erichkeane created this revision.
erichkeane added reviewers: yaxunl, bader, ABataev, aaron.ballman.
erichkeane requested review of this revision.
Herald added a project: clang.
It doesn't really make sense to emit language specific diagnostics
in a discarded statement, and suppressing these diagnostics results in a
programming pattern that many users will feel is quite useful.
Basically, this makes sure we only emit errors from the 'true' side of a
'constexpr if'.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D102251
Files:
clang/include/clang/AST/Stmt.h
clang/lib/AST/Stmt.cpp
clang/lib/Sema/Sema.cpp
clang/test/SemaCUDA/deferred-diags.cu
Index: clang/test/SemaCUDA/deferred-diags.cu
===================================================================
--- clang/test/SemaCUDA/deferred-diags.cu
+++ clang/test/SemaCUDA/deferred-diags.cu
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fcxx-exceptions -fcuda-is-device -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fcxx-exceptions -fcuda-is-device -fsyntax-only -std=c++17 -verify %s
#include "Inputs/cuda.h"
@@ -8,29 +8,55 @@
// expected-error@-1 2{{cannot use 'throw' in __host__ __device__ function}}
}
+inline __host__ __device__ void hasInvalid2() {
+ throw NULL;
+ // expected-error@-1 2{{cannot use 'throw' in __host__ __device__ function}}
+}
+
+inline __host__ __device__ void hasInvalidDiscarded() {
+ // This is only used in the discarded statements below, so this should not diagnose.
+ throw NULL;
+}
+
static __device__ void use0() {
hasInvalid(); // expected-note {{called by 'use0'}}
hasInvalid(); // expected-note {{called by 'use0'}}
+
+ if constexpr (true) {
+ hasInvalid2(); // expected-note {{called by 'use0'}}
+ } else {
+ hasInvalidDiscarded();
+ }
+
+ if constexpr (false) {
+ hasInvalidDiscarded();
+ } else {
+ hasInvalid2(); // expected-note {{called by 'use0'}}
+ }
+
+ if constexpr (false) {
+ hasInvalidDiscarded();
+ }
}
// To avoid excessive diagnostic messages, deferred diagnostics are only
// emitted the first time a function is called.
static __device__ void use1() {
- use0(); // expected-note 2{{called by 'use1'}}
+ use0(); // expected-note 4{{called by 'use1'}}
use0();
}
static __device__ void use2() {
- use1(); // expected-note 2{{called by 'use2'}}
+ use1(); // expected-note 4{{called by 'use2'}}
use1();
}
static __device__ void use3() {
- use2(); // expected-note 2{{called by 'use3'}}
+ use2(); // expected-note 4{{called by 'use3'}}
use2();
}
__global__ void use4() {
- use3(); // expected-note 2{{called by 'use4'}}
+ use3(); // expected-note 4{{called by 'use4'}}
use3();
}
Index: clang/lib/Sema/Sema.cpp
===================================================================
--- clang/lib/Sema/Sema.cpp
+++ clang/lib/Sema/Sema.cpp
@@ -1666,6 +1666,18 @@
}
}
}
+
+ void VisitIfStmt(IfStmt *If) {
+ // Only evaluate the non-discarded side of a constexpr-if.
+ if (Optional<Stmt *> SubStmt = If->getNondiscardedCase(S.Context)) {
+ // The non-discarded statement could can be a non-existent 'else', so make
+ // sure we don't try to visit it.
+ if (*SubStmt)
+ Inherited::Visit(*SubStmt);
+ } else {
+ Inherited::VisitStmt(If);
+ }
+ }
};
} // namespace
Index: clang/lib/AST/Stmt.cpp
===================================================================
--- clang/lib/AST/Stmt.cpp
+++ clang/lib/AST/Stmt.cpp
@@ -989,12 +989,20 @@
return isa<ObjCAvailabilityCheckExpr>(getCond());
}
-Optional<const Stmt*> IfStmt::getNondiscardedCase(const ASTContext &Ctx) const {
+Optional<Stmt *> IfStmt::getNondiscardedCase(const ASTContext &Ctx) {
if (!isConstexpr() || getCond()->isValueDependent())
return None;
return !getCond()->EvaluateKnownConstInt(Ctx) ? getElse() : getThen();
}
+Optional<const Stmt *>
+IfStmt::getNondiscardedCase(const ASTContext &Ctx) const {
+ if (Optional<Stmt *> Result =
+ const_cast<IfStmt *>(this)->getNondiscardedCase(Ctx))
+ return *Result;
+ return None;
+}
+
ForStmt::ForStmt(const ASTContext &C, Stmt *Init, Expr *Cond, VarDecl *condVar,
Expr *Inc, Stmt *Body, SourceLocation FL, SourceLocation LP,
SourceLocation RP)
Index: clang/include/clang/AST/Stmt.h
===================================================================
--- clang/include/clang/AST/Stmt.h
+++ clang/include/clang/AST/Stmt.h
@@ -2080,6 +2080,7 @@
/// If this is an 'if constexpr', determine which substatement will be taken.
/// Otherwise, or if the condition is value-dependent, returns None.
Optional<const Stmt*> getNondiscardedCase(const ASTContext &Ctx) const;
+ Optional<Stmt *> getNondiscardedCase(const ASTContext &Ctx);
bool isObjCAvailabilityCheck() const;
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