[lld][WebAssembly] Fix for TLS + --relocatable

[sbc100]

Summary

When running in -r/--relocatable we output relocations but the
new TLS relocations type was missing from ObjFile::calcNewAddend
causing this combination of inputs/flags to crash the linker.

Also avoid creating tls variables in relocatable mode. These variables
are only needed when linking final executables.

Fixes: https://github.com/emscripten-core/emscripten/issues/12934
Fixes: PR48506

[tlively]

It would be good to add a description of the bug to the commit description.

[sbc100]

rebase

lld/test/wasm/tls-no-shared.s

 # Test that linking without shared memory causes __tls_base to be
-# interlized
+# internalized
 
 # RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
 
 .globaltype __tls_base, i32
 
 .globl get_tls1
 get_tls1:
   .functype get_tls1 () -> (i32)

lld/test/wasm/tls.s

.section  .custom_section.target_features,"",@
   .ascii  "atomics"
   .int8 43
   .int8 11
   .ascii  "bulk-memory"
 
 # RUN: wasm-ld -no-gc-sections --shared-memory --max-memory=131072 --no-entry -o %t.wasm %t.o
 # RUN: obj2yaml %t.wasm | FileCheck %s
 
-# RUN: wasm-ld -no-gc-sections --shared-memory --max-memory=131072 --no-merge-data-segments --no-entry -o %t.wasm %t.o
-# RUN: obj2yaml %t.wasm | FileCheck %s
+# RUN: wasm-ld -no-gc-sections --shared-memory --max-memory=131072 --no-merge-data-segments --no-entry -o %t2.wasm %t.o
+# RUN: obj2yaml %t2.wasm | FileCheck %s
 
 # CHECK:      - Type:            GLOBAL
 # CHECK-NEXT:   Globals:
 # CHECK-NEXT:     - Index:           0
 # CHECK-NEXT:       Type:            I32
 # CHECK-NEXT:       Mutable:         true
 # CHECK-NEXT:       InitExpr:
 # CHECK-NEXT:         Opcode:          I32_CONST

 
 # CHECK-NEXT:     - Index:           5
 # CHECK-NEXT:       Locals:          []
 # CHECK-NEXT:       Body:            2383808080000B
 
 # Expected body of tls_align:
 #   global.get 3
 #   end
+
+
+# Also verify TLS usage with --relocatable
+# RUN: wasm-ld --relocatable -o %t3.wasm %t.o
+# RUN: obj2yaml %t3.wasm | FileCheck %s --check-prefix=RELOC
+
+# RELOC:       - Type:            IMPORT
+# RELOC-NEXT:    Imports:
+# RELOC-NEXT:      - Module:          env
+# RELOC-NEXT:        Field:           __tls_base
+# RELOC-NEXT:        Kind:            GLOBAL
+# RELOC-NEXT:        GlobalType:      I32
+# RELOC-NEXT:        GlobalMutable:   true
+# RELOC-NEXT:      - Module:          env
+# RELOC-NEXT:        Field:           __tls_align
+# RELOC-NEXT:        Kind:            GLOBAL
+# RELOC-NEXT:        GlobalType:      I32
+# RELOC-NEXT:        GlobalMutable:   false
+
+# RELOC:         GlobalNames:
+# RELOC-NEXT:      - Index:           0
+# RELOC-NEXT:        Name:            __tls_base
+# RELOC-NEXT:      - Index:           1
+# RELOC-NEXT:        Name:            __tls_align
+# RELOC-NEXT:    DataSegmentNames:
+# RELOC-NEXT:      - Index:           0
+# RELOC-NEXT:        Name:            .tdata
+# RELOC-NEXT:      - Index:           1
+# RELOC-NEXT:        Name:            .bss.no_tls

lld/wasm/Driver.cpp

if (config->isPic) {
     WasmSym::memoryBase->markLive();
     WasmSym::tableBase->markLive();
   } else {
     // For non-PIC code
     WasmSym::stackPointer = createGlobalVariable("__stack_pointer", true);
     WasmSym::stackPointer->markLive();
   }
 
-  if (config->sharedMemory) {
+  if (config->sharedMemory && !config->relocatable) {
     WasmSym::tlsBase = createGlobalVariable("__tls_base", true);
     WasmSym::tlsSize = createGlobalVariable("__tls_size", false);
     WasmSym::tlsAlign = createGlobalVariable("__tls_align", false);
     WasmSym::initTLS = symtab->addSyntheticFunction(
         "__wasm_init_tls", WASM_SYMBOL_VISIBILITY_HIDDEN,
         make<SyntheticFunction>(
             config->is64.getValueOr(false) ? i64ArgSignature : i32ArgSignature,
             "__wasm_init_tls"));

lld/wasm/InputFiles.cpp

uint64_t ObjFile::calcNewAddend(const WasmRelocation &reloc) const {
   case R_WASM_MEMORY_ADDR_LEB:
   case R_WASM_MEMORY_ADDR_LEB64:
   case R_WASM_MEMORY_ADDR_SLEB64:
   case R_WASM_MEMORY_ADDR_SLEB:
   case R_WASM_MEMORY_ADDR_REL_SLEB:
   case R_WASM_MEMORY_ADDR_REL_SLEB64:
   case R_WASM_MEMORY_ADDR_I32:
   case R_WASM_MEMORY_ADDR_I64:
+  case R_WASM_MEMORY_ADDR_TLS_SLEB:
   case R_WASM_FUNCTION_OFFSET_I32:
   case R_WASM_FUNCTION_OFFSET_I64:
     return reloc.Addend;
   case R_WASM_SECTION_OFFSET_I32:
     return getSectionSymbol(reloc.Index)->section->outputOffset + reloc.Addend;
   default:
     llvm_unreachable("unexpected relocation type");
   }

lld/wasm/Writer.cpp

void Writer::layoutMemory() {
   out.dylinkSec->memAlign = 0;
   for (OutputSegment *seg : segments) {
     out.dylinkSec->memAlign = std::max(out.dylinkSec->memAlign, seg->alignment);
     memoryPtr = alignTo(memoryPtr, 1ULL << seg->alignment);
     seg->startVA = memoryPtr;
     log(formatv("mem: {0,-15} offset={1,-8} size={2,-8} align={3}", seg->name,
                 memoryPtr, seg->size, seg->alignment));
 
-    if (seg->name == ".tdata") {
+    if (!config->relocatable && seg->name == ".tdata") {
       if (config->sharedMemory) {
         auto *tlsSize = cast<DefinedGlobal>(WasmSym::tlsSize);
         setGlobalPtr(tlsSize, seg->size);
 
         auto *tlsAlign = cast<DefinedGlobal>(WasmSym::tlsAlign);
         setGlobalPtr(tlsAlign, int64_t{1} << seg->alignment);
       } else {
         auto *tlsBase = cast<DefinedGlobal>(WasmSym::tlsBase);