[WebAssembly] Fixed LLD generation of 64-bit __wasm_init_memory

lld/test/wasm/data-segments.ll

 ; PASSIVE-PIC-NEXT:        Locals:          []
 ; PASSIVE-PIC-NEXT:        Body:            0B
 ; PASSIVE-PIC-NEXT:      - Index:           2
 ; PASSIVE-PIC-NEXT:        Locals:
 ; PASSIVE32-PIC-NEXT:          - Type:            I32
 ; PASSIVE64-PIC-NEXT:          - Type:            I64
 ; PASSIVE-PIC-NEXT:            Count:           1
 ; PASSIVE32-PIC-NEXT:        Body:            230141B4CE006A2100200041004101FE480200044020004101427FFE0102001A05410023016A4100410DFC080000411023016A41004114FC08010020004102FE1702002000417FFE0002001A0BFC0900FC09010B
-; PASSIVE64-PIC-NEXT:        Body:            230142B4CE006A2100200041004101FE480200044020004101427FFE0102001A05420023016A4100410DFC080000421023016A41004114FC08010020004102FE1702002000417FFE0002001A0BFC0900FC09010B
+; PASSIVE64-PIC-NEXT:        Body:            230142B4CE007C2100200041004101FE480200044020004101427FFE0102001A05420023017C4100410DFC080000421023017C41004114FC08010020004102FE1702002000417FFE0002001A0BFC0900FC09010B
 ; PASSIVE-PIC-NEXT:      - Index:           3
 ; PASSIVE-PIC-NEXT:        Locals:          []
 ; PASSIVE-PIC-NEXT:        Body:            0B
 ; PASSIVE-PIC-NEXT:  - Type:            DATA
 ; PASSIVE-PIC-NEXT:    Segments:
 ; PASSIVE-PIC-NEXT:      - SectionOffset:   3
 ; PASSIVE-PIC-NEXT:        InitFlags:       1
 ; PASSIVE-PIC-NEXT:        Content:         636F6E7374616E74000000002B

lld/wasm/Writer.cpp

std::string bodyContent;
     // With PIC code we cache the flag address in local 0
     if (config->isPic) {
       writeUleb128(os, 1, "num local decls");
       writeUleb128(os, 1, "local count");
       writeU8(os, is64 ? WASM_TYPE_I64 : WASM_TYPE_I32, "address type");
       writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET");
       writeUleb128(os, WasmSym::memoryBase->getGlobalIndex(), "memory_base");
       writePtrConst(os, flagAddress, is64, "flag address");
-      writeU8(os, WASM_OPCODE_I32_ADD, "add");
+      writeU8(os, is64 ? WASM_OPCODE_I64_ADD : WASM_OPCODE_I32_ADD, "add");
       writeU8(os, WASM_OPCODE_LOCAL_SET, "local.set");
       writeUleb128(os, 0, "local 0");
     } else {
       writeUleb128(os, 0, "num locals");
     }
 
     auto writeGetFlagAddress = [&]() {
       if (config->isPic) {
std::string bodyContent;
     for (const OutputSegment *s : segments) {
       if (needsPassiveInitialization(s)) {
         // destination address
         writePtrConst(os, s->startVA, is64, "destination address");
         if (config->isPic) {
           writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET");
           writeUleb128(os, WasmSym::memoryBase->getGlobalIndex(),
                        "memory_base");
-          writeU8(os, WASM_OPCODE_I32_ADD, "i32.add");
+          writeU8(os, is64 ? WASM_OPCODE_I64_ADD : WASM_OPCODE_I32_ADD,
+                  "i32.add");
         }
         // source segment offset
         writeI32Const(os, 0, "segment offset");
         // memory region size
         writeI32Const(os, s->size, "memory region size");
         // memory.init instruction
         writeU8(os, WASM_OPCODE_MISC_PREFIX, "bulk-memory prefix");
         writeUleb128(os, WASM_OPCODE_MEMORY_INIT, "memory.init");