[PATCH] D12134: Improve debug info for implicitly captured vars in lambdas
Eric Christopher via cfe-commits
cfe-commits at lists.llvm.org
Tue Aug 25 09:00:06 PDT 2015
Yeah. I can't see a difference here being useful, and more likely harmful.
On Tue, Aug 25, 2015, 8:48 AM David Blaikie <dblaikie at gmail.com> wrote:
> 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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