[LLD][COFF] Support finding pdb files from outputpath (llvm#94153)

In addition to looking for dependent (input) PDB files next to the associated .OBJ file, we now also look into the output folder as well. This mimics MSVC link.exe behavior.

Fixes llvm#94152

lld/COFF/InputFiles.cpp

@@ -818,19 +818,6 @@ void ObjFile::initializeDependencies() {
  debugTypesObj = makeTpiSource(ctx, this);
 }
 
-// Make a PDB path assuming the PDB is in the same folder as the OBJ
-static std::string getPdbBaseName(ObjFile *file, StringRef tSPath) {
- StringRef localPath =
- !file->parentName.empty() ? file->parentName : file->getName();
- SmallString<128> path = sys::path::parent_path(localPath);
-
- // Currently, type server PDBs are only created by MSVC cl, which only runs
- // on Windows, so we can assume type server paths are Windows style.
- sys::path::append(path,
- sys::path::filename(tSPath, sys::path::Style::windows));
- return std::string(path);
-}
-
 // The casing of the PDB path stamped in the OBJ can differ from the actual path
 // on disk. With this, we ensure to always use lowercase as a key for the
 // pdbInputFileInstances map, at least on Windows.
@@ -843,17 +830,35 @@ static std::string normalizePdbPath(StringRef path) {
 }
 
 // If existing, return the actual PDB path on disk.
-static std::optional<std::string> findPdbPath(StringRef pdbPath,
- ObjFile *dependentFile) {
+static std::optional<std::string>
+findPdbPath(StringRef pdbPath, ObjFile *dependentFile, StringRef outputPath) {
  // Ensure the file exists before anything else. In some cases, if the path
  // points to a removable device, Driver::enqueuePath() would fail with an
  // error (EAGAIN, "resource unavailable try again") which we want to skip
  // silently.
  if (llvm::sys::fs::exists(pdbPath))
  return normalizePdbPath(pdbPath);
- std::string ret = getPdbBaseName(dependentFile, pdbPath);
- if (llvm::sys::fs::exists(ret))
- return normalizePdbPath(ret);
+
+ StringRef objPath = !dependentFile->parentName.empty()
+ ? dependentFile->parentName
+ : dependentFile->getName();
+
+ // Currently, type server PDBs are only created by MSVC cl, which only runs
+ // on Windows, so we can assume type server paths are Windows style.
+ StringRef pdbName = sys::path::filename(pdbPath, sys::path::Style::windows);
+
+ // Check if the PDB is in the same folder as the OBJ.
+ SmallString<128> path;
+ sys::path::append(path, sys::path::parent_path(objPath), pdbName);
+ if (llvm::sys::fs::exists(path))
+ return normalizePdbPath(path);
+
+ // Check if the PDB is in the output folder.
+ path.clear();
+ sys::path::append(path, sys::path::parent_path(outputPath), pdbName);
+ if (llvm::sys::fs::exists(path))
+ return normalizePdbPath(path);
+
  return std::nullopt;
 }
 
@@ -865,7 +870,7 @@ PDBInputFile::~PDBInputFile() = default;
 PDBInputFile *PDBInputFile::findFromRecordPath(const COFFLinkerContext &ctx,
  StringRef path,
  ObjFile *fromFile) {
- auto p = findPdbPath(path.str(), fromFile);
+ auto p = findPdbPath(path.str(), fromFile, ctx.config.outputFile);
  if (!p)
  return nullptr;
  auto it = ctx.pdbInputFileInstances.find(*p);
@@ -931,7 +936,7 @@ std::optional<DILineInfo> ObjFile::getDILineInfo(uint32_t offset,
 }
 
 void ObjFile::enqueuePdbFile(StringRef path, ObjFile *fromFile) {
- auto p = findPdbPath(path.str(), fromFile);
+ auto p = findPdbPath(path.str(), fromFile, ctx.config.outputFile);
  if (!p)
  return;
  auto it = ctx.pdbInputFileInstances.emplace(*p, nullptr);

lld/test/COFF/pdb-type-server-simple.test

@@ -27,6 +27,10 @@ Re-run with /DEBUG:GHASH
 RUN: lld-link a.obj b.obj -entry:main -debug:ghash -out:t.exe -pdb:t.pdb -nodefaultlib -summary -verbose
 RUN: llvm-pdbutil dump -symbols -types -ids -globals %t/t.pdb | FileCheck %s
 
+Re-run with pdb from outputpath
+RUN: mkdir -p libs
+RUN: cp a.obj libs/a.obj && cp b.obj libs/b.obj
+RUN: lld-link libs/a.obj libs/b.obj -entry:main -debug:ghash -out:t.exe -pdb:t.pdb -nodefaultlib -summary 2>&1 | FileCheck %s -check-prefix FAILURE-MISSING-PDBFILE
 
 CHECK-LABEL: Types (TPI Stream)
 CHECK: ============================================================
@@ -125,3 +129,6 @@ SUMMARY-NEXT: index total bytes count size
 SUMMARY-NEXT: 0x1006: 256 = 1 * 256
 SUMMARY: Run llvm-pdbutil to print details about a particular record:
 SUMMARY-NEXT: llvm-pdbutil dump -ids -id-index 0x1006 t.pdb
+
+FAILURE-MISSING-PDBFILE-NOT: Cannot use debug info for '{{.*}}.obj'
+FAILURE-MISSING-PDBFILE-NOT: failed to load reference '{{.*}}.pdb': no such file or directory