[PATCH] D12134: Improve debug info for implicitly captured vars in lambdas
David Blaikie via cfe-commits
cfe-commits at lists.llvm.org
Tue Aug 25 08:48:07 PDT 2015
On Tue, Aug 25, 2015 at 8:44 AM, Bataev, Alexey <a.bataev at hotmail.com>
wrote:
> Debug info points to the real place where it is captured, while
> diagnostics points to the first use of implicitly captured variable.
Right, but I'm trying to understand the justification for why that's the
right thing to do. Why the debug info user would want a different
experience than the compiler diagnostic consumer would want.
- David
>
>
> Best regards,
> Alexey Bataev
> =============
> Software Engineer
> Intel Compiler Team
>
> 25.08.2015 18:22, David Blaikie пишет:
>
>>
>>
>> On Tue, Aug 25, 2015 at 8:18 AM, Bataev, Alexey <a.bataev at hotmail.com
>> <mailto:a.bataev at hotmail.com>> wrote:
>>
>> I though about this. I think it will be more convenient for user
>> to see the diagnostic on the first use of the variable rather than
>> on '=' or '&' symbol.
>>
>>
>> Why the difference between the diagnostic & the debug info, then?
>>
>>
>> Best regards,
>> Alexey Bataev
>> =============
>> Software Engineer
>> Intel Compiler Team
>>
>> 25.08.2015 18 <tel:25.08.2015%2018>:07, David Blaikie пишет:
>>
>>
>>
>> On Tue, Aug 18, 2015 at 9:05 PM, Alexey Bataev via cfe-commits
>> <cfe-commits at lists.llvm.org
>> <mailto:cfe-commits at lists.llvm.org>
>> <mailto:cfe-commits at lists.llvm.org
>>
>> <mailto:cfe-commits at lists.llvm.org>>> wrote:
>>
>> ABataev created this revision.
>> ABataev added reviewers: echristo, rjmccall, rsmith.
>> ABataev added a subscriber: cfe-commits.
>>
>> When variables are implicitly captured in lambdas, debug info
>> generated for captured variables points to location where
>> they are
>> used first. This patch makes debug info to point to capture
>> default location.
>>
>>
>> Not sure if this is the right tradeoff, or if it is, perhaps
>> we should reconsider how our diagnostics work too?
>>
>> Currently if you, say, capture a variable by value and that
>> variable doesn't have an accessible copy ctor, the diagnostic
>> points to the first use. Should we change that too?
>>
>>
>> http://reviews.llvm.org/D12134
>>
>> Files:
>> lib/Sema/SemaLambda.cpp
>> test/CodeGenCXX/debug-lambda-expressions.cpp
>>
>> Index: lib/Sema/SemaLambda.cpp
>>
>> ===================================================================
>> --- lib/Sema/SemaLambda.cpp
>> +++ lib/Sema/SemaLambda.cpp
>> @@ -1377,10 +1377,10 @@
>> }
>>
>> static ExprResult performLambdaVarCaptureInitialization(
>> - Sema &S, LambdaScopeInfo::Capture &Capture,
>> - FieldDecl *Field,
>> + Sema &S, LambdaScopeInfo::Capture &Capture, FieldDecl
>> *Field,
>> SmallVectorImpl<VarDecl *> &ArrayIndexVars,
>> - SmallVectorImpl<unsigned> &ArrayIndexStarts) {
>> + SmallVectorImpl<unsigned> &ArrayIndexStarts, bool
>> ImplicitCapture,
>> + SourceLocation CaptureDefaultLoc) {
>> assert(Capture.isVariableCapture() && "not a variable
>> capture");
>>
>> auto *Var = Capture.getVariable();
>> @@ -1399,7 +1399,10 @@
>> // An entity captured by a lambda-expression is
>> odr-used (3.2) in
>> // the scope containing the lambda-expression.
>> ExprResult RefResult = S.BuildDeclarationNameExpr(
>> - CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(),
>> Loc), Var);
>> + CXXScopeSpec(),
>> + DeclarationNameInfo(Var->getDeclName(),
>> + ImplicitCapture ?
>> CaptureDefaultLoc : Loc),
>> + Var);
>> if (RefResult.isInvalid())
>> return ExprError();
>> Expr *Ref = RefResult.get();
>> @@ -1561,7 +1564,8 @@
>> Expr *Init = From.getInitExpr();
>> if (!Init) {
>> auto InitResult =
>> performLambdaVarCaptureInitialization(
>> - *this, From, *CurField, ArrayIndexVars,
>> ArrayIndexStarts);
>> + *this, From, *CurField, ArrayIndexVars,
>> ArrayIndexStarts,
>> + CaptureDefault != LCD_None, CaptureDefaultLoc);
>> if (InitResult.isInvalid())
>> return ExprError();
>> Init = InitResult.get();
>> Index: test/CodeGenCXX/debug-lambda-expressions.cpp
>>
>> ===================================================================
>> --- test/CodeGenCXX/debug-lambda-expressions.cpp
>> +++ test/CodeGenCXX/debug-lambda-expressions.cpp
>> @@ -14,6 +14,19 @@
>> struct D { D(); D(const D&); int x; };
>> int d(int x) { D y[10]; return [x,y] { return y[x].x; }(); }
>>
>> +// CHECK-LABEL: foo
>> +int foo(int x) {
>> +// CHECK: [[X:%.+]] = alloca i32,
>> +// CHECK: call void @llvm.dbg.declare(
>> +// CHECK: [[X_REF:%.+]] = getelementptr inbounds %{{.+}},
>> %{{.+}}* %{{.+}}, i32 0, i32 0, !dbg ![[DBG_FOO:[0-9]+]]
>> +// CHECK: [[X_VAL:%.+]] = load i32, i32* [[X]], align 4, !dbg
>> ![[DBG_FOO]]
>> +// CHECK: store i32 [[X_VAL]], i32* [[X_REF]], align 4, !dbg
>> ![[DBG_FOO]]
>> +// CHECK: call i32 @{{.+}}, !dbg ![[DBG_FOO]]
>> + return [=] {
>> + return x;
>> + }();
>> +}
>> +
>> // Randomness for file. -- 6
>> // CHECK: [[FILE:.*]] = !DIFile(filename:
>> "{{.*}}debug-lambda-expressions.cpp",
>>
>> @@ -100,3 +113,5 @@
>> // CHECK-SAME: line: [[VAR_LINE]],
>> // CHECK-SAME: elements:
>> ![[VAR_ARGS:[0-9]+]]
>> // CHECK: ![[VAR_ARGS]] = !{!{{[0-9]+}}}
>> +
>> +// CHECK: [[DBG_FOO:![0-9]+]] = !DILocation(line: 25,
>>
>>
>>
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>>
>>
>>
>
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