[llvm] [llvm-dwarfdump][LineCov 1/3] Add variable coverage metrics (PR #169646)

[Stephen Tozer via llvm-commits]

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@@ -0,0 +1,244 @@
+//===-- Coverage.cpp - Debug info coverage metrics ------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-dwarfdump.h"
+#include "llvm/BinaryFormat/Dwarf.h"
+#include "llvm/DebugInfo/DIContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h"
+#include "llvm/DebugInfo/DWARF/DWARFCompileUnit.h"
+#include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/DebugProgramInstruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IRReader/IRReader.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/SourceMgr.h"
+#include <set>
+
+using namespace llvm;
+using namespace llvm::dwarf;
+using namespace llvm::object;
+
+typedef std::pair<std::string, std::string> StringPair;
+
+static std::optional<std::set<std::pair<uint16_t, uint32_t>>>
+computeVariableCoverage(DWARFContext &DICtx, DWARFDie DIE,
+                        const DWARFDebugLine::LineTable *const LineTable) {
+  auto addLines = [](const DWARFDebugLine::LineTable *LineTable,
+                     std::set<std::pair<uint16_t, uint32_t>> &Lines,
+                     DWARFAddressRange Range,
+                     std::map<std::string, uint16_t, std::less<>> &FileNames) {
+    std::vector<uint32_t> Rows;
+    if (LineTable->lookupAddressRange({Range.LowPC, Range.SectionIndex},
+                                      Range.HighPC - Range.LowPC, Rows)) {
+      for (const auto &RowI : Rows) {
+        const auto Row = LineTable->Rows[RowI];
+        if (Row.Address.Address < Range.LowPC)
+          continue;
+        const auto FileIndex = Row.File;
+
+        if (!any_of(FileNames,
+                    [FileIndex](auto &FN) { return FN.second == FileIndex; })) {
+          std::string Name;
+          LineTable->getFileNameByIndex(
+              FileIndex, "",
+              DILineInfoSpecifier::FileLineInfoKind::RelativeFilePath, Name);
+          FileNames.emplace(Name, FileIndex);
+        }
+
+        const auto Line = Row.Line;
+        if (Line) // ignore zero lines
+          Lines.insert({FileIndex, Line});
+      }
+    }
+  };
+
+  std::map<std::string, uint16_t, std::less<>> FileNames;
+
+  auto Locations = DIE.getLocations(DW_AT_location);
+  std::optional<std::set<std::pair<uint16_t, uint32_t>>> Lines;
+  if (Locations) {
+    for (const auto &L : Locations.get()) {
+      if (L.Range) {
+        if (!Lines)
+          Lines = {{}};
+        addLines(LineTable, *Lines, L.Range.value(), FileNames);
+      }
+    }
+  } else {
+    consumeError(Locations.takeError());
+  }
+
+  auto Ranges = DIE.getParent().getAddressRanges();
+  std::optional<std::set<std::pair<uint16_t, uint32_t>>> ParentLines;
+  if (Ranges) {
+    ParentLines = {{}};
+    for (const auto &R : Ranges.get())
+      addLines(LineTable, *ParentLines, R, FileNames);
+  } else {
+    consumeError(Ranges.takeError());
+  }
+
+  if (!Lines && ParentLines) {
+    Lines = ParentLines;
+  } else if (ParentLines) {
+    std::set<std::pair<uint16_t, uint32_t>> Intersection;
+    std::set_intersection(Lines->begin(), Lines->end(), ParentLines->begin(),
+                          ParentLines->end(),
+                          std::inserter(Intersection, Intersection.begin()));
+    Lines = Intersection;
+  }
+
+  return Lines;
+}
+
+static const SmallVector<DWARFDie> getParentSubroutines(DWARFDie DIE) {
+  SmallVector<DWARFDie> Parents;
+  DWARFDie Parent = DIE;
+  do
+    if (Parent.getTag() == DW_TAG_subprogram ||
+        Parent.getTag() == DW_TAG_inlined_subroutine)
+      Parents.push_back(Parent);
+  while ((Parent = Parent.getParent()));
----------------
SLTozer wrote:

```suggestion
  do {
    if (Parent.getTag() == DW_TAG_subprogram ||
        Parent.getTag() == DW_TAG_inlined_subroutine)
      Parents.push_back(Parent);
  } while ((Parent = Parent.getParent()));
```
Would definitely suggest using braces for the do while.

https://github.com/llvm/llvm-project/pull/169646