Revert "[DLCov] Implement DebugLoc coverage tracking (llvm#107279)"

This reverts commit a9d93ec.

Reverted due to the commit including a config in LLVM headers that is not
available outside of the llvm source tree.

Author: SLTozer

clang/lib/CodeGen/BackendUtil.cpp

@@ -961,22 +961,6 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
       Debugify.setOrigDIVerifyBugsReportFilePath(
           CodeGenOpts.DIBugsReportFilePath);
     Debugify.registerCallbacks(PIC, MAM);
-
-#if ENABLE_DEBUGLOC_COVERAGE_TRACKING
-    // If we're using debug location coverage tracking, mark all the
-    // instructions coming out of the frontend without a DebugLoc as being
-    // compiler-generated, to prevent both those instructions and new
-    // instructions that inherit their location from being treated as
-    // incorrectly empty locations.
-    for (Function &F : *TheModule) {
-      if (!F.getSubprogram())
-        continue;
-      for (BasicBlock &BB : F)
-        for (Instruction &I : BB)
-          if (!I.getDebugLoc())
-            I.setDebugLoc(DebugLoc::getCompilerGenerated());
-    }
-#endif
   }
   // Attempt to load pass plugins and register their callbacks with PB.
   for (auto &PluginFN : CodeGenOpts.PassPlugins) {

llvm/docs/HowToUpdateDebugInfo.rst

@@ -169,47 +169,6 @@ See the discussion in the section about
 :ref:`merging locations<WhenToMergeLocation>` for examples of when the rule for
 dropping locations applies.
 
-.. _NewInstLocations:
-
-Setting locations for new instructions
---------------------------------------
-
-Whenever a new instruction is created and there is no suitable location for that
-instruction, that instruction should be annotated accordingly. There are a set
-of special ``DebugLoc`` values that can be set on an instruction to annotate the
-reason that it does not have a valid location. These are as follows:
-
-* ``DebugLoc::getCompilerGenerated()``: This indicates that the instruction is a
-  compiler-generated instruction, i.e. it is not associated with any user source
-  code.
-
-* ``DebugLoc::getDropped()``: This indicates that the instruction has
-  intentionally had its source location removed, according to the rules for
-  :ref:`dropping locations<WhenToDropLocation>`; this is set automatically by
-  ``Instruction::dropLocation()``.
-
-* ``DebugLoc::getUnknown()``: This indicates that the instruction does not have
-  a known or currently knowable source location, e.g. that it is infeasible to
-  determine the correct source location, or that the source location is
-  ambiguous in a way that LLVM cannot currently represent.
-
-* ``DebugLoc::getTemporary()``: This is used for instructions that we don't
-  expect to be emitted (e.g. ``UnreachableInst``), and so should not need a
-  valid location; if we ever try to emit a temporary location into an object/asm
-  file, this indicates that something has gone wrong.
-
-Where applicable, these should be used instead of leaving an instruction without
-an assigned location or explicitly setting the location as ``DebugLoc()``.
-Ordinarily these special locations are identical to an absent location, but LLVM
-built with coverage-tracking
-(``-DLLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING="COVERAGE"``) will keep track of
-these special locations in order to detect unintentionally-missing locations;
-for this reason, the most important rule is to *not* apply any of these if it
-isn't clear which, if any, is appropriate - an absent location can be detected
-and fixed, while an incorrectly annotated instruction is much harder to detect.
-On the other hand, if any of these clearly apply, then they should be used to
-prevent false positives from being flagged up.
-
 Rules for updating debug values
 ===============================
 

llvm/include/llvm/IR/DebugLoc.h

@@ -14,7 +14,6 @@
 #ifndef LLVM_IR_DEBUGLOC_H
 #define LLVM_IR_DEBUGLOC_H
 
-#include "llvm/Config/config.h"
 #include "llvm/IR/TrackingMDRef.h"
 #include "llvm/Support/DataTypes.h"
 
@@ -23,73 +22,6 @@ namespace llvm {
   class LLVMContext;
   class raw_ostream;
   class DILocation;
-  class Function;
-
-#if ENABLE_DEBUGLOC_COVERAGE_TRACKING
-  // Used to represent different "kinds" of DebugLoc, expressing that the
-  // instruction it is part of is either normal and should contain a valid
-  // DILocation, or otherwise describing the reason why the instruction does
-  // not contain a valid DILocation.
-  enum class DebugLocKind : uint8_t {
-    // The instruction is expected to contain a valid DILocation.
-    Normal,
-    // The instruction is compiler-generated, i.e. it is not associated with any
-    // line in the original source.
-    CompilerGenerated,
-    // The instruction has intentionally had its source location removed,
-    // typically because it was moved outside of its original control-flow and
-    // presenting the prior source location would be misleading for debuggers
-    // or profilers.
-    Dropped,
-    // The instruction does not have a known or currently knowable source
-    // location, e.g. the attribution is ambiguous in a way that can't be
-    // represented, or determining the correct location is complicated and
-    // requires future developer effort.
-    Unknown,
-    // DebugLoc is attached to an instruction that we don't expect to be
-    // emitted, and so can omit a valid DILocation; we don't expect to ever try
-    // and emit these into the line table, and trying to do so is a sign that
-    // something has gone wrong (most likely a DebugLoc leaking from a transient
-    // compiler-generated instruction).
-    Temporary
-  };
-
-  // Extends TrackingMDNodeRef to also store a DebugLocKind, allowing Debugify
-  // to ignore intentionally-empty DebugLocs.
-  class DILocAndCoverageTracking : public TrackingMDNodeRef {
-  public:
-    DebugLocKind Kind;
-    // Default constructor for empty DebugLocs.
-    DILocAndCoverageTracking()
-        : TrackingMDNodeRef(nullptr), Kind(DebugLocKind::Normal) {}
-    // Valid or nullptr MDNode*, normal DebugLocKind.
-    DILocAndCoverageTracking(const MDNode *Loc)
-        : TrackingMDNodeRef(const_cast<MDNode *>(Loc)),
-          Kind(DebugLocKind::Normal) {}
-    DILocAndCoverageTracking(const DILocation *Loc);
-    // Explicit DebugLocKind, which always means a nullptr MDNode*.
-    DILocAndCoverageTracking(DebugLocKind Kind)
-        : TrackingMDNodeRef(nullptr), Kind(Kind) {}
-  };
-  template <> struct simplify_type<DILocAndCoverageTracking> {
-    using SimpleType = MDNode *;
-
-    static MDNode *getSimplifiedValue(DILocAndCoverageTracking &MD) {
-      return MD.get();
-    }
-  };
-  template <> struct simplify_type<const DILocAndCoverageTracking> {
-    using SimpleType = MDNode *;
-
-    static MDNode *getSimplifiedValue(const DILocAndCoverageTracking &MD) {
-      return MD.get();
-    }
-  };
-
-  using DebugLocTrackingRef = DILocAndCoverageTracking;
-#else
-  using DebugLocTrackingRef = TrackingMDNodeRef;
-#endif // ENABLE_DEBUGLOC_COVERAGE_TRACKING
 
   /// A debug info location.
   ///
@@ -99,8 +31,7 @@ namespace llvm {
   /// To avoid extra includes, \a DebugLoc doubles the \a DILocation API with a
   /// one based on relatively opaque \a MDNode pointers.
   class DebugLoc {
-
-    DebugLocTrackingRef Loc;
+    TrackingMDNodeRef Loc;
 
   public:
     DebugLoc() = default;
@@ -116,31 +47,6 @@ namespace llvm {
     /// IR.
     explicit DebugLoc(const MDNode *N);
 
-#if ENABLE_DEBUGLOC_COVERAGE_TRACKING
-    DebugLoc(DebugLocKind Kind) : Loc(Kind) {}
-    DebugLocKind getKind() const { return Loc.Kind; }
-#endif
-
-#if ENABLE_DEBUGLOC_COVERAGE_TRACKING
-    static inline DebugLoc getTemporary() {
-      return DebugLoc(DebugLocKind::Temporary);
-    }
-    static inline DebugLoc getUnknown() {
-      return DebugLoc(DebugLocKind::Unknown);
-    }
-    static inline DebugLoc getCompilerGenerated() {
-      return DebugLoc(DebugLocKind::CompilerGenerated);
-    }
-    static inline DebugLoc getDropped() {
-      return DebugLoc(DebugLocKind::Dropped);
-    }
-#else
-    static inline DebugLoc getTemporary() { return DebugLoc(); }
-    static inline DebugLoc getUnknown() { return DebugLoc(); }
-    static inline DebugLoc getCompilerGenerated() { return DebugLoc(); }
-    static inline DebugLoc getDropped() { return DebugLoc(); }
-#endif // ENABLE_DEBUGLOC_COVERAGE_TRACKING
-
     /// Get the underlying \a DILocation.
     ///
     /// \pre !*this or \c isa<DILocation>(getAsMDNode()).

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -2098,10 +2098,6 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
   }
 
   if (!DL) {
-    // FIXME: We could assert that `DL.getKind() != DebugLocKind::Temporary`
-    // here, or otherwise record any temporary DebugLocs seen to ensure that
-    // transient compiler-generated instructions aren't leaking their DLs to
-    // other instructions.
     // We have an unspecified location, which might want to be line 0.
     // If we have already emitted a line-0 record, don't repeat it.
     if (LastAsmLine == 0)

llvm/lib/IR/DebugInfo.cpp

@@ -987,10 +987,8 @@ void Instruction::updateLocationAfterHoist() { dropLocation(); }
 
 void Instruction::dropLocation() {
   const DebugLoc &DL = getDebugLoc();
-  if (!DL) {
-    setDebugLoc(DebugLoc::getDropped());
+  if (!DL)
     return;
-  }
 
   // If this isn't a call, drop the location to allow a location from a
   // preceding instruction to propagate.
@@ -1002,7 +1000,7 @@ void Instruction::dropLocation() {
   }
 
   if (!MayLowerToCall) {
-    setDebugLoc(DebugLoc::getDropped());
+    setDebugLoc(DebugLoc());
     return;
   }
 
@@ -1021,7 +1019,7 @@ void Instruction::dropLocation() {
     //
     // One alternative is to set a line 0 location with the existing scope and
     // inlinedAt info. The location might be sensitive to when inlining occurs.
-    setDebugLoc(DebugLoc::getDropped());
+    setDebugLoc(DebugLoc());
 }
 
 //===----------------------------------------------------------------------===//

llvm/lib/IR/DebugLoc.cpp

@@ -11,12 +11,6 @@
 #include "llvm/IR/DebugInfo.h"
 using namespace llvm;
 
-#if ENABLE_DEBUGLOC_COVERAGE_TRACKING
-DILocAndCoverageTracking::DILocAndCoverageTracking(const DILocation *L)
-    : TrackingMDNodeRef(const_cast<DILocation *>(L)),
-      Kind(DebugLocKind::Normal) {}
-#endif // ENABLE_DEBUGLOC_COVERAGE_TRACKING
-
 //===----------------------------------------------------------------------===//
 // DebugLoc Implementation
 //===----------------------------------------------------------------------===//

llvm/lib/Transforms/Utils/Debugify.cpp

@@ -290,16 +290,6 @@ bool llvm::stripDebugifyMetadata(Module &M) {
   return Changed;
 }
 
-bool hasLoc(const Instruction &I) {
-  const DILocation *Loc = I.getDebugLoc().get();
-#if ENABLE_DEBUGLOC_COVERAGE_TRACKING
-  DebugLocKind Kind = I.getDebugLoc().getKind();
-  return Loc || Kind != DebugLocKind::Normal;
-#else
-  return Loc;
-#endif
-}
-
 bool llvm::collectDebugInfoMetadata(Module &M,
                                     iterator_range<Module::iterator> Functions,
                                     DebugInfoPerPass &DebugInfoBeforePass,
@@ -372,7 +362,9 @@ bool llvm::collectDebugInfoMetadata(Module &M,
         LLVM_DEBUG(dbgs() << "  Collecting info for inst: " << I << '\n');
         DebugInfoBeforePass.InstToDelete.insert({&I, &I});
 
-        DebugInfoBeforePass.DILocations.insert({&I, hasLoc(I)});
+        const DILocation *Loc = I.getDebugLoc().get();
+        bool HasLoc = Loc != nullptr;
+        DebugInfoBeforePass.DILocations.insert({&I, HasLoc});
       }
     }
   }
@@ -615,7 +607,10 @@ bool llvm::checkDebugInfoMetadata(Module &M,
 
         LLVM_DEBUG(dbgs() << "  Collecting info for inst: " << I << '\n');
 
-        DebugInfoAfterPass.DILocations.insert({&I, hasLoc(I)});
+        const DILocation *Loc = I.getDebugLoc().get();
+        bool HasLoc = Loc != nullptr;
+
+        DebugInfoAfterPass.DILocations.insert({&I, HasLoc});
       }
     }
   }