+; CHECK-NEXT: br label [[TAILRECURSE:%.*]]
+; CHECK: tailrecurse:
+; CHECK-NEXT: [[RECURSECOUNT_TR:%.*]] = phi i32 [ [[RECURSECOUNT:%.*]], [[ENTRY:%.*]] ], [ [[SUB:%.*]], [[IF_END:%.*]] ]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[RECURSECOUNT_TR]], 0
+; CHECK-NEXT: br i1 [[CMP]], label [[RETURN:%.*]], label [[IF_END]]
+; CHECK: if.end:
+; CHECK-NEXT: [[TMP0:%.*]] = bitcast i32* [[TEMP]] to i8*
+; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[TMP0]])
+; CHECK-NEXT: store i32 10, i32* [[TEMP]], align 4
+; CHECK-NEXT: call void @_Z15globalIncrementPKi(i32* nonnull [[TEMP]])
+; CHECK-NEXT: [[SUB]] = add nsw i32 [[RECURSECOUNT_TR]], -1
+; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[TMP0]])
+; CHECK-NEXT: br label [[TAILRECURSE]]
+; CHECK: return:
+; CHECK-NEXT: ret void
+;
+entry:
+ %temp = alloca i32, align 4
+ %cmp = icmp eq i32 %recurseCount, 0
+ br i1 %cmp, label %return, label %if.end
+
+if.end: ; preds = %entry
+ %0 = bitcast i32* %temp to i8*
+ call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %0) #6
+ store i32 10, i32* %temp, align 4
+ call void @_Z15globalIncrementPKi(i32* nonnull %temp)
+ %sub = add nsw i32 %recurseCount, -1
+ call void @_Z4testi(i32 %sub)
+ call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %0) #6
+ br label %return
+
+return: ; preds = %entry, %if.end
+ ret void
+}
+
+; Function Attrs: argmemonly nounwind willreturn
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #2
+
+; Function Attrs: argmemonly nounwind willreturn
+declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #2
+
+attributes #0 = { nofree noinline norecurse nounwind uwtable }
+attributes #1 = { nounwind uwtable }
+attributes #2 = { argmemonly nounwind willreturn }
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