faisalv created this revision.
faisalv added a project: clang-c.
Herald added a subscriber: EricWF.
This patch attempts to enable evaluation of all forms of captures (however
deeply nested) within constexpr lambdas.
Appreciate the feedback.
Thanks!
Repository:
rL LLVM
https://reviews.llvm.org/D29748
Files:
lib/AST/ExprConstant.cpp
test/SemaCXX/cxx1z-constexpr-lambdas.cpp
Index: test/SemaCXX/cxx1z-constexpr-lambdas.cpp
===================================================================
--- test/SemaCXX/cxx1z-constexpr-lambdas.cpp
+++ test/SemaCXX/cxx1z-constexpr-lambdas.cpp
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks %s
-// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing %s
-// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -fblocks %s -DCPP14_AND_EARLIER
+// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks %s -fcxx-exceptions
+// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing %s -fcxx-exceptions
+// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -fblocks %s -DCPP14_AND_EARLIER -fcxx-exceptions
namespace test_lambda_is_literal {
@@ -157,18 +157,111 @@
} // end ns1_simple_lambda
-namespace ns1_unimplemented {
-namespace ns1_captures {
+namespace test_captures_1 {
+namespace ns1 {
constexpr auto f(int i) {
- double d = 3.14;
- auto L = [=](auto a) { //expected-note{{coming soon}}
- int Isz = i + d;
- return sizeof(i) + sizeof(a) + sizeof(d);
+ struct S { int x; } s = { i * 2 };
+ auto L = [=](auto a) {
+ return i + s.x + a;
};
return L;
}
-constexpr auto M = f(3); //expected-error{{constant expression}} expected-note{{in call to}}
-} // end ns1_captures
+constexpr auto M = f(3);
+
+static_assert(M(10) == 19);
+
+} // end test_captures_1::ns1
+
+namespace ns2 {
+
+constexpr auto foo(int n) {
+ auto L = [i = n] (auto N) mutable {
+ if (!N(i)) throw "error";
+ return [&i] {
+ return ++i;
+ };
+ };
+ auto M = L([n](int p) { return p == n; });
+ M(); M();
+ L([n](int p) { return p == n + 2; });
+
+ return L;
+}
+
+constexpr auto L = foo(3);
+
+} // end test_captures_1::ns2
+namespace ns3 {
+
+constexpr auto foo(int n) {
+ auto L = [i = n] (auto N) mutable {
+ if (!N(i)) throw "error";
+ return [&i] {
+ return [i]() mutable {
+ return ++i;
+ };
+ };
+ };
+ auto M = L([n](int p) { return p == n; });
+ M()(); M()();
+ L([n](int p) { return p == n; });
+
+ return L;
+}
+
+constexpr auto L = foo(3);
+} // end test_captures_1::ns3
+
+namespace ns2_capture_this_byval {
+struct S {
+ int s;
+ constexpr S(int s) : s{s} { }
+ constexpr auto f(S o) {
+ return [*this,o] (auto a) { return s + o.s + a.s; };
+ }
+};
+
+constexpr auto L = S{5}.f(S{10});
+static_assert(L(S{100}) == 115);
+} // end test_captures_1::ns2_capture_this_byval
+
+namespace ns2_capture_this_byref {
+
+struct S {
+ int s;
+ constexpr S(int s) : s{s} { }
+ constexpr auto f() const {
+ return [this] { return s; };
+ }
+};
+
+constexpr S SObj{5};
+constexpr auto L = SObj.f();
+constexpr int I = L();
+static_assert(I == 5);
+
+} // end ns2_capture_this_byref
+
+} // end test_captures_1
+
+namespace test_capture_array {
+namespace ns1 {
+constexpr auto f(int I) {
+ int arr[] = { I, I *2, I * 3 };
+ auto L1 = [&] (auto a) { return arr[a]; };
+ int r = L1(2);
+ struct X { int x, y; };
+ return [=](auto a) { return X{arr[a],r}; };
+}
+constexpr auto L = f(3);
+static_assert(L(0).x == 3);
+static_assert(L(0).y == 9);
+static_assert(L(1).x == 6);
+static_assert(L(1).y == 9);
+} // end ns1
+
+} // end test_capture_array
+namespace ns1_unimplemented {
} // end ns1_unimplemented
} // end ns test_lambda_is_cce
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -425,6 +425,9 @@
/// Index - The call index of this call.
unsigned Index;
+ llvm::DenseMap<const VarDecl *, FieldDecl *> LambdaCaptureFields;
+ FieldDecl *LambdaThisCaptureField;
+
CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
const FunctionDecl *Callee, const LValue *This,
APValue *Arguments);
@@ -2279,6 +2282,10 @@
return true;
}
+static bool handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv,
+ QualType Type, const LValue &LVal,
+ APValue &RVal);
+
/// Try to evaluate the initializer for a variable declaration.
///
/// \param Info Information about the ongoing evaluation.
@@ -2290,6 +2297,7 @@
static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
const VarDecl *VD, CallStackFrame *Frame,
APValue *&Result) {
+
// If this is a parameter to an active constexpr function call, perform
// argument substitution.
if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD)) {
@@ -4180,6 +4188,10 @@
return false;
This->moveInto(Result);
return true;
+ } else if (MD && isLambdaCallOperator(MD)) {
+ // We're in a lambda; determine the lambda capture field maps.
+ MD->getParent()->getCaptureFields(Frame.LambdaCaptureFields,
+ Frame.LambdaThisCaptureField);
}
StmtResult Ret = {Result, ResultSlot};
@@ -5034,6 +5046,35 @@
bool LValueExprEvaluator::VisitVarDecl(const Expr *E, const VarDecl *VD) {
+
+ if (Info.CurrentCall && isLambdaCallOperator(Info.CurrentCall->Callee)) {
+ if (auto *FD = Info.CurrentCall->LambdaCaptureFields.lookup(VD)) {
+ if (Info.checkingPotentialConstantExpression())
+ return false;
+ Result = *Info.CurrentCall->This;
+ // Set Result to the subobject of the lambda
+ if (HandleLValueMember(Info, E, Result, FD)) {
+ // If the field is of reference type, replace it with the variable or
+ // enclosing field it refers to, otherwise use the value of the field.
+ if (FD->getType()->isReferenceType()) {
+ APValue RVal;
+ // FIXME: We need to make sure we're passing the right type that
+ // maintains cv-qualifiers.
+ if (!handleLValueToRValueConversion(Info, E, E->getType(), Result,
+ RVal))
+ return false;
+ assert(RVal.isLValue() && "Reference captures through their "
+ "corresponding field members must refer to "
+ "lvalues (VarDecls or FieldDecls)");
+ Result.setFrom(Info.Ctx, RVal);
+ }
+ return true;
+ }
+
+ Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
+ return false;
+ }
+ }
CallStackFrame *Frame = nullptr;
if (VD->hasLocalStorage() && Info.CurrentCall->Index > 1) {
// Only if a local variable was declared in the function currently being
@@ -5423,6 +5464,28 @@
return false;
}
Result = *Info.CurrentCall->This;
+ // If we are inside a lambda's call operator, the 'this' expression refers
+ // to the enclosing '*this' object (either by value or reference) which is
+ // either copied into the closure object's field that represents the '*this'
+ // or refers to '*this'.
+ if (isLambdaCallOperator(Info.CurrentCall->Callee)) {
+
+ if (HandleLValueMember(Info, E, Result,
+ Info.CurrentCall->LambdaThisCaptureField)) {
+ if (Info.CurrentCall->LambdaThisCaptureField->getType()
+ ->isPointerType()) {
+ APValue RVal;
+ if (!handleLValueToRValueConversion(Info, E, E->getType(), Result,
+ RVal))
+ return false;
+
+ Result.setFrom(Info.Ctx, RVal);
+ }
+ return true;
+ }
+ //Info.FFDiag(E);
+ return false;
+ }
return true;
}
@@ -6250,14 +6313,40 @@
if (ClosureClass->isInvalidDecl()) return false;
if (Info.checkingPotentialConstantExpression()) return true;
- if (E->capture_size()) {
- Info.FFDiag(E, diag::note_unimplemented_constexpr_lambda_feature_ast)
- << "can not evaluate lambda expressions with captures";
- return false;
+
+ const size_t NumFields =
+ std::distance(ClosureClass->field_begin(), ClosureClass->field_end());
+
+ assert(NumFields ==
+ std::distance(E->capture_init_begin(), E->capture_init_end()) &&
+ "The number of lambda capture initializers should equal the number of "
+ "fields within the closure type");
+
+ Result = APValue(APValue::UninitStruct(), /*NumBases*/0, NumFields);
+ // Iterate through all the lambda's closure object's fields and initialize
+ // them.
+ auto *CaptureInitIt = E->capture_init_begin();
+ const LambdaCapture *CaptureIt = ClosureClass->captures_begin();
+ bool Success = true;
+ for (const auto *Field : ClosureClass->fields()) {
+ assert(CaptureInitIt != E->capture_init_end());
+ // Get the initializer for this field
+ Expr *const CurFieldInit = *CaptureInitIt++;
+
+ // If there is no initializer, either this is a VLA or an error has
+ // occurred.
+ if (!CurFieldInit)
+ return false;
+
+ APValue &FieldVal = Result.getStructField(Field->getFieldIndex());
+ if (!EvaluateInPlace(FieldVal, Info, This, CurFieldInit)) {
+ if (!Info.keepEvaluatingAfterFailure())
+ return false;
+ Success = false;
+ }
+ ++CaptureIt;
}
- // FIXME: Implement captures.
- Result = APValue(APValue::UninitStruct(), /*NumBases*/0, /*NumFields*/0);
- return true;
+ return Success;
}
static bool EvaluateRecord(const Expr *E, const LValue &This,
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