[Coroutines] Less IR for noexcept await_resume
Summary:
In his review of https://reviews.llvm.org/D45860, @GorNishanov suggested
avoiding generating additional exception-handling IR in the case that
the resume function was marked as 'noexcept', and exceptions could not
occur. This implements that suggestion.
Test Plan: `check-clang`
Reviewers: GorNishanov, EricWF
Reviewed By: GorNishanov
Subscribers: cfe-commits, GorNishanov
Differential Revision: https://reviews.llvm.org/D47673
llvm-svn: 335422
diff --git a/clang/lib/CodeGen/CGCoroutine.cpp b/clang/lib/CodeGen/CGCoroutine.cpp
index bd16896..4f525c8 100644
--- a/clang/lib/CodeGen/CGCoroutine.cpp
+++ b/clang/lib/CodeGen/CGCoroutine.cpp
@@ -130,6 +130,16 @@
return Prefix;
}
+static bool memberCallExpressionCanThrow(const Expr *E) {
+ if (const auto *CE = dyn_cast<CXXMemberCallExpr>(E))
+ if (const auto *Proto =
+ CE->getMethodDecl()->getType()->getAs<FunctionProtoType>())
+ if (isNoexceptExceptionSpec(Proto->getExceptionSpecType()) &&
+ Proto->canThrow() == CT_Cannot)
+ return false;
+ return true;
+}
+
// Emit suspend expression which roughly looks like:
//
// auto && x = CommonExpr();
@@ -217,8 +227,12 @@
// Emit await_resume expression.
CGF.EmitBlock(ReadyBlock);
+
+ // Exception handling requires additional IR. If the 'await_resume' function
+ // is marked as 'noexcept', we avoid generating this additional IR.
CXXTryStmt *TryStmt = nullptr;
- if (Coro.ExceptionHandler && Kind == AwaitKind::Init) {
+ if (Coro.ExceptionHandler && Kind == AwaitKind::Init &&
+ memberCallExpressionCanThrow(S.getResumeExpr())) {
Coro.ResumeEHVar =
CGF.CreateTempAlloca(Builder.getInt1Ty(), Prefix + Twine("resume.eh"));
Builder.CreateFlagStore(true, Coro.ResumeEHVar);
@@ -625,12 +639,20 @@
CurCoro.Data->CurrentAwaitKind = AwaitKind::Normal;
if (CurCoro.Data->ExceptionHandler) {
- BasicBlock *BodyBB = createBasicBlock("coro.resumed.body");
- BasicBlock *ContBB = createBasicBlock("coro.resumed.cont");
- Value *SkipBody =
- Builder.CreateFlagLoad(CurCoro.Data->ResumeEHVar, "coro.resumed.eh");
- Builder.CreateCondBr(SkipBody, ContBB, BodyBB);
- EmitBlock(BodyBB);
+ // If we generated IR to record whether an exception was thrown from
+ // 'await_resume', then use that IR to determine whether the coroutine
+ // body should be skipped.
+ // If we didn't generate the IR (perhaps because 'await_resume' was marked
+ // as 'noexcept'), then we skip this check.
+ BasicBlock *ContBB = nullptr;
+ if (CurCoro.Data->ResumeEHVar) {
+ BasicBlock *BodyBB = createBasicBlock("coro.resumed.body");
+ ContBB = createBasicBlock("coro.resumed.cont");
+ Value *SkipBody = Builder.CreateFlagLoad(CurCoro.Data->ResumeEHVar,
+ "coro.resumed.eh");
+ Builder.CreateCondBr(SkipBody, ContBB, BodyBB);
+ EmitBlock(BodyBB);
+ }
auto Loc = S.getLocStart();
CXXCatchStmt Catch(Loc, /*exDecl=*/nullptr,
@@ -642,7 +664,8 @@
emitBodyAndFallthrough(*this, S, TryStmt->getTryBlock());
ExitCXXTryStmt(*TryStmt);
- EmitBlock(ContBB);
+ if (ContBB)
+ EmitBlock(ContBB);
}
else {
emitBodyAndFallthrough(*this, S, S.getBody());