[AMDGPU] Add disassembler diagnostics for invalid kernel descriptors

llvm/docs/AMDGPUUsage.rst

@@ -4652,7 +4652,7 @@ The fields used by CP for code objects before V3 also match those specified in
                                                      entry point instruction
                                                      which must be 256 byte
                                                      aligned.
-     351:272 20                                      Reserved, must be 0.
+     351:192 20                                      Reserved, must be 0.
              bytes
      383:352 4 bytes COMPUTE_PGM_RSRC3               GFX6-GFX9
                                                        Reserved, must be 0.
@@ -5248,14 +5248,14 @@ The fields used by CP for code objects before V3 also match those specified in
      5:0     6 bits  ACCUM_OFFSET                    Offset of a first AccVGPR in the unified register file. Granularity 4.
                                                      Value 0-63. 0 - accum-offset = 4, 1 - accum-offset = 8, ...,
                                                      63 - accum-offset = 256.
-     6:15    10                                      Reserved, must be 0.
+     15:6    10                                      Reserved, must be 0.
              bits
      16      1 bit   TG_SPLIT                        - If 0 the waves of a work-group are
                                                        launched in the same CU.
                                                      - If 1 the waves of a work-group can be
                                                        launched in different CUs. The waves
                                                        cannot use S_BARRIER or LDS.
-     17:31   15                                      Reserved, must be 0.
+     31:17   15                                      Reserved, must be 0.
              bits
      32      **Total size 4 bytes.**
      ======= ===================================================================================================================

llvm/include/llvm/MC/MCDisassembler/MCDisassembler.h

@@ -12,6 +12,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/XCOFF.h"
 #include "llvm/MC/MCDisassembler/MCSymbolizer.h"
+#include "llvm/Support/Error.h"
 #include <cstdint>
 #include <memory>
 #include <vector>
@@ -139,28 +140,26 @@ class MCDisassembler {
   /// start of a symbol, or the entire symbol.
   /// This is used for example by WebAssembly to decode preludes.
   ///
-  /// Base implementation returns std::nullopt. So all targets by default ignore
-  /// to treat symbols separately.
+  /// Base implementation returns false. So all targets by default decline to
+  /// treat symbols separately.
   ///
   /// \param Symbol   - The symbol.
   /// \param Size     - The number of bytes consumed.
   /// \param Address  - The address, in the memory space of region, of the first
   ///                   byte of the symbol.
   /// \param Bytes    - A reference to the actual bytes at the symbol location.
-  /// \param CStream  - The stream to print comments and annotations on.
-  /// \return         - MCDisassembler::Success if bytes are decoded
-  ///                   successfully. Size must hold the number of bytes that
-  ///                   were decoded.
-  ///                 - MCDisassembler::Fail if the bytes are invalid. Size
-  ///                   must hold the number of bytes that were decoded before
-  ///                   failing. The target must print nothing. This can be
-  ///                   done by buffering the output if needed.
-  ///                 - std::nullopt if the target doesn't want to handle the
-  ///                   symbol separately. Value of Size is ignored in this
-  ///                   case.
-  virtual std::optional<DecodeStatus>
-  onSymbolStart(SymbolInfoTy &Symbol, uint64_t &Size, ArrayRef<uint8_t> Bytes,
-                uint64_t Address, raw_ostream &CStream) const;
+  /// \return         - True if this symbol triggered some target specific
+  ///                   disassembly for this symbol. Size must be set with the
+  ///                   number of bytes consumed.
+  ///                 - Error if this symbol triggered some target specific
+  ///                   disassembly for this symbol, but an error was found with
+  ///                   it. Size must be set with the number of bytes consumed.
+  ///                 - False if the target doesn't want to handle the symbol
+  ///                   separately. The value of Size is ignored in this case,
+  ///                   and Err must not be set.
+  virtual Expected<bool> onSymbolStart(SymbolInfoTy &Symbol, uint64_t &Size,
+                                       ArrayRef<uint8_t> Bytes,
+                                       uint64_t Address) const;
   // TODO:
   // Implement similar hooks that can be used at other points during
   // disassembly. Something along the following lines:

llvm/lib/MC/MCDisassembler/MCDisassembler.cpp

@@ -13,11 +13,11 @@ using namespace llvm;
 
 MCDisassembler::~MCDisassembler() = default;
 
-std::optional<MCDisassembler::DecodeStatus>
-MCDisassembler::onSymbolStart(SymbolInfoTy &Symbol, uint64_t &Size,
-                              ArrayRef<uint8_t> Bytes, uint64_t Address,
-                              raw_ostream &CStream) const {
-  return std::nullopt;
+Expected<bool> MCDisassembler::onSymbolStart(SymbolInfoTy &Symbol,
+                                             uint64_t &Size,
+                                             ArrayRef<uint8_t> Bytes,
+                                             uint64_t Address) const {
+  return false;
 }
 
 uint64_t MCDisassembler::suggestBytesToSkip(ArrayRef<uint8_t> Bytes,