[PATCH] D27980: stripDebugInfo() should remove DILocation's found in !llvm.loop metadata

[Justin Bogner via llvm-commits]

Daniel Sanders via Phabricator via llvm-commits
<llvm-commits at lists.llvm.org> writes:
> dsanders created this revision.
> dsanders added a subscriber: llvm-commits.
>
> Patch by Michele Scandale
> (with a small tweak to 'CHECK-NOT' the last DILocation in the test)
>
>
> https://reviews.llvm.org/D27980
>
> Files:
>   lib/IR/DebugInfo.cpp
>   test/DebugInfo/strip-loop-metadata.ll
>
> Index: test/DebugInfo/strip-loop-metadata.ll
> ===================================================================
> --- /dev/null
> +++ test/DebugInfo/strip-loop-metadata.ll
> @@ -0,0 +1,71 @@
> +; RUN: opt -S -strip-debug < %s | FileCheck %s
> +
> +target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-apple-macosx10.12.0"
> +
> +; CHECK-LABEL: _Z5test1v
> +; CHECK-NOT: br {{.*}} !llvm.loop
> +define void @_Z5test1v() !dbg !7 {
> +entry:
> +  br label %while.body, !dbg !9
> +
> +while.body:
> +  call void @_Z3barv(), !dbg !10
> +  br label %while.body, !dbg !11, !llvm.loop !13
> +
> +return:
> +  ret void, !dbg !14
> +}
> +
> +declare void @_Z3barv()
> +
> +; CHECK-LABEL: _Z5test2v
> +; CHECK: br {{.*}} !llvm.loop [[LOOP:![0-9]+]]
> +define void @_Z5test2v() !dbg !15 {
> +entry:
> +  br label %while.body, !dbg !16
> +
> +while.body:
> +  call void @_Z3barv(), !dbg !17
> +  br label %while.body, !dbg !18, !llvm.loop !19
> +
> +return:
> +  ret void, !dbg !21
> +}
> +
> +!llvm.dbg.cu = !{!0}
> +!llvm.module.flags = !{!3, !4, !5}
> +!llvm.ident = !{!6}
> +
> +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 4.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
> +!1 = !DIFile(filename: "test.cpp", directory: "/tmp")
> +!2 = !{}
> +!3 = !{i32 2, !"Dwarf Version", i32 4}
> +!4 = !{i32 2, !"Debug Info Version", i32 3}
> +!5 = !{i32 1, !"PIC Level", i32 2}
> +!6 = !{!"clang version 4.0.0"}
> +!7 = distinct !DISubprogram(name: "test1", scope: !1, file: !1, line: 3, type: !8, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
> +!8 = !DISubroutineType(types: !2)
> +!9 = !DILocation(line: 4, column: 3, scope: !7)
> +!10 = !DILocation(line: 5, column: 5, scope: !7)
> +!11 = !DILocation(line: 4, column: 3, scope: !12)
> +!12 = !DILexicalBlockFile(scope: !7, file: !1, discriminator: 1)
> +!13 = distinct !{!13, !9}
> +!14 = !DILocation(line: 6, column: 1, scope: !7)
> +!15 = distinct !DISubprogram(name: "test2", scope: !1, file: !1, line: 8, type: !8, isLocal: false, isDefinition: true, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
> +!16 = !DILocation(line: 8, column: 14, scope: !15)
> +!17 = !DILocation(line: 11, column: 5, scope: !15)
> +!18 = !DILocation(line: 10, column: 3, scope: !15)
> +!19 = distinct !{!19, !16, !20}
> +!20 = !{!"llvm.loop.unroll.enable"}
> +!21 = !DILocation(line: 12, column: 1, scope: !15)
> +
> +; CHECK-NOT: !DICompileUnit
> +; CHECK-NOT: !DIFile
> +; CHECK-NOT: !DISubprogram
> +; CHECK-NOT: !DISubroutineType
> +; CHECK-NOT: !DILocation
> +; CHECK-NOT: !DILexicalBlockFile
> +; CHECK: [[LOOP]] = distinct !{[[LOOP]], [[LOOP_UNROLL:![0-9]+]]}
> +; CHECK-NEXT: [[LOOP_UNROLL]] = !{!"llvm.loop.unroll.enable"}
> +; CHECK-NOT: !DILocation
> Index: lib/IR/DebugInfo.cpp
> ===================================================================
> --- lib/IR/DebugInfo.cpp
> +++ lib/IR/DebugInfo.cpp
> @@ -239,13 +239,42 @@
>    return true;
>  }
>  
> +static llvm::MDNode *stripDebugLocFromLoopID(llvm::MDNode *N) {
> +  auto DebugLocOp =
> +      std::find_if(N->op_begin() + 1, N->op_end(), [](const MDOperand &Op) {
 
Can N->op_begin() == N->op_end() ever? If so, I think this is incorrect.
If not, maybe we should assert it?

> +        return isa<DILocation>(Op.get());
> +      });
> +
> +  // No debug location, we do not have to rewrite this MDNode.
> +  if (DebugLocOp == N->op_end())
> +    return N;
> +
> +  // There is only the debug location without any actual loop metadata, hence we
> +  // can remove the metadata.
> +  if (N->getNumOperands() == 2)
> +    return nullptr;
> +
> +  SmallVector<Metadata *, 4> Args;
> +  // Reserve operand 0 for loop id self reference.
> +  auto TempNode = MDNode::getTemporary(N->getContext(), None);
> +  Args.push_back(TempNode.get());
> +  Args.append(N->op_begin() + 1, DebugLocOp);
> +  Args.append(DebugLocOp + 1, N->op_end());
> +
> +  // Set the first operand to itself.
> +  MDNode *LoopID = MDNode::get(N->getContext(), Args);
> +  LoopID->replaceOperandWith(0, LoopID);
> +  return LoopID;
> +}
> +
>  bool llvm::stripDebugInfo(Function &F) {
>    bool Changed = false;
>    if (F.getSubprogram()) {
>      Changed = true;
>      F.setSubprogram(nullptr);
>    }
>  
> +  llvm::DenseMap<llvm::MDNode*, llvm::MDNode*> LoopIDsMap;
>    for (BasicBlock &BB : F) {
>      for (auto II = BB.begin(), End = BB.end(); II != End;) {
>        Instruction &I = *II++; // We may delete the instruction, increment now.
> @@ -259,6 +288,15 @@
>          I.setDebugLoc(DebugLoc());
>        }
>      }
> +
> +    auto *TermInst = BB.getTerminator();
> +    if (auto *LoopID = TermInst->getMetadata(LLVMContext::MD_loop)) {
> +      auto *NewLoopID = LoopIDsMap.lookup(LoopID);
> +      if (!NewLoopID)
> +        NewLoopID = LoopIDsMap[LoopID] = stripDebugLocFromLoopID(LoopID);
> +      if (NewLoopID != LoopID)
> +        TermInst->setMetadata(LLVMContext::MD_loop, NewLoopID);
> +    }
>    }
>    return Changed;
>  }
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