[AMDGPU] Do not generate spurious PAL metadata

My previous fix rL356591 "[AMDGPU] Added MsgPack format PAL metadata"
accidentally caused a spurious PAL metadata .note record to be emitted
for any AMDGPU output. That caused failures in the lld test
amdgpu-relocs.s. Fixed.

Differential Revision: https://reviews.llvm.org/D59613

Change-Id: Ie04a2aaae890dcd490f22c89edf9913a77ce070e
llvm-svn: 356621

2 files changed, 10 insertions, 6 deletions

diff --git a/llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.cpp b/llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.cpp
index abd1c3e69cb..694f7c6dc75 100644
--- a/llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.cpp
+++ b/llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.cpp
@@ -518,6 +518,8 @@ static const char *getRegisterName(unsigned RegNum) {
 // Convert the accumulated PAL metadata into an asm directive.
 void AMDGPUPALMetadata::toString(std::string &String) {
   String.clear();
+  if (!BlobType)
+    return;
   raw_string_ostream Stream(String);
   if (isLegacy()) {
     if (MsgPackDoc.getRoot().getKind() == msgpack::Type::Nil)
@@ -564,11 +566,12 @@ void AMDGPUPALMetadata::toString(std::string &String) {
 }
 
 // Convert the accumulated PAL metadata into a binary blob for writing as
-// a .note record of the specified AMD type.
+// a .note record of the specified AMD type. Returns an empty blob if
+// there is no PAL metadata,
 void AMDGPUPALMetadata::toBlob(unsigned Type, std::string &Blob) {
   if (Type == ELF::NT_AMD_AMDGPU_PAL_METADATA)
     toLegacyBlob(Blob);
-  else
+  else if (Type)
     toMsgPackBlob(Blob);
 }
 
@@ -678,9 +681,10 @@ const char *AMDGPUPALMetadata::getVendor() const {
 
 // Get .note record type of metadata blob to be emitted:
 // ELF::NT_AMD_AMDGPU_PAL_METADATA (legacy key=val format), or
-// ELF::NT_AMDGPU_METADATA (MsgPack format).
+// ELF::NT_AMDGPU_METADATA (MsgPack format), or
+// 0 (no PAL metadata).
 unsigned AMDGPUPALMetadata::getType() const {
-  return BlobType ? BlobType : unsigned(ELF::NT_AMDGPU_METADATA);
+  return BlobType;
 }
 
 // Return whether the blob type is legacy PAL metadata.
diff --git a/llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.h b/llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.h
index e676c28da7b..dbef2cc605d 100644
--- a/llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.h
+++ b/llvm/lib/Target/AMDGPU/Utils/AMDGPUPALMetadata.h
@@ -92,8 +92,8 @@ public:
 
   // Get .note record type of metadata blob to be emitted:
   // ELF::NT_AMD_AMDGPU_PAL_METADATA (legacy key=val format), or
-  // ELF::NT_AMD_AMDGPU_PAL_METADATA_MSGPACK or ELF::NT_AMDGPU_METADATA
-  // (MsgPack format).
+  // ELF::NT_AMDGPU_METADATA (MsgPack format), or
+  // 0 (no PAL metadata).
   unsigned getType() const;
 
   // Emit the accumulated PAL metadata as a binary blob.