[WebAssembly] Fix bug where reloc addends were written as unsigned

[sbc100]

Summary

relocation addends can be negative so should be written as
signed LEBs. This bug meant that writing value between 64
and 128 would be incorrectly interpreted as negative by the
object file readers.

[sbc100]

whitespace

lld/trunk/test/wasm/reloc-addend.ll

+; RUN: llc -filetype=obj %s -o %t.o
+; RUN: wasm-ld --check-signatures -r -o %t.wasm %t.o
+; RUN: obj2yaml %t.wasm | FileCheck %s
+
+target triple = "wasm32-unknown-unknown-wasm"
+
+@foo = hidden global [76 x i32] zeroinitializer, align 16
+
+; bar points to the 16th element, which happens to be 64 bytes
+; This generates an addend of 64 which, is the value at which
+; signed and unsigned LEB encodes will differ.
+@bar = hidden local_unnamed_addr global i32* getelementptr inbounds ([76 x i32], [76 x i32]* @foo, i32 0, i32 16), align 4
+
+; CHECK:        - Type:            DATA
+; CHECK-NEXT:     Relocations:     
+; CHECK-NEXT:       - Type:            R_WEBASSEMBLY_MEMORY_ADDR_I32
+; CHECK-NEXT:         Index:           0
+; CHECK-NEXT:         Offset:          0x0000013D
+; CHECK-NEXT:         Addend:          64

lld/trunk/wasm/InputChunks.cpp

for (const WasmRelocation &Rel : Relocations) {
     writeUleb128(OS, Rel.Type, "reloc type");
     writeUleb128(OS, Rel.Offset + Off, "reloc offset");
     writeUleb128(OS, File->calcNewIndex(Rel), "reloc index");
 
     switch (Rel.Type) {
     case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
     case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
     case R_WEBASSEMBLY_MEMORY_ADDR_I32:
-      writeUleb128(OS, Rel.Addend, "reloc addend");
+      writeSleb128(OS, Rel.Addend, "reloc addend");
       break;
     }
   }
 }
 
 void InputFunction::setFunctionIndex(uint32_t Index) {
   DEBUG(dbgs() << "InputFunction::setFunctionIndex: " << getName() << " -> "
                << Index << "\n");