r335422 - [Coroutines] Less IR for noexcept await_resume
Brian Gesiak via cfe-commits
cfe-commits at lists.llvm.org
Sat Jun 23 11:57:26 PDT 2018
Author: modocache
Date: Sat Jun 23 11:57:26 2018
New Revision: 335422
URL: http://llvm.org/viewvc/llvm-project?rev=335422&view=rev
Log:
[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
Modified:
cfe/trunk/lib/CodeGen/CGCoroutine.cpp
cfe/trunk/test/CodeGenCoroutines/coro-await-resume-eh.cpp
Modified: cfe/trunk/lib/CodeGen/CGCoroutine.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGCoroutine.cpp?rev=335422&r1=335421&r2=335422&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGCoroutine.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGCoroutine.cpp Sat Jun 23 11:57:26 2018
@@ -130,6 +130,16 @@ static SmallString<32> buildSuspendPrefi
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 @@ static LValueOrRValue emitSuspendExpress
// 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 @@ void CodeGenFunction::EmitCoroutineBody(
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 @@ void CodeGenFunction::EmitCoroutineBody(
emitBodyAndFallthrough(*this, S, TryStmt->getTryBlock());
ExitCXXTryStmt(*TryStmt);
- EmitBlock(ContBB);
+ if (ContBB)
+ EmitBlock(ContBB);
}
else {
emitBodyAndFallthrough(*this, S, S.getBody());
Modified: cfe/trunk/test/CodeGenCoroutines/coro-await-resume-eh.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCoroutines/coro-await-resume-eh.cpp?rev=335422&r1=335421&r2=335422&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCoroutines/coro-await-resume-eh.cpp (original)
+++ cfe/trunk/test/CodeGenCoroutines/coro-await-resume-eh.cpp Sat Jun 23 11:57:26 2018
@@ -18,9 +18,9 @@ struct throwing_awaitable {
void await_resume() { throw 42; }
};
-struct task {
+struct throwing_task {
struct promise_type {
- task get_return_object() { return task{}; }
+ auto get_return_object() { return throwing_task{}; }
auto initial_suspend() { return throwing_awaitable{}; }
auto final_suspend() { return coro::suspend_never{}; }
void return_void() {}
@@ -29,7 +29,7 @@ struct task {
};
// CHECK-LABEL: define void @_Z1fv()
-task f() {
+throwing_task f() {
// A variable RESUMETHREW is used to keep track of whether the body
// of 'await_resume' threw an exception. Exceptions thrown in
// 'await_resume' are unwound to RESUMELPAD.
@@ -50,7 +50,7 @@ task f() {
// CHECK: [[RESUMELPAD]]:
// CHECK: br label %[[RESUMECATCH:.+]]
// CHECK: [[RESUMECATCH]]:
- // CHECK: invoke void @_ZN4task12promise_type19unhandled_exceptionEv
+ // CHECK: invoke void @_ZN13throwing_task12promise_type19unhandled_exceptionEv
// CHECK-NEXT: to label %[[RESUMEENDCATCH:.+]] unwind label
// CHECK: [[RESUMEENDCATCH]]:
// CHECK-NEXT: invoke void @__cxa_end_catch()
@@ -67,7 +67,7 @@ task f() {
// CHECK-NEXT: br i1 %[[RESUMETHREWLOAD]], label %[[RESUMEDCONT:.+]], label %[[RESUMEDBODY:.+]]
// CHECK: [[RESUMEDBODY]]:
- // CHECK: invoke void @_ZN4task12promise_type11return_voidEv
+ // CHECK: invoke void @_ZN13throwing_task12promise_type11return_voidEv
// CHECK-NEXT: to label %[[REDUMEDBODYCONT:.+]] unwind label
// CHECK: [[REDUMEDBODYCONT]]:
// CHECK-NEXT: br label %[[COROFINAL:.+]]
@@ -76,6 +76,33 @@ task f() {
// CHECK-NEXT: br label %[[COROFINAL]]
// CHECK: [[COROFINAL]]:
- // CHECK-NEXT: invoke void @_ZN4task12promise_type13final_suspendEv
+ // CHECK-NEXT: invoke void @_ZN13throwing_task12promise_type13final_suspendEv
+ co_return;
+}
+
+struct noexcept_awaitable {
+ bool await_ready() { return true; }
+ void await_suspend(coro::coroutine_handle<>) {}
+ void await_resume() noexcept {}
+};
+
+struct noexcept_task {
+ struct promise_type {
+ auto get_return_object() { return noexcept_task{}; }
+ auto initial_suspend() { return noexcept_awaitable{}; }
+ auto final_suspend() { return coro::suspend_never{}; }
+ void return_void() {}
+ void unhandled_exception() {}
+ };
+};
+
+// CHECK-LABEL: define void @_Z1gv()
+noexcept_task g() {
+ // If the await_resume function is marked as noexcept, none of the additional
+ // conditions that are present in f() above are added to the IR.
+ // This means that no i1 are stored before or after calling await_resume:
+ // CHECK: init.ready:
+ // CHECK-NEXT: call void @_ZN18noexcept_awaitable12await_resumeEv
+ // CHECK-NOT: store i1 false, i1*
co_return;
}
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