[COFF] Assign unique identifiers to ObjFiles from LTO

Use the unique filenames that are used when /lldsavetemps is passed.
After this change, module names for LTO blobs in PDBs will be unique.
Visual Studio and probably other debuggers expect module names to be
unique.

Revert some changes from 1e0b158db (2017) that are no longer necessary
after removing MSVC LTO support.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D78221

lld/COFF/LTO.cpp

@@ -144,7 +144,7 @@ void BitcodeCompiler::add(BitcodeFile &f) {
 
 // Merge all the bitcode files we have seen, codegen the result
 // and return the resulting objects.
-std::vector<StringRef> BitcodeCompiler::compile() {
+std::vector<InputFile *> BitcodeCompiler::compile() {
   unsigned maxTasks = ltoObj->getMaxTasks();
   buf.resize(maxTasks);
   files.resize(maxTasks);
@@ -188,22 +188,32 @@ std::vector<StringRef> BitcodeCompiler::compile() {
   if (!config->ltoCache.empty())
     pruneCache(config->ltoCache, config->ltoCachePolicy);
 
-  std::vector<StringRef> ret;
+  std::vector<InputFile *> ret;
   for (unsigned i = 0; i != maxTasks; ++i) {
-    if (buf[i].empty())
-      continue;
-    if (config->saveTemps) {
-      if (i == 0)
-        saveBuffer(buf[i], config->outputFile + ".lto.obj");
-      else
-        saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.obj");
-    }
-    ret.emplace_back(buf[i].data(), buf[i].size());
-  }
+    // Assign unique names to LTO objects. This ensures they have unique names
+    // in the PDB if one is produced. The names should look like:
+    // - foo.exe.lto.obj
+    // - foo.exe.lto.1.obj
+    // - ...
+    StringRef ltoObjName =
+        saver.save(Twine(config->outputFile) + ".lto" +
+                   (i == 0 ? Twine("") : Twine('.') + Twine(i)) + ".obj");
 
-  for (std::unique_ptr<MemoryBuffer> &file : files)
-    if (file)
-      ret.push_back(file->getBuffer());
+    // Get the native object contents either from the cache or from memory.  Do
+    // not use the cached MemoryBuffer directly, or the PDB will not be
+    // deterministic.
+    StringRef objBuf;
+    if (files[i])
+      objBuf = files[i]->getBuffer();
+    else
+      objBuf = buf[i];
+    if (objBuf.empty())
+      continue;
+
+    if (config->saveTemps)
+      saveBuffer(buf[i], ltoObjName);
+    ret.push_back(make<ObjFile>(MemoryBufferRef(objBuf, ltoObjName)));
+  }
 
   return ret;
 }

lld/COFF/LTO.h

@@ -45,7 +45,7 @@ public:
   ~BitcodeCompiler();
 
   void add(BitcodeFile &f);
-  std::vector<StringRef> compile();
+  std::vector<InputFile *> compile();
 
 private:
   std::unique_ptr<llvm::lto::LTO> ltoObj;

lld/COFF/SymbolTable.cpp

@@ -789,20 +789,16 @@ Symbol *SymbolTable::addUndefined(StringRef name) {
   return addUndefined(name, nullptr, false);
 }
 
-std::vector<StringRef> SymbolTable::compileBitcodeFiles() {
-  lto.reset(new BitcodeCompiler);
-  for (BitcodeFile *f : BitcodeFile::instances)
-    lto->add(*f);
-  return lto->compile();
-}
-
 void SymbolTable::addCombinedLTOObjects() {
   if (BitcodeFile::instances.empty())
     return;
 
   ScopedTimer t(ltoTimer);
-  for (StringRef object : compileBitcodeFiles()) {
-    auto *obj = make<ObjFile>(MemoryBufferRef(object, "lto.tmp"));
+  lto.reset(new BitcodeCompiler);
+  for (BitcodeFile *f : BitcodeFile::instances)
+    lto->add(*f);
+  for (InputFile *newObj : lto->compile()) {
+    ObjFile *obj = cast<ObjFile>(newObj);
     obj->parse();
     ObjFile::instances.push_back(obj);
   }

lld/COFF/SymbolTable.h

@@ -77,7 +77,6 @@ public:
   // BitcodeFiles and add them to the symbol table. Called after all files are
   // added and before the writer writes results to a file.
   void addCombinedLTOObjects();
-  std::vector<StringRef> compileBitcodeFiles();
 
   // Creates an Undefined symbol for a given name.
   Symbol *addUndefined(StringRef name);

lld/test/COFF/lto-parallel.ll

@@ -1,23 +1,35 @@
 ; REQUIRES: x86
 ; RUN: llvm-as -o %t.obj %s
-; RUN: lld-link -opt:noicf /out:%t.exe /entry:foo /include:bar /opt:lldltopartitions=2 /subsystem:console /lldmap:%t.map %t.obj
+; RUN: lld-link -opt:noicf /out:%t.exe /entry:foo /include:bar /opt:lldltopartitions=2 /subsystem:console /lldmap:%t.map %t.obj /debug /pdb:%t.pdb
 ; RUN: FileCheck %s < %t.map
+; RUN: llvm-pdbutil dump %t.pdb --modules | FileCheck %s --check-prefix=PDB
 
 target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-pc-windows-msvc"
 
-; CHECK: lto.tmp
-; CHECK: lto.tmp
+; CHECK: lto-parallel.ll.tmp.exe.lto.obj:
+; CHECK: lto-parallel.ll.tmp.exe.lto.obj:
 ; CHECK-NEXT: foo
 define void @foo() {
   call void @bar()
   ret void
 }
 
-; CHECK: lto.tmp
-; CHECK: lto.tmp
+; CHECK: lto-parallel.ll.tmp.exe.lto.1.obj:
+; CHECK: lto-parallel.ll.tmp.exe.lto.1.obj:
 ; CHECK: bar
 define void @bar() {
   call void @foo()
   ret void
 }
+
+
+; Objects in the PDB should receive distinct names.
+
+; PDB: Modules
+; PDB: Mod 0000 | `{{.*}}lto-parallel.ll.tmp.exe.lto.obj`:
+; PDB: Obj: `{{.*}}lto-parallel.ll.tmp.exe.lto.obj`:
+; PDB: Mod 0001 | `{{.*}}lto-parallel.ll.tmp.exe.lto.1.obj`:
+; PDB: Obj: `{{.*}}lto-parallel.ll.tmp.exe.lto.1.obj`:
+; PDB: Mod 0002 | `* Linker *`:
+; PDB: Obj: ``:

lld/test/COFF/pdb-thinlto.ll

@@ -0,0 +1,38 @@
+; REQUIRES: x86
+; RUN: rm -rf %t && mkdir -p %t && cd %t
+; RUN: opt -thinlto-bc -o main.bc %s
+; RUN: opt -thinlto-bc -o foo.bc %S/Inputs/lto-dep.ll
+
+; Even if the native object is cached, the PDB must be the same.
+; RUN: rm -rf thinltocachedir && mkdir thinltocachedir
+
+; RUN: lld-link /lldltocache:thinltocachedir /out:main.exe /entry:main /subsystem:console main.bc foo.bc /debug /pdb:main.pdb
+
+; RUN: llvm-pdbutil dump --modules main.pdb | FileCheck %s
+
+; Run again with the cache. Make sure we get the same object names.
+
+; RUN: lld-link /lldltocache:thinltocachedir /out:main.exe /entry:main /subsystem:console main.bc foo.bc /debug /pdb:main.pdb
+
+; RUN: llvm-pdbutil dump --modules main.pdb | FileCheck %s
+
+
+target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define i32 @main() {
+  call void @foo()
+  ret i32 0
+}
+
+declare void @foo()
+
+; CHECK:                           Modules
+; CHECK: ============================================================
+; CHECK: Mod 0000 | `{{.*}}main.exe.lto.obj`:
+; CHECK: Obj: `{{.*}}main.exe.lto.obj`:
+; CHECK: Mod 0001 | `{{.*}}main.exe.lto.1.obj`:
+; CHECK: Obj: `{{.*}}main.exe.lto.1.obj`:
+; CHECK: Mod 0002 | `{{.*}}main.exe.lto.2.obj`:
+; CHECK: Obj: `{{.*}}main.exe.lto.2.obj`:
+; CHECK: Mod 0003 | `* Linker *`:

lld/test/COFF/thinlto.ll

@@ -4,15 +4,15 @@
 ; RUN: opt -thinlto-bc -o %T/thinlto/main.obj %s
 ; RUN: opt -thinlto-bc -o %T/thinlto/foo.obj %S/Inputs/lto-dep.ll
 ; RUN: lld-link /lldsavetemps /out:%T/thinlto/main.exe /entry:main /subsystem:console %T/thinlto/main.obj %T/thinlto/foo.obj
-; RUN: llvm-nm %T/thinlto/main.exe1.lto.obj | FileCheck %s
+; RUN: llvm-nm %T/thinlto/main.exe.lto.1.obj | FileCheck %s
 
 ; Test various possible options for /opt:lldltojobs
 ; RUN: lld-link /lldsavetemps /out:%T/thinlto/main.exe /entry:main /subsystem:console %T/thinlto/main.obj %T/thinlto/foo.obj /opt:lldltojobs=1
-; RUN: llvm-nm %T/thinlto/main.exe1.lto.obj | FileCheck %s
+; RUN: llvm-nm %T/thinlto/main.exe.lto.1.obj | FileCheck %s
 ; RUN: lld-link /lldsavetemps /out:%T/thinlto/main.exe /entry:main /subsystem:console %T/thinlto/main.obj %T/thinlto/foo.obj /opt:lldltojobs=all
-; RUN: llvm-nm %T/thinlto/main.exe1.lto.obj | FileCheck %s
+; RUN: llvm-nm %T/thinlto/main.exe.lto.1.obj | FileCheck %s
 ; RUN: lld-link /lldsavetemps /out:%T/thinlto/main.exe /entry:main /subsystem:console %T/thinlto/main.obj %T/thinlto/foo.obj /opt:lldltojobs=100
-; RUN: llvm-nm %T/thinlto/main.exe1.lto.obj | FileCheck %s
+; RUN: llvm-nm %T/thinlto/main.exe.lto.1.obj | FileCheck %s
 ; RUN: not lld-link /lldsavetemps /out:%T/thinlto/main.exe /entry:main /subsystem:console %T/thinlto/main.obj %T/thinlto/foo.obj /opt:lldltojobs=foo 2>&1 | FileCheck %s --check-prefix=BAD-JOBS
 ; BAD-JOBS: error: /opt:lldltojobs: invalid job count: foo
 

lld/test/COFF/weak-external.test

@@ -5,8 +5,8 @@
 # RUN: lld-link /out:%t2.exe /entry:g /subsystem:console /lldmap:%t2.map %t.obj %t.lto.obj
 # RUN: FileCheck %s < %t2.map
 
-# CHECK: lto.tmp
-# CHECK-NEXT: lto.tmp
+# CHECK:      .lto.obj:
+# CHECK-NEXT: .lto.obj:
 # CHECK-NEXT: 0 g
 
 --- !COFF

lld/test/COFF/weak-external3.test

@@ -6,8 +6,8 @@
 # RUN: lld-link /out:%t2.exe /entry:f /subsystem:console /lldmap:%t2.map %t.obj %t.lto.obj
 # RUN: FileCheck --check-prefix=CHECK2 %s < %t2.map
 
-# CHECK1: lto.tmp
-# CHECK1: lto.tmp
+# CHECK1:      .lto.obj:
+# CHECK1-NEXT: .lto.obj:
 # CHECK1-NEXT: 0 g
 
 # CHECK2: weak-external3.test.tmp.obj