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[Coroutines] Part14: Handle coroutines with no suspend points.
Summary: If coroutine has no suspend points, remove heap allocation and turn a coroutine into a normal function. Also, if a pattern is detected that coroutine resumes or destroys itself prior to coro.suspend call, turn the suspend point into a simple jump to resume or cleanup label. This pattern occurs when coroutines are used to propagate errors in functions that return expected<T>. Reviewers: majnemer Subscribers: mehdi_amini, llvm-commits Differential Revision: https://reviews.llvm.org/D24408 llvm-svn: 282414
This commit is contained in:
Gor Nishanov
parent
0e859047b9
commit
5e19e9e23d
@ -80,6 +80,14 @@ class LLVM_LIBRARY_VISIBILITY CoroIdInst : public IntrinsicInst {
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enum { AlignArg, PromiseArg, CoroutineArg, InfoArg };
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public:
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IntrinsicInst *getCoroAlloc() {
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for (User *U : users())
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if (auto *II = dyn_cast<IntrinsicInst>(U))
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if (II->getIntrinsicID() == Intrinsic::coro_alloc)
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return II;
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return nullptr;
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}
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IntrinsicInst *getCoroBegin() {
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for (User *U : users())
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if (auto *II = dyn_cast<IntrinsicInst>(U))
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@ -361,14 +361,126 @@ static void postSplitCleanup(Function &F) {
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FPM.doFinalization();
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}
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// Coroutine has no suspend points. Remove heap allocation for the coroutine
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// frame if possible.
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static void handleNoSuspendCoroutine(CoroBeginInst *CoroBegin, Type *FrameTy) {
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auto *CoroId = CoroBegin->getId();
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auto *AllocInst = CoroId->getCoroAlloc();
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coro::replaceCoroFree(CoroId, /*Elide=*/AllocInst != nullptr);
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if (AllocInst) {
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IRBuilder<> Builder(AllocInst);
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// FIXME: Need to handle overaligned members.
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auto *Frame = Builder.CreateAlloca(FrameTy);
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auto *VFrame = Builder.CreateBitCast(Frame, Builder.getInt8PtrTy());
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AllocInst->replaceAllUsesWith(Builder.getFalse());
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AllocInst->eraseFromParent();
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CoroBegin->replaceAllUsesWith(VFrame);
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} else {
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CoroBegin->replaceAllUsesWith(CoroBegin->getMem());
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}
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CoroBegin->eraseFromParent();
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}
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// look for a very simple pattern
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// coro.save
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// no other calls
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// resume or destroy call
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// coro.suspend
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//
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// If there are other calls between coro.save and coro.suspend, they can
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// potentially resume or destroy the coroutine, so it is unsafe to eliminate a
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// suspend point.
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static bool simplifySuspendPoint(CoroSuspendInst *Suspend,
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CoroBeginInst *CoroBegin) {
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auto *Save = Suspend->getCoroSave();
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auto *BB = Suspend->getParent();
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if (BB != Save->getParent())
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return false;
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CallSite SingleCallSite;
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// Check that we have only one CallSite.
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for (Instruction *I = Save->getNextNode(); I != Suspend;
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I = I->getNextNode()) {
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if (isa<CoroFrameInst>(I))
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continue;
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if (isa<CoroSubFnInst>(I))
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continue;
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if (CallSite CS = CallSite(I)) {
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if (SingleCallSite)
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return false;
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else
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SingleCallSite = CS;
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}
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}
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auto *CallInstr = SingleCallSite.getInstruction();
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if (!CallInstr)
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return false;
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auto *Callee = SingleCallSite.getCalledValue()->stripPointerCasts();
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// See if the callsite is for resumption or destruction of the coroutine.
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auto *SubFn = dyn_cast<CoroSubFnInst>(Callee);
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if (!SubFn)
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return false;
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// Does not refer to the current coroutine, we cannot do anything with it.
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if (SubFn->getFrame() != CoroBegin)
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return false;
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// Replace llvm.coro.suspend with the value that results in resumption over
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// the resume or cleanup path.
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Suspend->replaceAllUsesWith(SubFn->getRawIndex());
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Suspend->eraseFromParent();
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Save->eraseFromParent();
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// No longer need a call to coro.resume or coro.destroy.
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CallInstr->eraseFromParent();
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if (SubFn->user_empty())
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SubFn->eraseFromParent();
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return true;
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}
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// Remove suspend points that are simplified.
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static void simplifySuspendPoints(coro::Shape &Shape) {
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auto &S = Shape.CoroSuspends;
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size_t I = 0, N = S.size();
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if (N == 0)
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return;
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for (;;) {
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if (simplifySuspendPoint(S[I], Shape.CoroBegin)) {
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if (--N == I)
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break;
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std::swap(S[I], S[N]);
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continue;
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}
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if (++I == N)
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break;
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}
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S.resize(N);
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}
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static void splitCoroutine(Function &F, CallGraph &CG, CallGraphSCC &SCC) {
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coro::Shape Shape(F);
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if (!Shape.CoroBegin)
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return;
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simplifySuspendPoints(Shape);
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buildCoroutineFrame(F, Shape);
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replaceFrameSize(Shape);
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// If there are no suspend points, no split required, just remove
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// the allocation and deallocation blocks, they are not needed.
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if (Shape.CoroSuspends.empty()) {
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handleNoSuspendCoroutine(Shape.CoroBegin, Shape.FrameTy);
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removeCoroEnds(Shape);
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postSplitCleanup(F);
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coro::updateCallGraph(F, {}, CG, SCC);
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return;
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}
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auto *ResumeEntry = createResumeEntryBlock(F, Shape);
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auto ResumeClone = createClone(F, ".resume", Shape, ResumeEntry, 0);
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auto DestroyClone = createClone(F, ".destroy", Shape, ResumeEntry, 1);
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189
test/Transforms/Coroutines/no-suspend.ll
Normal file
189
test/Transforms/Coroutines/no-suspend.ll
Normal file
@ -0,0 +1,189 @@
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; Test no suspend coroutines
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; RUN: opt < %s -O2 -enable-coroutines -S | FileCheck %s
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; Coroutine with no-suspends will turn into:
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;
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; CHECK-LABEL: define void @no_suspends(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call void @print(i32 %n)
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; CHECK-NEXT: ret void
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;
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define void @no_suspends(i32 %n) {
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entry:
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%id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
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%need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
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br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
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dyn.alloc:
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%size = call i32 @llvm.coro.size.i32()
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%alloc = call i8* @malloc(i32 %size)
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br label %coro.begin
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coro.begin:
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%phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
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%hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
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br label %body
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body:
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call void @print(i32 %n)
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br label %cleanup
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cleanup:
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%mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
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%need.dyn.free = icmp ne i8* %mem, null
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br i1 %need.dyn.free, label %dyn.free, label %suspend
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dyn.free:
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call void @free(i8* %mem)
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br label %suspend
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suspend:
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call void @llvm.coro.end(i8* %hdl, i1 false)
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ret void
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}
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; SimplifySuspendPoint will detect that coro.resume resumes itself and will
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; replace suspend with a jump to %resume label turning it into no-suspend
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; coroutine.
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;
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; CHECK-LABEL: define void @simplify_resume(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call void @print(i32 0)
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; CHECK-NEXT: ret void
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;
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define void @simplify_resume() {
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entry:
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%id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
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%need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
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br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
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dyn.alloc:
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%size = call i32 @llvm.coro.size.i32()
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%alloc = call i8* @malloc(i32 %size)
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br label %coro.begin
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coro.begin:
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%phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
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%hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
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br label %body
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body:
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%save = call token @llvm.coro.save(i8* %hdl)
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call void @llvm.coro.resume(i8* %hdl)
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%0 = call i8 @llvm.coro.suspend(token %save, i1 false)
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switch i8 %0, label %suspend [i8 0, label %resume
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i8 1, label %pre.cleanup]
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resume:
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call void @print(i32 0)
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br label %cleanup
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pre.cleanup:
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call void @print(i32 1)
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br label %cleanup
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cleanup:
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%mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
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call void @free(i8* %mem)
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br label %suspend
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suspend:
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call void @llvm.coro.end(i8* %hdl, i1 false)
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ret void
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}
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; SimplifySuspendPoint will detect that coroutine destroys itself and will
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; replace suspend with a jump to %cleanup label turning it into no-suspend
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; coroutine.
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;
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; CHECK-LABEL: define void @simplify_destroy(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call void @print(i32 1)
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; CHECK-NEXT: ret void
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;
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define void @simplify_destroy() {
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entry:
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%id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
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%need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
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br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
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dyn.alloc:
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%size = call i32 @llvm.coro.size.i32()
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%alloc = call i8* @malloc(i32 %size)
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br label %coro.begin
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coro.begin:
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%phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
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%hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
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br label %body
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body:
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%save = call token @llvm.coro.save(i8* %hdl)
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call void @llvm.coro.destroy(i8* %hdl)
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%0 = call i8 @llvm.coro.suspend(token %save, i1 false)
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switch i8 %0, label %suspend [i8 0, label %resume
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i8 1, label %pre.cleanup]
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resume:
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call void @print(i32 0)
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br label %cleanup
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pre.cleanup:
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call void @print(i32 1)
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br label %cleanup
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cleanup:
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%mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
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call void @free(i8* %mem)
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br label %suspend
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suspend:
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call void @llvm.coro.end(i8* %hdl, i1 false)
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ret void
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}
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; SimplifySuspendPoint won't be able to simplify if it detects that there are
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; other calls between coro.save and coro.suspend. They potentially can call
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; resume or destroy, so we should not simplify this suspend point.
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;
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; CHECK-LABEL: define void @cannot_simplify(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: call i8* @malloc
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define void @cannot_simplify() {
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entry:
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%id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
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%need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
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br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
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dyn.alloc:
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%size = call i32 @llvm.coro.size.i32()
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%alloc = call i8* @malloc(i32 %size)
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br label %coro.begin
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coro.begin:
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%phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
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%hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
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br label %body
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body:
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%save = call token @llvm.coro.save(i8* %hdl)
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call void @foo()
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call void @llvm.coro.destroy(i8* %hdl)
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%0 = call i8 @llvm.coro.suspend(token %save, i1 false)
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switch i8 %0, label %suspend [i8 0, label %resume
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i8 1, label %pre.cleanup]
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resume:
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call void @print(i32 0)
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br label %cleanup
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pre.cleanup:
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call void @print(i32 1)
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br label %cleanup
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cleanup:
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%mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
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call void @free(i8* %mem)
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br label %suspend
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suspend:
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call void @llvm.coro.end(i8* %hdl, i1 false)
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ret void
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}
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declare i8* @malloc(i32)
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declare void @free(i8*)
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declare void @print(i32)
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declare void @foo()
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declare token @llvm.coro.id(i32, i8*, i8*, i8*)
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declare i1 @llvm.coro.alloc(token)
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declare i32 @llvm.coro.size.i32()
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declare i8* @llvm.coro.begin(token, i8*)
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declare token @llvm.coro.save(i8* %hdl)
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declare i8 @llvm.coro.suspend(token, i1)
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declare i8* @llvm.coro.free(token, i8*)
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declare void @llvm.coro.end(i8*, i1)
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declare void @llvm.coro.resume(i8*)
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declare void @llvm.coro.destroy(i8*)
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