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

[Bataev, Alexey via cfe-commits]

Debug info points to the real place where it is captured, while 
diagnostics points to the first use of implicitly captured variable.

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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