[PATCH] D12134: Improve debug info for implicitly captured vars in lambdas

[Bataev, Alexey via cfe-commits]

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.

Best regards,
Alexey Bataev
=============
Software Engineer
Intel Compiler Team

25.08.2015 18:07, 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>> 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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