[WebAssembly] Change indices types to unsined int (NFC)

[aheejin]

Summary

This changes int types to unsigned int in a few places: function indices
and [[ https://github.com/llvm-mirror/llvm/blob/088dcea9b165b0e5929d0fc89dfc1200dc3912f1/include/llvm/BinaryFormat/Wasm.h#L265-L273 | wasm::Valtype ]] (which is unsigend int enum). Currently these
values cannot have negative values anyway, so this should not be a
functional change for now.

lib/MC/WasmObjectWriter.cpp

struct WasmFunctionTypeDenseMapInfo {
   static WasmFunctionType getTombstoneKey() {
     WasmFunctionType FuncTy;
     FuncTy.State = WasmFunctionType::Tombstone;
     return FuncTy;
   }
   static unsigned getHashValue(const WasmFunctionType &FuncTy) {
     uintptr_t Value = FuncTy.State;
     for (wasm::ValType Ret : FuncTy.Returns)
-      Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Ret));
+      Value += DenseMapInfo<uint32_t>::getHashValue(uint32_t(Ret));
     for (wasm::ValType Param : FuncTy.Params)
-      Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Param));
+      Value += DenseMapInfo<uint32_t>::getHashValue(uint32_t(Param));
     return Value;
   }
   static bool isEqual(const WasmFunctionType &LHS,
                       const WasmFunctionType &RHS) {
     return LHS == RHS;
   }
 };
 
 // A wasm data segment.  A wasm binary contains only a single data section
 // but that can contain many segments, each with their own virtual location
 // in memory.  Each MCSection data created by llvm is modeled as its own
 // wasm data segment.
 struct WasmDataSegment {
   MCSectionWasm *Section;
   StringRef Name;
   uint32_t Offset;
   uint32_t Alignment;
   uint32_t Flags;
   SmallVector<char, 4> Data;
 };
 
 // A wasm function to be written into the function section.
 struct WasmFunction {
-  int32_t Type;
+  uint32_t Type;
   const MCSymbolWasm *Sym;
 };
 
 // A wasm global to be written into the global section.
 struct WasmGlobal {
   wasm::WasmGlobalType Type;
   uint64_t InitialValue;
 };
class WasmObjectWriter : public MCObjectWriter {
   std::vector<WasmCustomSection> CustomSections;
   // Relocations for fixing up references in the custom sections.
   DenseMap<const MCSectionWasm *, std::vector<WasmRelocationEntry>>
       CustomSectionsRelocations;
 
   // Map from section to defining function symbol.
   DenseMap<const MCSection *, const MCSymbol *> SectionFunctions;
 
-  DenseMap<WasmFunctionType, int32_t, WasmFunctionTypeDenseMapInfo>
+  DenseMap<WasmFunctionType, uint32_t, WasmFunctionTypeDenseMapInfo>
       FunctionTypeIndices;
   SmallVector<WasmFunctionType, 4> FunctionTypes;
   SmallVector<WasmGlobal, 4> Globals;
   SmallVector<WasmDataSegment, 4> DataSegments;
   unsigned NumFunctionImports = 0;
   unsigned NumGlobalImports = 0;
   uint32_t SectionCount = 0;