https://github.com/yuxuanchen1997 created
https://github.com/llvm/llvm-project/pull/108474
None
>From a4736c1effa479692157dbe735fa873b233f98bd Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <y...@meta.com>
Date: Thu, 12 Sep 2024 17:13:57 -0700
Subject: [PATCH] [Clang] Propagate elide safe context through
[[clang::coro_must_await]]
---
clang/include/clang/Basic/Attr.td | 8 ++++
clang/include/clang/Basic/AttrDocs.td | 12 +++++
clang/lib/Sema/SemaCoroutine.cpp | 48 ++++++++++++++-----
.../CodeGenCoroutines/coro-await-elidable.cpp | 19 ++++++++
4 files changed, 76 insertions(+), 11 deletions(-)
diff --git a/clang/include/clang/Basic/Attr.td
b/clang/include/clang/Basic/Attr.td
index 9a7b163b2c6da8..cd29f08a3320e7 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -1258,6 +1258,14 @@ def CoroAwaitElidable : InheritableAttr {
let SimpleHandler = 1;
}
+def CoroMustAwait : InheritableAttr {
+ let Spellings = [Clang<"coro_must_await">];
+ let Subjects = SubjectList<[ParmVar]>;
+ let LangOpts = [CPlusPlus];
+ let Documentation = [CoroMustAwaitDoc];
+ let SimpleHandler = 1;
+}
+
// OSObject-based attributes.
def OSConsumed : InheritableParamAttr {
let Spellings = [Clang<"os_consumed">];
diff --git a/clang/include/clang/Basic/AttrDocs.td
b/clang/include/clang/Basic/AttrDocs.td
index 9f72456d2da678..2403cb4d2f994a 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -8301,6 +8301,18 @@ callee coroutine.
}];
}
+def CoroMustAwaitDoc : Documentation {
+ let Category = DocCatDecl;
+ let Content = [{
+A direct call expression which returned a prvalue of a type attributed
+[[clang::coro_await_elidable]] is said to be under a SafeElide context
+if one of the following is true:
+- it is the right-hand side operand to an co_await expression.
+- it is an argument to a [[clang::coro_must_await]] parameter or
+parameter pack of another direct call expression under a SafeElide context.
+}];
+}
+
def CountedByDocs : Documentation {
let Category = DocCatField;
let Content = [{
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index a574d56646f3a2..17ffd24a3eb3e4 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -849,12 +849,40 @@ static bool isAttributedCoroAwaitElidable(const QualType
&QT) {
return Record && Record->hasAttr<CoroAwaitElidableAttr>();
}
-static bool isCoroAwaitElidableCall(Expr *Operand) {
+static void applyAwaitElidableContext(Expr *Operand) {
if (!Operand->isPRValue()) {
- return false;
+ return;
}
- return isAttributedCoroAwaitElidable(Operand->getType());
+ auto *Call = dyn_cast<CallExpr>(Operand->IgnoreImplicit());
+ if (!Call)
+ return;
+
+ if (!isAttributedCoroAwaitElidable(Call->getType()))
+ return;
+
+ Call->setCoroElideSafe();
+
+ // Check parameter
+ auto *Fn = llvm::dyn_cast_if_present<FunctionDecl>(Call->getCalleeDecl());
+ if (!Fn)
+ return;
+
+ size_t ParmIdx = 0;
+ for (ParmVarDecl *PD : Fn->parameters()) {
+ if (PD->hasAttr<CoroMustAwaitAttr>()) {
+ if (PD->isParameterPack()) {
+ size_t NumArgs = Call->getNumArgs();
+ for (size_t ArgIdx = ParmIdx; ArgIdx < NumArgs; ArgIdx++) {
+ applyAwaitElidableContext(Call->getArg(ArgIdx));
+ }
+ break;
+ } else {
+ applyAwaitElidableContext(Call->getArg(ParmIdx));
+ }
+ }
+ ParmIdx++;
+ }
}
// Attempts to resolve and build a CoawaitExpr from "raw" inputs, bailing out
to
@@ -880,14 +908,12 @@ ExprResult
Sema::BuildUnresolvedCoawaitExpr(SourceLocation Loc, Expr *Operand,
}
auto *RD = Promise->getType()->getAsCXXRecordDecl();
- bool AwaitElidable =
- isCoroAwaitElidableCall(Operand) &&
- isAttributedCoroAwaitElidable(
- getCurFunctionDecl(/*AllowLambda=*/true)->getReturnType());
-
- if (AwaitElidable)
- if (auto *Call = dyn_cast<CallExpr>(Operand->IgnoreImplicit()))
- Call->setCoroElideSafe();
+
+ bool CurFnAwaitElidable = isAttributedCoroAwaitElidable(
+ getCurFunctionDecl(/*AllowLambda=*/true)->getReturnType());
+
+ if (CurFnAwaitElidable)
+ applyAwaitElidableContext(Operand);
Expr *Transformed = Operand;
if (lookupMember(*this, "await_transform", RD, Loc)) {
diff --git a/clang/test/CodeGenCoroutines/coro-await-elidable.cpp
b/clang/test/CodeGenCoroutines/coro-await-elidable.cpp
index 8512995dfad45a..9e28f0351875cb 100644
--- a/clang/test/CodeGenCoroutines/coro-await-elidable.cpp
+++ b/clang/test/CodeGenCoroutines/coro-await-elidable.cpp
@@ -84,4 +84,23 @@ Task<int> nonelidable() {
co_return 1;
}
+// CHECK-LABEL: define{{.*}} @_Z8addTasks4TaskIiES0_{{.*}} {
+Task<int> addTasks([[clang::coro_must_await]] Task<int> t1, Task<int> t2) {
+ int i1 = co_await t1;
+ int i2 = co_await t2;
+ co_return i1 + i2;
+}
+
+// CHECK-LABEL: define{{.*}} @_Z10returnSamei{{.*}} {
+Task<int> returnSame(int i) {
+ co_return i;
+}
+
+// CHECK-LABEL: define{{.*}} @_Z21elidableWithMustAwaitv{{.*}} {
+Task<int> elidableWithMustAwait() {
+ // CHECK: call void @_Z10returnSamei(ptr {{.*}}, i32 noundef 2)
#[[ELIDE_SAFE]]
+ // CHECK-NOT: call void @_Z10returnSamei(ptr {{.*}}, i32 noundef 3)
#[[ELIDE_SAFE]]
+ co_return co_await addTasks(returnSame(2), returnSame(3));
+}
+
// CHECK: attributes #[[ELIDE_SAFE]] = { coro_elide_safe }
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