r359809 - Use primary template parameter names for variable template debug info
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Thu May 2 15:13:41 PDT 2019
On Thu, 2 May 2019 at 10:43, Reid Kleckner via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
>
> Author: rnk
> Date: Thu May 2 10:45:54 2019
> New Revision: 359809
>
> URL: http://llvm.org/viewvc/llvm-project?rev=359809&view=rev
> Log:
> Use primary template parameter names for variable template debug info
>
> Summary:
> Fixes PR41677
>
> Consider:
> template <typename LHS, typename RHS> constexpr bool is_same_v = false;
> template <typename T> constexpr bool is_same_v<T, T> = true;
> template constexpr bool is_same_v<int, int>;
>
> Before this change, when emitting debug info for the
> `is_same_v<int, int>` global variable, clang would crash because it
> would try to use the template parameter list from the partial
> specialization to give parameter names to template arguments. This
> doesn't work in general, since a partial specialization can have fewer
> arguments than the primary template. Therefore, always use the primary
> template. Hypothetically we could try to use the parameter names from
> the partial specialization when possible, but it's not clear this really
> helps debugging in practice.
Hmm, consider:
template<typename T> constexpr bool is_pointer = false;
template<typename T> constexpr bool is_pointer<T*> = true;
If I somehow inspect is_pointer<int*> in a debugger, I think it'd be
surprising to find I had T=int* instead of T=int. (This is likely not
a big deal for a case like this, but there could be a lambda on the
right-hand side of the =, and stepping into that should put the right
set of things in scope.)
> Reviewers: JDevlieghere, aprantl, ormris, dblaikie
>
> Subscribers: cfe-commits
>
> Tags: #clang
>
> Differential Revision: https://reviews.llvm.org/D61408
>
> Added:
> cfe/trunk/test/CodeGenCXX/debug-info-var-template-partial.cpp
> Modified:
> cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
> cfe/trunk/test/CodeGenCXX/debug-info-template-member.cpp
>
> Modified: cfe/trunk/lib/CodeGen/CGDebugInfo.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDebugInfo.cpp?rev=359809&r1=359808&r2=359809&view=diff
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGDebugInfo.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGDebugInfo.cpp Thu May 2 10:45:54 2019
> @@ -1827,32 +1827,24 @@ CGDebugInfo::CollectFunctionTemplatePara
> }
>
> llvm::DINodeArray CGDebugInfo::CollectVarTemplateParams(const VarDecl *VL,
> - llvm::DIFile *Unit) {
> - if (auto *TS = dyn_cast<VarTemplateSpecializationDecl>(VL)) {
> - auto T = TS->getSpecializedTemplateOrPartial();
> - auto TA = TS->getTemplateArgs().asArray();
> - // Collect parameters for a partial specialization
> - if (T.is<VarTemplatePartialSpecializationDecl *>()) {
> - const TemplateParameterList *TList =
> - T.get<VarTemplatePartialSpecializationDecl *>()
> - ->getTemplateParameters();
> - return CollectTemplateParams(TList, TA, Unit);
> - }
> -
> - // Collect parameters for an explicit specialization
> - if (T.is<VarTemplateDecl *>()) {
> - const TemplateParameterList *TList = T.get<VarTemplateDecl *>()
> - ->getTemplateParameters();
> - return CollectTemplateParams(TList, TA, Unit);
> - }
> - }
> - return llvm::DINodeArray();
> + llvm::DIFile *Unit) {
> + // Always get the full list of parameters, not just the ones from the
> + // specialization. A partial specialization may have fewer parameters than
> + // there are arguments.
> + auto *TS = dyn_cast<VarTemplateSpecializationDecl>(VL);
> + if (!TS)
> + return llvm::DINodeArray();
> + VarTemplateDecl *T = TS->getSpecializedTemplate();
> + const TemplateParameterList *TList = T->getTemplateParameters();
> + auto TA = TS->getTemplateArgs().asArray();
> + return CollectTemplateParams(TList, TA, Unit);
> }
>
> llvm::DINodeArray CGDebugInfo::CollectCXXTemplateParams(
> const ClassTemplateSpecializationDecl *TSpecial, llvm::DIFile *Unit) {
> - // Always get the full list of parameters, not just the ones from
> - // the specialization.
> + // Always get the full list of parameters, not just the ones from the
> + // specialization. A partial specialization may have fewer parameters than
> + // there are arguments.
> TemplateParameterList *TPList =
> TSpecial->getSpecializedTemplate()->getTemplateParameters();
> const TemplateArgumentList &TAList = TSpecial->getTemplateArgs();
>
> Modified: cfe/trunk/test/CodeGenCXX/debug-info-template-member.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/debug-info-template-member.cpp?rev=359809&r1=359808&r2=359809&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGenCXX/debug-info-template-member.cpp (original)
> +++ cfe/trunk/test/CodeGenCXX/debug-info-template-member.cpp Thu May 2 10:45:54 2019
> @@ -30,7 +30,7 @@ inline int add3(int x) {
> // CHECK: {{![0-9]+}} = distinct !DIGlobalVariable(
> // CHECK-SAME: name: "var"
> // CHECK-SAME: templateParams: {{![0-9]+}}
> -// CHECK: !DITemplateTypeParameter(name: "P", type: {{![0-9]+}})
> +// CHECK: !DITemplateTypeParameter(name: "T", type: {{![0-9]+}})
> // CHECK: {{![0-9]+}} = distinct !DIGlobalVariable(
> // CHECK-SAME: name: "varray"
> // CHECK-SAME: templateParams: {{![0-9]+}}
>
> Added: cfe/trunk/test/CodeGenCXX/debug-info-var-template-partial.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/debug-info-var-template-partial.cpp?rev=359809&view=auto
> ==============================================================================
> --- cfe/trunk/test/CodeGenCXX/debug-info-var-template-partial.cpp (added)
> +++ cfe/trunk/test/CodeGenCXX/debug-info-var-template-partial.cpp Thu May 2 10:45:54 2019
> @@ -0,0 +1,17 @@
> +// RUN: %clang_cc1 -emit-llvm -triple x86_64-linux-gnu %s -o - -debug-info-kind=limited | FileCheck %s
> +
> +template <typename LHS, typename RHS> constexpr bool is_same_v = false;
> +template <typename T> constexpr bool is_same_v<T, T> = true;
> +
> +template constexpr bool is_same_v<int, int>;
> +static_assert(is_same_v<int, int>, "should get partial spec");
> +
> +// Note that the template arguments for the instantiated variable use the
> +// parameter names from the primary template. The partial specialization might
> +// not have enough parameters.
> +
> +// CHECK: distinct !DIGlobalVariable(name: "is_same_v", linkageName: "_Z9is_same_vIiiE", {{.*}} templateParams: ![[PARAMS:[0-9]+]])
> +// CHECK: ![[PARAMS]] = !{![[LHS:[0-9]+]], ![[RHS:[0-9]+]]}
> +// CHECK: ![[LHS]] = !DITemplateTypeParameter(name: "LHS", type: ![[INT:[0-9]+]])
> +// CHECK: ![[INT]] = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
> +// CHECK: ![[RHS]] = !DITemplateTypeParameter(name: "RHS", type: ![[INT]])
>
>
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