[llvm] r268288 - Revert "[SimplifyCFG] Extend TryToSimplifyUncondBranchFromEmptyBlock for empty block including lifetime intrinsics"
Pete Cooper via llvm-commits
llvm-commits at lists.llvm.org
Tue May 3 09:35:46 PDT 2016
Thanks for reverting this. I think it also caused some LTO failures on green dragon, although I was still trying to reproduce them to make sure.
More detail is here (http://lab.llvm.org:8080/green/job/clang-stage2-configure-Rlto_build/8797/consoleFull), but were you seeing something like the following?
While deleting: i8* %
Use still stuck around after Def is destroyed: call void @llvm.lifetime.end(i64 24, i8* nonnull <badref>) #3, !dbg !4862
Use still stuck around after Def is destroyed: %.pre194 = load i8, i8* <badref>, align 8, !dbg !4799, !tbaa !4501
Use still stuck around after Def is destroyed: call void @llvm.memset.p0i8.i64(i8* <badref>, i8 0, i64 24, i32 8, i1 false) #3, !dbg !4783, !alias.scope !4791
Assertion failed: (use_empty() && "Uses remain when a value is destroyed!"), function ~Value, file /Users/buildslave/jenkins/sharedspace/phase1 at 2/llvm/lib/IR/Value.cpp, line 85.
Cheers,
Pete
> On May 2, 2016, at 12:43 PM, Reid Kleckner via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>
> Author: rnk
> Date: Mon May 2 14:43:22 2016
> New Revision: 268288
>
> URL: http://llvm.org/viewvc/llvm-project?rev=268288&view=rev
> Log:
> Revert "[SimplifyCFG] Extend TryToSimplifyUncondBranchFromEmptyBlock for empty block including lifetime intrinsics"
>
> This reverts commit r268254.
>
> This change causes assertion failures while building Chromium. Reduced
> test case coming soon.
>
> Modified:
> llvm/trunk/include/llvm/IR/BasicBlock.h
> llvm/trunk/lib/IR/BasicBlock.cpp
> llvm/trunk/lib/Transforms/Utils/Local.cpp
> llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
> llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll
>
> Modified: llvm/trunk/include/llvm/IR/BasicBlock.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/BasicBlock.h?rev=268288&r1=268287&r2=268288&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/IR/BasicBlock.h (original)
> +++ llvm/trunk/include/llvm/IR/BasicBlock.h Mon May 2 14:43:22 2016
> @@ -152,15 +152,6 @@ public:
> return const_cast<BasicBlock*>(this)->getFirstNonPHIOrDbgOrLifetime();
> }
>
> - /// \brief Returns a pointer to the first instruction in this block that is
> - /// not a PHINode, a debug intrinsic, a lifetime intrinsic, or a bitcast
> - /// instruction coupled with the following lifetime intrinsic.
> - Instruction *getFirstNonPHIOrDbgOrLifetimeOrBitCast();
> - const Instruction *getFirstNonPHIOrDbgOrLifetimeOrBitCast() const {
> - return const_cast<BasicBlock *>(this)
> - ->getFirstNonPHIOrDbgOrLifetimeOrBitCast();
> - }
> -
> /// \brief Returns an iterator to the first instruction in this block that is
> /// suitable for inserting a non-PHI instruction.
> ///
>
> Modified: llvm/trunk/lib/IR/BasicBlock.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/BasicBlock.cpp?rev=268288&r1=268287&r2=268288&view=diff
> ==============================================================================
> --- llvm/trunk/lib/IR/BasicBlock.cpp (original)
> +++ llvm/trunk/lib/IR/BasicBlock.cpp Mon May 2 14:43:22 2016
> @@ -206,30 +206,6 @@ Instruction* BasicBlock::getFirstNonPHIO
> return nullptr;
> }
>
> -Instruction *BasicBlock::getFirstNonPHIOrDbgOrLifetimeOrBitCast() {
> - for (Instruction &I : *this) {
> - if (isa<PHINode>(I) || isa<DbgInfoIntrinsic>(I))
> - continue;
> -
> - if (auto *II = dyn_cast<IntrinsicInst>(&I))
> - if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
> - II->getIntrinsicID() == Intrinsic::lifetime_end)
> - continue;
> -
> - if (auto *BCI = dyn_cast<BitCastInst>(&I)) {
> - if (auto *II = dyn_cast<IntrinsicInst>(++I.getIterator())) {
> - if ((II->getIntrinsicID() == Intrinsic::lifetime_start ||
> - II->getIntrinsicID() == Intrinsic::lifetime_end) &&
> - II->getOperand(1) == BCI) {
> - continue;
> - }
> - }
> - }
> - return &I;
> - }
> - return nullptr;
> -}
> -
> BasicBlock::iterator BasicBlock::getFirstInsertionPt() {
> Instruction *FirstNonPHI = getFirstNonPHI();
> if (!FirstNonPHI)
>
> Modified: llvm/trunk/lib/Transforms/Utils/Local.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Local.cpp?rev=268288&r1=268287&r2=268288&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/Local.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/Local.cpp Mon May 2 14:43:22 2016
> @@ -800,55 +800,6 @@ static void redirectValuesFromPredecesso
> replaceUndefValuesInPhi(PN, IncomingValues);
> }
>
> -/// Return true if BB has lifetime.end intrinsic.
> -///
> -static bool hasLifetime(BasicBlock *BB) {
> - for (auto &I : *BB) {
> - if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I)) {
> - if (II->getIntrinsicID() == Intrinsic::lifetime_end ||
> - II->getIntrinsicID() == Intrinsic::lifetime_start) {
> - return true;
> - }
> - }
> - }
> - return false;
> -}
> -
> -/// hoistLifetimeFromEmptyBlockToPred - Hoist lifetime.end intrinsics and
> -/// related bitcast instructions from BB to predecessors of BB.
> -///
> -static bool hoistLifetimeFromEmptyBlockToPred(BasicBlock *BB) {
> - // Check to see if all Preds have single successor and if not, we cannot
> - // hoist lifetime intrinsics because it would change semantics.
> - for (auto Pred : predecessors(BB))
> - if (!Pred->getSingleSuccessor())
> - return false;
> -
> - // Hoist all lifetime.end intrinsics and related bitcast instrunctions
> - // in BB to Preds.
> - for (auto &I : *BB) {
> - if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
> - if (II->getIntrinsicID() == Intrinsic::lifetime_end ||
> - II->getIntrinsicID() == Intrinsic::lifetime_start) {
> - for (auto Pred : predecessors(BB)) {
> - Instruction *NewII = I.clone();
> - NewII->insertBefore(Pred->getTerminator());
> -
> - if (I.getIterator() != BB->begin()) {
> - if (auto BC = dyn_cast<BitCastInst>(--I.getIterator())) {
> - assert(BC == I.getOperand(1));
> - auto NewBC = BC->clone();
> - NewBC->insertBefore(NewII);
> - NewII->setOperand(1, NewBC);
> - }
> - }
> - }
> - }
> - }
> - }
> - return true;
> -}
> -
> /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
> /// unconditional branch, and contains no instructions other than PHI nodes,
> /// potential side-effect free intrinsics and the branch. If possible,
> @@ -862,118 +813,74 @@ bool llvm::TryToSimplifyUncondBranchFrom
> BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
> if (BB == Succ) return false;
>
> - // If BB has lifetime.end intrinsics, simplify BB under more constraints.
> - if (hasLifetime(BB)) {
> - // Check to see if BB and its predecessors and successors have PHI.
> - if (isa<PHINode>(BB->begin()))
> - return false;
> -
> - for (auto Pred : predecessors(BB))
> - if (isa<PHINode>(Pred->begin()))
> - return false;
> -
> - for (auto Succ : successors(BB))
> - if (isa<PHINode>(Succ->begin()))
> - return false;
> -
> - if (Succ->getSinglePredecessor()) {
> - // BB is the only predecessor of Succ, so Succ will end up with exactly
> - // the same predecessors BB had.
> -
> - // Copy over any debug or lifetime instruction.
> - BB->getTerminator()->eraseFromParent();
> - Succ->getInstList().splice(Succ->getFirstNonPHI()->getIterator(),
> - BB->getInstList());
> -
> - } else {
> - // Unless BB is the only predecessor of Succ, hoist lifetime intrinsics
> - // to predecessors of BB and simplify BB.
> - if (!hoistLifetimeFromEmptyBlockToPred(BB)) {
> - return false;
> - }
> - }
> -
> - DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
> -
> - // Everything that jumped to BB now goes to Succ.
> - BB->replaceAllUsesWith(Succ);
> - if (!Succ->hasName())
> - Succ->takeName(BB);
> - BB->eraseFromParent(); // Delete the old basic block.
> - return true;
> - } else {
> - // Check to see if merging these blocks would cause conflicts for any of the
> - // phi nodes in BB or Succ. If not, we can safely merge.
> - if (!CanPropagatePredecessorsForPHIs(BB, Succ))
> - return false;
> -
> - // Check for cases where Succ has multiple predecessors and a PHI node in BB
> - // has uses which will not disappear when the PHI nodes are merged. It is
> - // possible to handle such cases, but difficult: it requires checking
> - // whether BB dominates Succ, which is non-trivial to calculate in the
> - // case where Succ has multiple predecessors. Also, it requires checking
> - // whether constructing the necessary self-referential PHI node doesn't
> - // introduce any conflicts; this isn't too difficult, but the previous code
> - // for doing this was incorrect.
> - //
> - // Note that if this check finds a live use, BB dominates Succ, so BB is
> - // something like a loop pre-header (or rarely, a part of an irreducible
> - // CFG);
> - // folding the branch isn't profitable in that case anyway.
> - if (!Succ->getSinglePredecessor()) {
> - BasicBlock::iterator BBI = BB->begin();
> - while (isa<PHINode>(*BBI)) {
> - for (Use &U : BBI->uses()) {
> - if (PHINode *PN = dyn_cast<PHINode>(U.getUser())) {
> - if (PN->getIncomingBlock(U) != BB)
> - return false;
> - } else {
> + // Check to see if merging these blocks would cause conflicts for any of the
> + // phi nodes in BB or Succ. If not, we can safely merge.
> + if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
> +
> + // Check for cases where Succ has multiple predecessors and a PHI node in BB
> + // has uses which will not disappear when the PHI nodes are merged. It is
> + // possible to handle such cases, but difficult: it requires checking whether
> + // BB dominates Succ, which is non-trivial to calculate in the case where
> + // Succ has multiple predecessors. Also, it requires checking whether
> + // constructing the necessary self-referential PHI node doesn't introduce any
> + // conflicts; this isn't too difficult, but the previous code for doing this
> + // was incorrect.
> + //
> + // Note that if this check finds a live use, BB dominates Succ, so BB is
> + // something like a loop pre-header (or rarely, a part of an irreducible CFG);
> + // folding the branch isn't profitable in that case anyway.
> + if (!Succ->getSinglePredecessor()) {
> + BasicBlock::iterator BBI = BB->begin();
> + while (isa<PHINode>(*BBI)) {
> + for (Use &U : BBI->uses()) {
> + if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) {
> + if (PN->getIncomingBlock(U) != BB)
> return false;
> - }
> + } else {
> + return false;
> }
> - ++BBI;
> }
> + ++BBI;
> }
> + }
>
> - DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
> + DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
>
> - if (isa<PHINode>(Succ->begin())) {
> - // If there is more than one pred of succ, and there are PHI nodes in
> - // the successor, then we need to add incoming edges for the PHI nodes
> - //
> - const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB));
> -
> - // Loop over all of the PHI nodes in the successor of BB.
> - for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
> - PHINode *PN = cast<PHINode>(I);
> + if (isa<PHINode>(Succ->begin())) {
> + // If there is more than one pred of succ, and there are PHI nodes in
> + // the successor, then we need to add incoming edges for the PHI nodes
> + //
> + const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB));
>
> - redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN);
> - }
> - }
> + // Loop over all of the PHI nodes in the successor of BB.
> + for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
> + PHINode *PN = cast<PHINode>(I);
>
> - if (Succ->getSinglePredecessor()) {
> - // BB is the only predecessor of Succ, so Succ will end up with exactly
> - // the same predecessors BB had.
> -
> - // Copy over any phi, debug or lifetime instruction.
> - BB->getTerminator()->eraseFromParent();
> - Succ->getInstList().splice(Succ->getFirstNonPHI()->getIterator(),
> - BB->getInstList());
> - } else {
> - while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
> - // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
> - assert(PN->use_empty() && "There shouldn't be any uses here!");
> - PN->eraseFromParent();
> - }
> + redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN);
> }
> + }
>
> - // Everything that jumped to BB now goes to Succ.
> - BB->replaceAllUsesWith(Succ);
> - if (!Succ->hasName())
> - Succ->takeName(BB);
> - BB->eraseFromParent(); // Delete the old basic block.
> - return true;
> + if (Succ->getSinglePredecessor()) {
> + // BB is the only predecessor of Succ, so Succ will end up with exactly
> + // the same predecessors BB had.
> +
> + // Copy over any phi, debug or lifetime instruction.
> + BB->getTerminator()->eraseFromParent();
> + Succ->getInstList().splice(Succ->getFirstNonPHI()->getIterator(),
> + BB->getInstList());
> + } else {
> + while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
> + // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
> + assert(PN->use_empty() && "There shouldn't be any uses here!");
> + PN->eraseFromParent();
> + }
> }
> +
> + // Everything that jumped to BB now goes to Succ.
> + BB->replaceAllUsesWith(Succ);
> + if (!Succ->hasName()) Succ->takeName(BB);
> + BB->eraseFromParent(); // Delete the old basic block.
> + return true;
> }
>
> /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
>
> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=268288&r1=268287&r2=268288&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Mon May 2 14:43:22 2016
> @@ -5056,15 +5056,14 @@ bool SimplifyCFGOpt::SimplifyUncondBranc
>
> if (SinkCommon && SinkThenElseCodeToEnd(BI))
> return true;
> - // If the Terminator is the only non-phi instruction except for bitcast
> - // instruction coupled with the following lifetime intrinsic, simplify the
> - // block. If LoopHeader is provided, check if the block is a loop header
> +
> + // If the Terminator is the only non-phi instruction, simplify the block.
> + // if LoopHeader is provided, check if the block is a loop header
> // (This is for early invocations before loop simplify and vectorization
> // to keep canonical loop forms for nested loops.
> // These blocks can be eliminated when the pass is invoked later
> // in the back-end.)
> - BasicBlock::iterator I =
> - BB->getFirstNonPHIOrDbgOrLifetimeOrBitCast()->getIterator();
> + BasicBlock::iterator I = BB->getFirstNonPHIOrDbg()->getIterator();
> if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() &&
> (!LoopHeaders || !LoopHeaders->count(BB)) &&
> TryToSimplifyUncondBranchFromEmptyBlock(BB))
>
> Modified: llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll?rev=268288&r1=268287&r2=268288&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll (original)
> +++ llvm/trunk/test/Transforms/SimplifyCFG/lifetime.ll Mon May 2 14:43:22 2016
> @@ -1,9 +1,6 @@
> ; RUN: opt < %s -simplifycfg -S | FileCheck %s
>
> ; Test that a lifetime intrinsic isn't removed because that would change semantics
> -; This case is that predecessor(s) of the target empty block (bb0) has multiple
> -; successors (bb0 and bb1) and its successor has multiple predecessors (entry and
> -; bb0).
>
> ; CHECK: foo
> ; CHECK: entry:
> @@ -30,232 +27,3 @@ declare void @f()
> declare void @llvm.lifetime.start(i64, i8* nocapture) nounwind
>
> declare void @llvm.lifetime.end(i64, i8* nocapture) nounwind
> -
> -; Test that empty block including lifetime intrinsic and not related bitcast
> -; instruction cannot be removed. It is because the block is not empty.
> -
> -; CHECK-LABEL: coo
> -; CHECK-LABEL: entry:
> -; CHECK-LABEL: if.then:
> -; CHECK-LABEL: if.else:
> -; CHECK-LABEL: if.end:
> -; CHECK-LABEL: bb:
> -; CHECK: ret
> -
> -define void @coo(i1 %x, i1 %y) {
> -entry:
> - %a = alloca i8, align 4
> - %b = alloca i32, align 4
> - br label %while.cond
> -
> -while.cond: ; preds = %if.end, %entry
> - br i1 %y, label %while.body, label %bb
> -
> -while.body: ; preds = %while.cond
> - call void @llvm.lifetime.start(i64 4, i8* %a)
> - %c = load i8, i8* %a, align 4
> - br i1 %x, label %if.then, label %if.else
> -
> -if.then: ; preds = %while.body
> - %d = add i8 %c, 1
> - br label %if.end
> -
> -if.else: ; preds = %while.body
> - %e = sub i8 %c, 1
> - br label %if.end
> -
> -if.end: ; preds = %if.else, %if.then
> - %f = bitcast i32* %b to i8*
> - call void @llvm.lifetime.end(i64 4, i8* %a)
> - br label %while.cond
> -
> -bb: ; preds = %while.cond
> - ret void
> -}
> -
> -; Test that empty block including lifetime intrinsic can be removed.
> -; Lifetime.end intrinsic is moved to predecessors because successor has
> -; multiple predecessors.
> -
> -; CHECK-LABEL: soo
> -; CHECK-LABEL: entry:
> -; CHECK-LABEL: if.then:
> -; CHECK-NEXT: %e
> -; CHECK-NEXT: call void @llvm.lifetime.end
> -; CHECK-LABEL: if.else:
> -; CHECK-NEXT: %g
> -; CHECK-NEXT: call void @llvm.lifetime.end
> -; CHECK-NEXT: br label %while.cond
> -; CHECK-NOT: if.end:
> -; CHECK: ret
> -
> -define void @soo(i1 %x, i1 %y) {
> -entry:
> - %a = alloca i8, align 4
> - br label %while.cond
> -
> -while.cond: ; preds = %if.end, %entry
> - br i1 %y, label %while.body, label %bb
> -
> -while.body: ; preds = %while.cond
> - call void @llvm.lifetime.start(i64 4, i8* %a)
> - %d = load i8, i8* %a, align 4
> - br i1 %x, label %if.then, label %if.else
> -
> -if.then: ; preds = %while.body
> - %e = add i8 %d, 1
> - br label %if.end
> -
> -if.else: ; preds = %while.body
> - %g = sub i8 %d, 1
> - br label %if.end
> -
> -if.end: ; preds = %if.else, %if.then
> - call void @llvm.lifetime.end(i64 4, i8* %a)
> - br label %while.cond
> -
> -bb: ; preds = %while.cond
> - ret void
> -}
> -
> -; Test that empty block including lifetime intrinsic and related bitcast
> -; instruction can be removed. Lifetime.end intrinsic and related bitcast
> -; instruction are moved to predecessors because successor has multiple
> -; predecessors.
> -
> -; CHECK-LABEL: boo
> -; CHECK-LABEL: entry:
> -; CHECK-LABEL: if.then:
> -; CHECK-NEXT: %e
> -; CHECK-NEXT: %[[T:[^ ]+]] = bitcast
> -; CHECK-NEXT: call void @llvm.lifetime.end(i64 4, i8* %[[T]])
> -; CHECK-LABEL: if.else:
> -; CHECK-NEXT: %g
> -; CHECK-NEXT: %[[B:[^ ]+]] = bitcast
> -; CHECK-NEXT: call void @llvm.lifetime.end(i64 4, i8* %[[B]])
> -; CHECK-NEXT: br label %while.cond
> -; CHECK-NOT: if.end:
> -; CHECK: ret
> -
> -define void @boo(i1 %x, i1 %y) {
> -entry:
> - %a = alloca i32, align 4
> - br label %while.cond
> -
> -while.cond: ; preds = %if.end, %entry
> - br i1 %y, label %while.body, label %bb
> -
> -while.body: ; preds = %while.cond
> - %b = bitcast i32* %a to i8*
> - call void @llvm.lifetime.start(i64 4, i8* %b)
> - %d = load i32, i32* %a, align 4
> - br i1 %x, label %if.then, label %if.else
> -
> -if.then: ; preds = %while.body
> - %e = add i32 %d, 1
> - br label %if.end
> -
> -if.else: ; preds = %while.body
> - %g = sub i32 %d, 1
> - br label %if.end
> -
> -if.end: ; preds = %if.else, %if.then
> - %c = bitcast i32* %a to i8*
> - call void @llvm.lifetime.end(i64 4, i8* %c)
> - br label %while.cond
> -
> -bb: ; preds = %while.cond
> - ret void
> -}
> -
> -; Test that empty block including lifetime intrinsic can be removed.
> -; Lifetime.start intrinsic is moved to predecessors because successor has
> -; multiple predecessors.
> -
> -; CHECK-LABEL: koo
> -; CHECK-LABEL: entry:
> -; CHECK-LABEL: if.then:
> -; CHECK-NEXT: call void @f
> -; CHECK-NEXT: call void @llvm.lifetime.start
> -; CHECK-LABEL: if.else:
> -; CHECK-NEXT: call void @g
> -; CHECK-NEXT: call void @llvm.lifetime.start
> -; CHECK-NEXT: br label %bb
> -; CHECK-NOT: if.end:
> -; CHECK: ret
> -
> -define void @koo(i1 %x, i1 %y, i1 %z) {
> -entry:
> - %a = alloca i8, align 4
> - br i1 %z, label %bb, label %bb0
> -
> -bb0: ; preds = %entry
> - br i1 %x, label %if.then, label %if.else
> -
> -if.then: ; preds = %bb0
> - call void @f()
> - br label %if.end
> -
> -if.else: ; preds = %bb0
> - call void @g()
> - br label %if.end
> -
> -if.end: ; preds = %if.else, %if.then
> - call void @llvm.lifetime.start(i64 4, i8* %a)
> - br label %bb
> -
> -bb: ; preds = %if.end, %entry
> - %d = load i8, i8* %a, align 4
> - call void @llvm.lifetime.end(i64 4, i8* %a)
> - ret void
> -}
> -
> -declare void @g()
> -
> -; Test that empty block including lifetime intrinsic and related bitcast
> -; instruction can be removed. Lifetime.start intrinsic and related bitcast
> -; instruction are moved to predecessors because successor has multiple
> -; predecessors.
> -
> -
> -; CHECK-LABEL: goo
> -; CHECK-LABEL: entry:
> -; CHECK-LABEL: if.then:
> -; CHECK-NEXT: call void @f
> -; CHECK-NEXT: %[[T:[^ ]+]] = bitcast
> -; CHECK-NEXT: call void @llvm.lifetime.start(i64 4, i8* %[[T]])
> -; CHECK-LABEL: if.else:
> -; CHECK-NEXT: call void @g
> -; CHECK-NEXT: %[[B:[^ ]+]] = bitcast
> -; CHECK-NEXT: call void @llvm.lifetime.start(i64 4, i8* %[[B]])
> -; CHECK-NEXT: br label %bb
> -; CHECK-NOT: if.end:
> -; CHECK: ret
> -
> -define void @goo(i1 %x, i1 %y, i1 %z) {
> -entry:
> - %a = alloca i32, align 4
> - br i1 %z, label %bb, label %bb0
> -
> -bb0: ; preds = %entry
> - br i1 %x, label %if.then, label %if.else
> -
> -if.then: ; preds = %bb0
> - call void @f()
> - br label %if.end
> -
> -if.else: ; preds = %bb0
> - call void @g()
> - br label %if.end
> -
> -if.end: ; preds = %if.else, %if.then
> - %b = bitcast i32* %a to i8*
> - call void @llvm.lifetime.start(i64 4, i8* %b)
> - br label %bb
> -
> -bb: ; preds = %if.end, %entry
> - %d = load i32, i32* %a, align 4
> - %c = bitcast i32* %a to i8*
> - call void @llvm.lifetime.end(i64 4, i8* %c)
> - ret void
> -}
>
>
> _______________________________________________
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