r187611 - DebugInfo: Don't prefer declarations over definitions in -flimit-debug-info in C

[David Blaikie]

On Thu, Aug 1, 2013 at 1:57 PM, David Blaikie <dblaikie at gmail.com> wrote:
> Author: dblaikie
> Date: Thu Aug  1 15:57:40 2013
> New Revision: 187611
>
> URL: http://llvm.org/viewvc/llvm-project?rev=187611&view=rev
> Log:
> DebugInfo: Don't prefer declarations over definitions in -flimit-debug-info in C

& with this we only have one extra failure in the GDB 7.5 test suite
with -flimit-debug-info enabled compared to disabled (
http://llvm.org/viewvc/llvm-project/clang-tests-external/trunk/gdb/7.5/gdb/testsuite/gdb.cp/pr10728.exp?view=markup
- which deliberately compiles the TU that uses the type definition
without debug info and the one that uses only pointers with debug
info, so it's exactly what we'd expect from -flimit-debug-info (with
the usual debates about whether that's the Right Thing to do)).
Granted, that's partly because most tests in the suite are C by
default unless something C++-y is required, but there's still a fair
few C++ tests in there that are exercising the -flimit-debug-info
decl-over-def functionality.

>
> Without an ODR, the -flimit-debug-info debug info size optimization of
> emitting declarations for fully defined types when only a declaration is
> needed by the TU, is incorrect. Emit the full definition whenever it's
> available in non-C++.
>
> Added:
>     cfe/trunk/test/CodeGen/debug-info-limited.c
> Modified:
>     cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
>     cfe/trunk/test/CodeGenCXX/debug-info-limited.cpp
>
> Modified: cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDebugInfo.cpp?rev=187611&r1=187610&r2=187611&view=diff
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGDebugInfo.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGDebugInfo.cpp Thu Aug  1 15:57:40 2013
> @@ -1422,7 +1422,7 @@ llvm::DIType CGDebugInfo::CreateType(con
>    // Limited debug info should only remove struct definitions that can
>    // safely be replaced by a forward declaration in the source code.
>    if (DebugKind <= CodeGenOptions::LimitedDebugInfo && Declaration &&
> -      !RD->isCompleteDefinitionRequired()) {
> +      !RD->isCompleteDefinitionRequired() && CGM.getLangOpts().CPlusPlus) {
>      // FIXME: This implementation is problematic; there are some test
>      // cases where we violate the above principle, such as
>      // test/CodeGen/debug-info-records.c .
> @@ -1951,7 +1951,8 @@ llvm::DIType CGDebugInfo::getCompletedTy
>  void CGDebugInfo::completeFwdDecl(const RecordDecl &RD) {
>    // In limited debug info we only want to do this if the complete type was
>    // required.
> -  if (DebugKind <= CodeGenOptions::LimitedDebugInfo)
> +  if (DebugKind <= CodeGenOptions::LimitedDebugInfo &&
> +      CGM.getLangOpts().CPlusPlus)
>      return;
>
>    QualType QTy = CGM.getContext().getRecordType(&RD);
>
> Added: cfe/trunk/test/CodeGen/debug-info-limited.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/debug-info-limited.c?rev=187611&view=auto
> ==============================================================================
> --- cfe/trunk/test/CodeGen/debug-info-limited.c (added)
> +++ cfe/trunk/test/CodeGen/debug-info-limited.c Thu Aug  1 15:57:40 2013
> @@ -0,0 +1,11 @@
> +// RUN: %clang -flimit-debug-info -emit-llvm -g -S %s -o - | FileCheck %s
> +
> +// Ensure we emit the full definition of 'foo' even though only its declaration
> +// is needed, since C has no ODR to ensure that the definition will be the same
> +// in whatever TU actually uses/requires the definition of 'foo'.
> +// CHECK: ; [ DW_TAG_structure_type ] [foo] {{.*}} [def]
> +
> +struct foo {
> +};
> +
> +struct foo *f;
>
> Modified: cfe/trunk/test/CodeGenCXX/debug-info-limited.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/debug-info-limited.cpp?rev=187611&r1=187610&r2=187611&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGenCXX/debug-info-limited.cpp (original)
> +++ cfe/trunk/test/CodeGenCXX/debug-info-limited.cpp Thu Aug  1 15:57:40 2013
> @@ -1,7 +1,6 @@
> -// RUN: %clang  -emit-llvm -g -S %s -o - | FileCheck %s
> +// RUN: %clang -flimit-debug-info -emit-llvm -g -S %s -o - | FileCheck %s
>
> -// TAG_member is used to encode debug info for 'z' in A.
> -// CHECK: TAG_member
> +// CHECK: ; [ DW_TAG_class_type ] [A] {{.*}} [def]
>  class A {
>  public:
>    int z;
> @@ -13,8 +12,7 @@ A *foo (A* x) {
>  }
>
>  // Verify that we're not emitting a full definition of B in limit debug mode.
> -// RUN: %clang -emit-llvm -g -flimit-debug-info -S %s -o - | FileCheck %s
> -// CHECK-NOT: TAG_member
> +// CHECK: ; [ DW_TAG_class_type ] [B] {{.*}} [decl]
>
>  class B {
>  public:
>
>
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