[llvm] r315279 - Ignore all duplicate frame index expression

[Daniel Jasper via llvm-commits]

With this change, we are actually running into the assertion "conflicting
locations for variable". I have re-instantiated the previous detection
logic in r315576.
What would lead to such two variables conflicting?
Reid, can you help generate a test case? I'll forward repro instructions of
internal tests to you.

On Tue, Oct 10, 2017 at 8:46 AM, Bjorn Steinbrink via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: bsteinbr
> Date: Tue Oct 10 00:46:17 2017
> New Revision: 315279
>
> URL: http://llvm.org/viewvc/llvm-project?rev=315279&view=rev
> Log:
> Ignore all duplicate frame index expression
>
> Some passes might duplicate calls to llvm.dbg.declare creating
> duplicate frame index expression which currently trigger an assertion
> which is meant to catch erroneous, overlapping fragment declarations.
> But identical frame index expressions are just redundant and don't
> actually conflict with each other, so we can be more lenient and just
> ignore the duplicates.
>
> Reviewers: aprantl, rnk
>
> Subscribers: llvm-commits, JDevlieghere
>
> Differential Revision: https://reviews.llvm.org/D38540
>
> Modified:
>     llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>     llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/
> AsmPrinter/DwarfDebug.cpp?rev=315279&r1=315278&r2=315279&view=diff
> ============================================================
> ==================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Tue Oct 10 00:46:17
> 2017
> @@ -220,9 +220,34 @@ ArrayRef<DbgVariable::FrameIndexExpr> Db
>                return A.Expr->getFragmentInfo()->OffsetInBits <
>                       B.Expr->getFragmentInfo()->OffsetInBits;
>              });
> +
>    return FrameIndexExprs;
>  }
>
> +void DbgVariable::addMMIEntry(const DbgVariable &V) {
> +  assert(DebugLocListIndex == ~0U && !MInsn && "not an MMI entry");
> +  assert(V.DebugLocListIndex == ~0U && !V.MInsn && "not an MMI entry");
> +  assert(V.Var == Var && "conflicting variable");
> +  assert(V.IA == IA && "conflicting inlined-at location");
> +
> +  assert(!FrameIndexExprs.empty() && "Expected an MMI entry");
> +  assert(!V.FrameIndexExprs.empty() && "Expected an MMI entry");
> +
> +  for (const auto &FIE : V.FrameIndexExprs)
> +    // Ignore duplicate entries.
> +    if (llvm::none_of(FrameIndexExprs, [&](const FrameIndexExpr &Other) {
> +          return FIE.FI == Other.FI && FIE.Expr == Other.Expr;
> +        }))
> +      FrameIndexExprs.push_back(FIE);
> +
> +  assert((FrameIndexExprs.size() == 1 ||
> +          llvm::all_of(FrameIndexExprs,
> +                       [](FrameIndexExpr &FIE) {
> +                         return FIE.Expr && FIE.Expr->isFragment();
> +                       })) &&
> +         "conflicting locations for variable");
> +}
> +
>  static const DwarfAccelTable::Atom TypeAtoms[] = {
>      DwarfAccelTable::Atom(dwarf::DW_ATOM_die_offset,
> dwarf::DW_FORM_data4),
>      DwarfAccelTable::Atom(dwarf::DW_ATOM_die_tag, dwarf::DW_FORM_data2),
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/
> AsmPrinter/DwarfDebug.h?rev=315279&r1=315278&r2=315279&view=diff
> ============================================================
> ==================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h Tue Oct 10 00:46:17
> 2017
> @@ -138,30 +138,7 @@ public:
>    /// Get the FI entries, sorted by fragment offset.
>    ArrayRef<FrameIndexExpr> getFrameIndexExprs() const;
>    bool hasFrameIndexExprs() const { return !FrameIndexExprs.empty(); }
> -
> -  void addMMIEntry(const DbgVariable &V) {
> -    assert(DebugLocListIndex == ~0U && !MInsn && "not an MMI entry");
> -    assert(V.DebugLocListIndex == ~0U && !V.MInsn && "not an MMI entry");
> -    assert(V.Var == Var && "conflicting variable");
> -    assert(V.IA == IA && "conflicting inlined-at location");
> -
> -    assert(!FrameIndexExprs.empty() && "Expected an MMI entry");
> -    assert(!V.FrameIndexExprs.empty() && "Expected an MMI entry");
> -
> -    if (FrameIndexExprs.size()) {
> -      auto *Expr = FrameIndexExprs.back().Expr;
> -      // Get rid of duplicate non-fragment entries. More than one
> non-fragment
> -      // dbg.declare makes no sense so ignore all but the first.
> -      if (!Expr || !Expr->isFragment())
> -        return;
> -    }
> -    FrameIndexExprs.append(V.FrameIndexExprs.begin(),
> V.FrameIndexExprs.end());
> -    assert(llvm::all_of(FrameIndexExprs,
> -                        [](FrameIndexExpr &FIE) {
> -                          return FIE.Expr && FIE.Expr->isFragment();
> -                        }) &&
> -           "conflicting locations for variable");
> -  }
> +  void addMMIEntry(const DbgVariable &V);
>
>    // Translate tag to proper Dwarf tag.
>    dwarf::Tag getTag() const {
>
>
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