[WebAssembly] Improve logging and comments around relocations. NFC.

[ncw]

Looks harmless.

lld/trunk/wasm/InputChunks.cpp

 #define DEBUG_TYPE "lld"
 
 using namespace llvm;
 using namespace llvm::wasm;
 using namespace llvm::support::endian;
 using namespace lld;
 using namespace lld::wasm;
 
+StringRef ReloctTypeToString(uint8_t RelocType) {
+  switch (RelocType) {
+#define WASM_RELOC(NAME, REL) case REL: return #NAME;
+#include "llvm/BinaryFormat/WasmRelocs.def"
+#undef WASM_RELOC
+  }
+  llvm_unreachable("unknown reloc type");
+}
+
 std::string lld::toString(const InputChunk *C) {
   return (toString(C->File) + ":(" + C->getName() + ")").str();
 }
 
 void InputChunk::copyRelocations(const WasmSection &Section) {
   if (Section.Relocations.empty())
     return;
   size_t Start = getInputSectionOffset();
   size_t Size = getSize();
   for (const WasmRelocation &R : Section.Relocations)
     if (R.Offset >= Start && R.Offset < Start + Size)
       Relocations.push_back(R);
 }
 
 // Copy this input chunk to an mmap'ed output file and apply relocations.
 void InputChunk::writeTo(uint8_t *Buf) const {
   // Copy contents
   memcpy(Buf + OutputOffset, data().data(), data().size());
 
   // Apply relocations
   if (Relocations.empty())
     return;
 
-  DEBUG(dbgs() << "applyRelocations: count=" << Relocations.size() << "\n");
+  DEBUG(dbgs() << "applying relocations: count=" << Relocations.size() << "\n");
   int32_t Off = OutputOffset - getInputSectionOffset();
 
   for (const WasmRelocation &Rel : Relocations) {
     uint8_t *Loc = Buf + Rel.Offset + Off;
-    uint64_t Value = File->calcNewValue(Rel);
-
-    DEBUG(dbgs() << "write reloc: type=" << Rel.Type << " index=" << Rel.Index
+    uint32_t Value = File->calcNewValue(Rel);
+    DEBUG(dbgs() << "apply reloc: type=" << ReloctTypeToString(Rel.Type)
+                 << " addend=" << Rel.Addend << " index=" << Rel.Index
                  << " value=" << Value << " offset=" << Rel.Offset << "\n");
 
     switch (Rel.Type) {
     case R_WEBASSEMBLY_TYPE_INDEX_LEB:
     case R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
     case R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
     case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
       encodeULEB128(Value, Loc, 5);

lld/trunk/wasm/InputFiles.cpp

 
 void ObjFile::dumpInfo() const {
   log("info for: " + getName() +
       "\n              Symbols : " + Twine(Symbols.size()) +
       "\n     Function Imports : " + Twine(WasmObj->getNumImportedFunctions()) +
       "\n       Global Imports : " + Twine(WasmObj->getNumImportedGlobals()));
 }
 
-// Relocations contain an index into the function, global or table index
-// space of the input file.  This function takes a relocation and returns the
-// relocated index (i.e. translates from the input index space to the output
-// index space).
+// Relocations contain either symbol or type indices.  This function takes a
+// relocation and returns relocated index (i.e. translates from the input
+// sybmol/type space to the output symbol/type space).
 uint32_t ObjFile::calcNewIndex(const WasmRelocation &Reloc) const {
   if (Reloc.Type == R_WEBASSEMBLY_TYPE_INDEX_LEB) {
     assert(TypeIsUsed[Reloc.Index]);
     return TypeMap[Reloc.Index];
   }
   return Symbols[Reloc.Index]->getOutputSymbolIndex();
 }