Reset PAL metadata when AMDGPU traget stream finishes

[s-perron]

Summary

If the same stream object is used for multiple compiles, the PAL metadata from eariler compilations will leak into later one. See https://github.com/GPUOpen-Drivers/llpc/issues/882 for how this is happening in LLPC.

No tests were added because multiple compiles will have to happen using the same pass manager, and I do not see a setup for that on the LLVM side. Let me know if there is a good way to test this.

[dstuttard]

LGTM (minor comment typo), but I'm adding Tim who did most of the original code I think.

llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUTargetStreamer.cpp

177

its?

442

its?

[s-perron]

Fix typo in comment

[nhaehnle]

LGTM minus something rather obvious.

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp

581 ↗

(On Diff #285680)

Looks like some unrelated change got into this patch? (FWIW, I usually do arc diff @^ as part of a git rebase -i -- maybe newer versions of arc can do something smarter, I haven't reevaluated my workflow in some time)

[s-perron]

Remove unrelated changes

llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUTargetStreamer.cpp

 //===----------------------------------------------------------------------===//
 
 AMDGPUTargetAsmStreamer::AMDGPUTargetAsmStreamer(MCStreamer &S,
                                                  formatted_raw_ostream &OS)
     : AMDGPUTargetStreamer(S), OS(OS) { }
 
 // A hook for emitting stuff at the end.
 // We use it for emitting the accumulated PAL metadata as directives.
+// The PAL metadata is reset after it is emitted.
 void AMDGPUTargetAsmStreamer::finish() {
   std::string S;
   getPALMetadata()->toString(S);
   OS << S;
+
+  // Reset the pal metadata so its data will not affect a compilation that
+  // reuses this object.
+  getPALMetadata()->reset();
 }
 
 void AMDGPUTargetAsmStreamer::EmitDirectiveAMDGCNTarget(StringRef Target) {
   OS << "\t.amdgcn_target \"" << Target << "\"\n";
 }
 
 void AMDGPUTargetAsmStreamer::EmitDirectiveHSACodeObjectVersion(
     uint32_t Major, uint32_t Minor) {

 }
 
 MCELFStreamer &AMDGPUTargetELFStreamer::getStreamer() {
   return static_cast<MCELFStreamer &>(Streamer);
 }
 
 // A hook for emitting stuff at the end.
 // We use it for emitting the accumulated PAL metadata as a .note record.
+// The PAL metadata is reset after it is emitted.
 void AMDGPUTargetELFStreamer::finish() {
   std::string Blob;
   const char *Vendor = getPALMetadata()->getVendor();
   unsigned Type = getPALMetadata()->getType();
   getPALMetadata()->toBlob(Type, Blob);
   if (Blob.empty())
     return;
   EmitNote(Vendor, MCConstantExpr::create(Blob.size(), getContext()), Type,
            [&](MCELFStreamer &OS) { OS.emitBytes(Blob); });
+
+  // Reset the pal metadata so its data will not affect a compilation that
+  // reuses this object.
+  getPALMetadata()->reset();
 }
 
 void AMDGPUTargetELFStreamer::EmitNote(
     StringRef Name, const MCExpr *DescSZ, unsigned NoteType,
     function_ref<void(MCELFStreamer &)> EmitDesc) {
   auto &S = getStreamer();
   auto &Context = S.getContext();
 

llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.h

public:
   void toBlob(unsigned Type, std::string &S);
 
   // Get the msgpack::Document for the PAL metadata.
   msgpack::Document *getMsgPackDoc() { return &MsgPackDoc; }
 
   // Set legacy PAL metadata format.
   void setLegacy();
 
+  // Erase all PAL metadata.
+  void reset();
+
 private:
   // Return whether the blob type is legacy PAL metadata.
   bool isLegacy() const;
 
   // Reference (create if necessary) the node for the registers map.
   msgpack::DocNode &refRegisters();
 
   // Get (create if necessary) the registers map.

llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.cpp

bool AMDGPUPALMetadata::isLegacy() const {
   return BlobType == ELF::NT_AMD_AMDGPU_PAL_METADATA;
 }
 
 // Set legacy PAL metadata format.
 void AMDGPUPALMetadata::setLegacy() {
   BlobType = ELF::NT_AMD_AMDGPU_PAL_METADATA;
 }
 
+// Erase all PAL metadata.
+void AMDGPUPALMetadata::reset() {
+  MsgPackDoc.clear();
+  Registers = MsgPackDoc.getEmptyNode();
+  HwStages = MsgPackDoc.getEmptyNode();
+}