<div dir="ltr"><div><span style="font-size:12.8px">The assert below is throwing a -Wsign-compare warning because std::distance returns a signed type.</span></div><span style="font-size:12.8px"><div><span style="font-size:12.8px"><br></span></div>+ const size_t NumFields =</span><br style="font-size:12.8px"><span style="font-size:12.8px">+ std::distance(ClosureClass-></span><wbr style="font-size:12.8px"><span style="font-size:12.8px">field_begin(), ClosureClass->field_end());</span><br style="font-size:12.8px"><span style="font-size:12.8px">+</span><br style="font-size:12.8px"><span style="font-size:12.8px">+ assert(NumFields ==</span><br style="font-size:12.8px"><span style="font-size:12.8px">+ std::distance(E->capture_init_</span><wbr style="font-size:12.8px"><span style="font-size:12.8px">begin(), E->capture_init_end()) &&</span><br style="font-size:12.8px"><span style="font-size:12.8px">+ "The number of lambda capture initializers should equal the number of "</span><br style="font-size:12.8px"><span style="font-size:12.8px">+ "fields within the closure type");</span><br></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature">~Craig</div></div>
<br><div class="gmail_quote">On Wed, Feb 15, 2017 at 8:12 PM, Faisal Vali via cfe-commits <span dir="ltr"><<a href="mailto:cfe-commits@lists.llvm.org" target="_blank">cfe-commits@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: faisalv<br>
Date: Wed Feb 15 22:12:21 2017<br>
New Revision: 295279<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=295279&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project?rev=295279&view=rev</a><br>
Log:<br>
[cxx1z-constexpr-lambda] Implement captures - thus completing implementation of constexpr lambdas.<br>
<br>
Enable evaluation of captures within constexpr lambdas by using a strategy similar to that used in CodeGen:<br>
- when starting evaluation of a lambda's call operator, create a map from VarDecl's to a closure's FieldDecls<br>
- every time a VarDecl (or '*this) that represents a capture is encountered while evaluating the expression via the expression evaluator (specifically the LValueEvaluator) in ExprConstant.cpp - it is replaced by the corresponding FieldDecl LValue (an Lvalue-to-Rvalue conversion on this LValue representation then determines the right rvalue when needed).<br>
<br>
Thanks to Richard Smith and Hubert Tong for their review and feedback!<br>
<br>
<a href="https://reviews.llvm.org/D29748" rel="noreferrer" target="_blank">https://reviews.llvm.org/<wbr>D29748</a><br>
<br>
<br>
Modified:<br>
cfe/trunk/lib/AST/<wbr>ExprConstant.cpp<br>
cfe/trunk/test/SemaCXX/cxx1z-<wbr>constexpr-lambdas.cpp<br>
<br>
Modified: cfe/trunk/lib/AST/<wbr>ExprConstant.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=295279&r1=295278&r2=295279&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/cfe/trunk/lib/AST/<wbr>ExprConstant.cpp?rev=295279&<wbr>r1=295278&r2=295279&view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- cfe/trunk/lib/AST/<wbr>ExprConstant.cpp (original)<br>
+++ cfe/trunk/lib/AST/<wbr>ExprConstant.cpp Wed Feb 15 22:12:21 2017<br>
@@ -425,6 +425,17 @@ namespace {<br>
/// Index - The call index of this call.<br>
unsigned Index;<br>
<br>
+ // FIXME: Adding this to every 'CallStackFrame' may have a nontrivial impact<br>
+ // on the overall stack usage of deeply-recursing constexpr evaluataions.<br>
+ // (We should cache this map rather than recomputing it repeatedly.)<br>
+ // But let's try this and see how it goes; we can look into caching the map<br>
+ // as a later change.<br>
+<br>
+ /// LambdaCaptureFields - Mapping from captured variables/this to<br>
+ /// corresponding data members in the closure class.<br>
+ llvm::DenseMap<const VarDecl *, FieldDecl *> LambdaCaptureFields;<br>
+ FieldDecl *LambdaThisCaptureField;<br>
+<br>
CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,<br>
const FunctionDecl *Callee, const LValue *This,<br>
APValue *Arguments);<br>
@@ -2279,6 +2290,10 @@ static bool HandleLValueComplexElement(E<br>
return true;<br>
}<br>
<br>
+static bool handleLValueToRValueConversion<wbr>(EvalInfo &Info, const Expr *Conv,<br>
+ QualType Type, const LValue &LVal,<br>
+ APValue &RVal);<br>
+<br>
/// Try to evaluate the initializer for a variable declaration.<br>
///<br>
/// \param Info Information about the ongoing evaluation.<br>
@@ -2290,6 +2305,7 @@ static bool HandleLValueComplexElement(E<br>
static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,<br>
const VarDecl *VD, CallStackFrame *Frame,<br>
APValue *&Result) {<br>
+<br>
// If this is a parameter to an active constexpr function call, perform<br>
// argument substitution.<br>
if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD)) {<br>
@@ -4180,6 +4196,10 @@ static bool HandleFunctionCall(SourceLoc<br>
return false;<br>
This->moveInto(Result);<br>
return true;<br>
+ } else if (MD && isLambdaCallOperator(MD)) {<br>
+ // We're in a lambda; determine the lambda capture field maps.<br>
+ MD->getParent()-><wbr>getCaptureFields(Frame.<wbr>LambdaCaptureFields,<br>
+ Frame.LambdaThisCaptureField);<br>
}<br>
<br>
StmtResult Ret = {Result, ResultSlot};<br>
@@ -5041,6 +5061,33 @@ bool LValueExprEvaluator::<wbr>VisitDeclRefEx<br>
<br>
<br>
bool LValueExprEvaluator::<wbr>VisitVarDecl(const Expr *E, const VarDecl *VD) {<br>
+<br>
+ // If we are within a lambda's call operator, check whether the 'VD' referred<br>
+ // to within 'E' actually represents a lambda-capture that maps to a<br>
+ // data-member/field within the closure object, and if so, evaluate to the<br>
+ // field or what the field refers to.<br>
+ if (Info.CurrentCall && isLambdaCallOperator(Info.<wbr>CurrentCall->Callee)) {<br>
+ if (auto *FD = Info.CurrentCall-><wbr>LambdaCaptureFields.lookup(VD)<wbr>) {<br>
+ if (Info.<wbr>checkingPotentialConstantExpre<wbr>ssion())<br>
+ return false;<br>
+ // Start with 'Result' referring to the complete closure object...<br>
+ Result = *Info.CurrentCall->This;<br>
+ // ... then update it to refer to the field of the closure object<br>
+ // that represents the capture.<br>
+ if (!HandleLValueMember(Info, E, Result, FD))<br>
+ return false;<br>
+ // And if the field is of reference type, update 'Result' to refer to what<br>
+ // the field refers to.<br>
+ if (FD->getType()-><wbr>isReferenceType()) {<br>
+ APValue RVal;<br>
+ if (!<wbr>handleLValueToRValueConversion<wbr>(Info, E, FD->getType(), Result,<br>
+ RVal))<br>
+ return false;<br>
+ Result.setFrom(Info.Ctx, RVal);<br>
+ }<br>
+ return true;<br>
+ }<br>
+ }<br>
CallStackFrame *Frame = nullptr;<br>
if (VD->hasLocalStorage() && Info.CurrentCall->Index > 1) {<br>
// Only if a local variable was declared in the function currently being<br>
@@ -5440,6 +5487,27 @@ public:<br>
return false;<br>
}<br>
Result = *Info.CurrentCall->This;<br>
+ // If we are inside a lambda's call operator, the 'this' expression refers<br>
+ // to the enclosing '*this' object (either by value or reference) which is<br>
+ // either copied into the closure object's field that represents the '*this'<br>
+ // or refers to '*this'.<br>
+ if (isLambdaCallOperator(Info.<wbr>CurrentCall->Callee)) {<br>
+ // Update 'Result' to refer to the data member/field of the closure object<br>
+ // that represents the '*this' capture.<br>
+ if (!HandleLValueMember(Info, E, Result,<br>
+ Info.CurrentCall-><wbr>LambdaThisCaptureField))<br>
+ return false;<br>
+ // If we captured '*this' by reference, replace the field with its referent.<br>
+ if (Info.CurrentCall-><wbr>LambdaThisCaptureField-><wbr>getType()<br>
+ ->isPointerType()) {<br>
+ APValue RVal;<br>
+ if (!<wbr>handleLValueToRValueConversion<wbr>(Info, E, E->getType(), Result,<br>
+ RVal))<br>
+ return false;<br>
+<br>
+ Result.setFrom(Info.Ctx, RVal);<br>
+ }<br>
+ }<br>
return true;<br>
}<br>
<br>
@@ -6269,14 +6337,40 @@ bool RecordExprEvaluator::<wbr>VisitLambdaExp<br>
if (ClosureClass->isInvalidDecl()<wbr>) return false;<br>
<br>
if (Info.<wbr>checkingPotentialConstantExpre<wbr>ssion()) return true;<br>
- if (E->capture_size()) {<br>
- Info.FFDiag(E, diag::note_unimplemented_<wbr>constexpr_lambda_feature_ast)<br>
- << "can not evaluate lambda expressions with captures";<br>
- return false;<br>
+<br>
+ const size_t NumFields =<br>
+ std::distance(ClosureClass-><wbr>field_begin(), ClosureClass->field_end());<br>
+<br>
+ assert(NumFields ==<br>
+ std::distance(E->capture_init_<wbr>begin(), E->capture_init_end()) &&<br>
+ "The number of lambda capture initializers should equal the number of "<br>
+ "fields within the closure type");<br>
+<br>
+ Result = APValue(APValue::UninitStruct(<wbr>), /*NumBases*/0, NumFields);<br>
+ // Iterate through all the lambda's closure object's fields and initialize<br>
+ // them.<br>
+ auto *CaptureInitIt = E->capture_init_begin();<br>
+ const LambdaCapture *CaptureIt = ClosureClass->captures_begin()<wbr>;<br>
+ bool Success = true;<br>
+ for (const auto *Field : ClosureClass->fields()) {<br>
+ assert(CaptureInitIt != E->capture_init_end());<br>
+ // Get the initializer for this field<br>
+ Expr *const CurFieldInit = *CaptureInitIt++;<br>
+<br>
+ // If there is no initializer, either this is a VLA or an error has<br>
+ // occurred.<br>
+ if (!CurFieldInit)<br>
+ return Error(E);<br>
+<br>
+ APValue &FieldVal = Result.getStructField(Field-><wbr>getFieldIndex());<br>
+ if (!EvaluateInPlace(FieldVal, Info, This, CurFieldInit)) {<br>
+ if (!Info.<wbr>keepEvaluatingAfterFailure())<br>
+ return false;<br>
+ Success = false;<br>
+ }<br>
+ ++CaptureIt;<br>
}<br>
- // FIXME: Implement captures.<br>
- Result = APValue(APValue::UninitStruct(<wbr>), /*NumBases*/0, /*NumFields*/0);<br>
- return true;<br>
+ return Success;<br>
}<br>
<br>
static bool EvaluateRecord(const Expr *E, const LValue &This,<br>
<br>
Modified: cfe/trunk/test/SemaCXX/cxx1z-<wbr>constexpr-lambdas.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/cxx1z-constexpr-lambdas.cpp?rev=295279&r1=295278&r2=295279&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/cfe/trunk/test/<wbr>SemaCXX/cxx1z-constexpr-<wbr>lambdas.cpp?rev=295279&r1=<wbr>295278&r2=295279&view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- cfe/trunk/test/SemaCXX/cxx1z-<wbr>constexpr-lambdas.cpp (original)<br>
+++ cfe/trunk/test/SemaCXX/cxx1z-<wbr>constexpr-lambdas.cpp Wed Feb 15 22:12:21 2017<br>
@@ -1,6 +1,6 @@<br>
-// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks %s<br>
-// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing %s<br>
-// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -fblocks %s -DCPP14_AND_EARLIER<br>
+// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks %s -fcxx-exceptions<br>
+// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing %s -fcxx-exceptions<br>
+// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -fblocks %s -DCPP14_AND_EARLIER -fcxx-exceptions<br>
<br>
<br>
namespace test_lambda_is_literal {<br>
@@ -157,18 +157,115 @@ constexpr auto M = // expected-error{{m<br>
<br>
} // end ns1_simple_lambda<br>
<br>
-namespace ns1_unimplemented {<br>
-namespace ns1_captures {<br>
+namespace test_captures_1 {<br>
+namespace ns1 {<br>
constexpr auto f(int i) {<br>
- double d = 3.14;<br>
- auto L = [=](auto a) { //expected-note{{coming soon}}<br>
- int Isz = i + d;<br>
- return sizeof(i) + sizeof(a) + sizeof(d);<br>
+ struct S { int x; } s = { i * 2 };<br>
+ auto L = [=](auto a) {<br>
+ return i + s.x + a;<br>
+ };<br>
+ return L;<br>
+}<br>
+constexpr auto M = f(3);<br>
+<br>
+static_assert(M(10) == 19);<br>
+<br>
+} // end test_captures_1::ns1<br>
+<br>
+namespace ns2 {<br>
+<br>
+constexpr auto foo(int n) {<br>
+ auto L = [i = n] (auto N) mutable {<br>
+ if (!N(i)) throw "error";<br>
+ return [&i] {<br>
+ return ++i;<br>
+ };<br>
};<br>
+ auto M = L([n](int p) { return p == n; });<br>
+ M(); M();<br>
+ L([n](int p) { return p == n + 2; });<br>
+<br>
return L;<br>
}<br>
-constexpr auto M = f(3); //expected-error{{constant expression}} expected-note{{in call to}}<br>
-} // end ns1_captures<br>
+<br>
+constexpr auto L = foo(3);<br>
+<br>
+} // end test_captures_1::ns2<br>
+namespace ns3 {<br>
+<br>
+constexpr auto foo(int n) {<br>
+ auto L = [i = n] (auto N) mutable {<br>
+ if (!N(i)) throw "error";<br>
+ return [&i] {<br>
+ return [i]() mutable {<br>
+ return ++i;<br>
+ };<br>
+ };<br>
+ };<br>
+ auto M = L([n](int p) { return p == n; });<br>
+ M()(); M()();<br>
+ L([n](int p) { return p == n; });<br>
+<br>
+ return L;<br>
+}<br>
+<br>
+constexpr auto L = foo(3);<br>
+} // end test_captures_1::ns3<br>
+<br>
+namespace ns2_capture_this_byval {<br>
+struct S {<br>
+ int s;<br>
+ constexpr S(int s) : s{s} { }<br>
+ constexpr auto f(S o) {<br>
+ return [*this,o] (auto a) { return s + o.s + a.s; };<br>
+ }<br>
+};<br>
+<br>
+constexpr auto L = S{5}.f(S{10});<br>
+static_assert(L(S{100}) == 115);<br>
+} // end test_captures_1::ns2_capture_<wbr>this_byval<br>
+<br>
+namespace ns2_capture_this_byref {<br>
+<br>
+struct S {<br>
+ int s;<br>
+ constexpr S(int s) : s{s} { }<br>
+ constexpr auto f() const {<br>
+ return [this] { return s; };<br>
+ }<br>
+};<br>
+<br>
+constexpr S SObj{5};<br>
+constexpr auto L = SObj.f();<br>
+constexpr int I = L();<br>
+static_assert(I == 5);<br>
+<br>
+} // end ns2_capture_this_byref<br>
+<br>
+} // end test_captures_1<br>
+<br>
+namespace test_capture_array {<br>
+namespace ns1 {<br>
+constexpr auto f(int I) {<br>
+ int arr[] = { I, I *2, I * 3 };<br>
+ auto L1 = [&] (auto a) { return arr[a]; };<br>
+ int r = L1(2);<br>
+ struct X { int x, y; };<br>
+ return [=](auto a) { return X{arr[a],r}; };<br>
+}<br>
+constexpr auto L = f(3);<br>
+static_assert(L(0).x == 3);<br>
+static_assert(L(0).y == 9);<br>
+static_assert(L(1).x == 6);<br>
+static_assert(L(1).y == 9);<br>
+} // end ns1<br>
+<br>
+} // end test_capture_array<br>
+namespace ns1_test_lvalue_type {<br>
+ void f() {<br>
+ volatile int n;<br>
+ constexpr bool B = [&]{ return &n; }() == &n; // should be accepted<br>
+ }<br>
} // end ns1_unimplemented<br>
<br>
} // end ns test_lambda_is_cce<br>
<br>
<br>
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</blockquote></div><br></div>