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[Coroutines 1/2] Improve symmetric control transfer feature

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Differential Revision: https://reviews.llvm.org/D76911
This commit is contained in:
Jun Ma 2020-03-27 15:15:28 +08:00
parent 8bfc3e764e
commit 9f7a51855e
2 changed files with 101 additions and 5 deletions
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38
lib/Transforms/Coroutines/CoroSplit.cpp
View File

@ -975,6 +975,37 @@ static bool simplifyTerminatorLeadingToRet(Instruction *InitialInst) {
return false;
}
// Check whether CI obeys the rules of musttail attribute.
static bool shouldBeMustTail(const CallInst &CI, const Function &F) {
if (CI.isInlineAsm())
return false;
// Match prototypes and calling conventions of resume function.
FunctionType *CalleeTy = CI.getFunctionType();
if (!CalleeTy->getReturnType()->isVoidTy() || (CalleeTy->getNumParams() != 1))
return false;
Type *CalleeParmTy = CalleeTy->getParamType(0);
if (!CalleeParmTy->isPointerTy() ||
(CalleeParmTy->getPointerAddressSpace() != 0))
return false;
if (CI.getCallingConv() != F.getCallingConv())
return false;
// CI should not has any ABI-impacting function attributes.
static const Attribute::AttrKind ABIAttrs[] = {
Attribute::StructRet, Attribute::ByVal, Attribute::InAlloca,
Attribute::InReg, Attribute::Returned, Attribute::SwiftSelf,
Attribute::SwiftError, Attribute::Alignment};
AttributeList Attrs = CI.getAttributes();
for (auto AK : ABIAttrs)
if (Attrs.hasParamAttribute(0, AK))
return false;
return true;
}
// Add musttail to any resume instructions that is immediately followed by a
// suspend (i.e. ret). We do this even in -O0 to support guaranteed tail call
// for symmetrical coroutine control transfer (C++ Coroutines TS extension).
@ -987,11 +1018,8 @@ static void addMustTailToCoroResumes(Function &F) {
SmallVector<CallInst *, 4> Resumes;
for (auto &I : instructions(F))
if (auto *Call = dyn_cast<CallInst>(&I))
if (auto *CalledValue = Call->getCalledValue())
// CoroEarly pass replaced coro resumes with indirect calls to an
// address return by CoroSubFnInst intrinsic. See if it is one of those.
if (isa<CoroSubFnInst>(CalledValue->stripPointerCasts()))
Resumes.push_back(Call);
if (shouldBeMustTail(*Call, F))
Resumes.push_back(Call);
// Set musttail on those that are followed by a ret instruction.
for (CallInst *Call : Resumes)

68
test/Transforms/Coroutines/coro-split-musttail2.ll Normal file
View File

@ -0,0 +1,68 @@
; Tests that coro-split will convert coro.resume followed by a suspend to a
; musttail call.
; RUN: opt < %s -coro-split -S | FileCheck %s
; RUN: opt < %s -passes=coro-split -S | FileCheck %s
define void @fakeresume1(i8*) {
entry:
ret void;
}
define void @fakeresume2(i64*) {
entry:
ret void;
}
define void @g() #0 {
entry:
%id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
%alloc = call i8* @malloc(i64 16) #3
%vFrame = call noalias nonnull i8* @llvm.coro.begin(token %id, i8* %alloc)
%save = call token @llvm.coro.save(i8* null)
call fastcc void @fakeresume1(i8* null)
%suspend = call i8 @llvm.coro.suspend(token %save, i1 false)
switch i8 %suspend, label %exit [
i8 0, label %await.ready
i8 1, label %exit
]
await.ready:
%save2 = call token @llvm.coro.save(i8* null)
call fastcc void @fakeresume2(i64* null)
%suspend2 = call i8 @llvm.coro.suspend(token %save2, i1 false)
switch i8 %suspend2, label %exit [
i8 0, label %exit
i8 1, label %exit
]
exit:
call i1 @llvm.coro.end(i8* null, i1 false)
ret void
}
; Verify that in the initial function resume is not marked with musttail.
; CHECK-LABEL: @g(
; CHECK-NOT: musttail call fastcc void @fakeresume1(i8* null)
; Verify that in the resume part resume call is marked with musttail.
; CHECK-LABEL: @g.resume(
; CHECK: musttail call fastcc void @fakeresume2(i64* null)
; CHECK-NEXT: ret void
declare token @llvm.coro.id(i32, i8* readnone, i8* nocapture readonly, i8*) #1
declare i1 @llvm.coro.alloc(token) #2
declare i64 @llvm.coro.size.i64() #3
declare i8* @llvm.coro.begin(token, i8* writeonly) #2
declare token @llvm.coro.save(i8*) #2
declare i8* @llvm.coro.frame() #3
declare i8 @llvm.coro.suspend(token, i1) #2
declare i8* @llvm.coro.free(token, i8* nocapture readonly) #1
declare i1 @llvm.coro.end(i8*, i1) #2
declare i8* @llvm.coro.subfn.addr(i8* nocapture readonly, i8) #1
declare i8* @malloc(i64)
attributes #0 = { "coroutine.presplit"="1" }
attributes #1 = { argmemonly nounwind readonly }
attributes #2 = { nounwind }
attributes #3 = { nounwind readnone }