[lld][WebAssembly] Use writePtrConst helper function (#166228)

This is especially important for writing i32 values larger than 2gb
which need to be encoded as negative SLEB vales in the binary.

Without this change offsets over 2gb are wrongly encoded and cause
validation errors.

Fixes: emscripten-core/emscripten#25706

Author: sbc100

lld/test/wasm/runtime-relocations-himem.s

@@ -0,0 +1,60 @@
+## Verifies runtime relocation code for addresses over 2gb works correctly.
+## We have had issues with LEB encoding of address over 2gb in i32.const
+## instruction leading to invalid binaries.
+
+# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
+# RUN: wasm-ld --global-base=2147483648 --experimental-pic --unresolved-symbols=import-dynamic -no-gc-sections --shared-memory --no-entry -o %t.wasm %t.o
+# XUN: obj2yaml %t.wasm | FileCheck %s
+# RUN: llvm-objdump -d --no-show-raw-insn --no-leading-addr %t.wasm | FileCheck %s --
+
+.globl tls_sym
+.globl data_sym
+.globl _start
+.globaltype __tls_base, i32
+
+_start:
+  .functype _start () -> ()
+  global.get __tls_base
+  i32.const tls_sym@TLSREL
+  i32.add
+  drop
+  i32.const data_sym
+  drop
+  end_function
+
+.section tls_sec,"T",@
+.p2align  2
+tls_sym:
+  .int32 0
+  .int32 extern_sym
+  .size tls_sym, 8
+
+.section data_sec,"",@
+.p2align  2
+data_sym:
+  .int32 0
+  .int32 extern_sym
+  .size data_sym, 8
+
+.section  .custom_section.target_features,"",@
+  .int8 2
+  .int8 43
+  .int8 7
+  .ascii  "atomics"
+  .int8 43
+  .int8 11
+  .ascii  "bulk-memory"
+
+# CHECK: <__wasm_apply_data_relocs>:
+# CHECK-EMPTY:
+# CHECK-NEXT:  i32.const -2147483636
+# CHECK-NEXT:  global.get 0
+# CHECK-NEXT:  i32.store 0
+# CHECK-NEXT:  end
+
+# CHECK: <__wasm_apply_tls_relocs>:
+# CHECK-EMPTY:
+# CHECK-NEXT:  i32.const -2147483644
+# CHECK-NEXT:  global.get 0
+# CHECK-NEXT:  i32.store 0
+# CHECK-NEXT:  end

lld/wasm/InputChunks.cpp

@@ -423,8 +423,6 @@ bool InputChunk::generateRelocationCode(raw_ostream &os) const {
 
   bool is64 = ctx.arg.is64.value_or(false);
   bool generated = false;
-  unsigned opcode_ptr_const = is64 ? WASM_OPCODE_I64_CONST
-                                   : WASM_OPCODE_I32_CONST;
   unsigned opcode_ptr_add = is64 ? WASM_OPCODE_I64_ADD
                                  : WASM_OPCODE_I32_ADD;
 
@@ -451,8 +449,7 @@ bool InputChunk::generateRelocationCode(raw_ostream &os) const {
                       << " output offset=" << offset << "\n");
 
     // Calculate the address at which to apply the relocation
-    writeU8(os, opcode_ptr_const, "CONST");
-    writeSleb128(os, offset, "offset");
+    writePtrConst(os, offset, is64, "offset");
 
     // In PIC mode we need to add the __memory_base
     if (ctx.isPic) {
@@ -466,8 +463,6 @@ bool InputChunk::generateRelocationCode(raw_ostream &os) const {
 
     // Now figure out what we want to store at this location
     bool is64 = relocIs64(rel.Type);
-    unsigned opcode_reloc_const =
-        is64 ? WASM_OPCODE_I64_CONST : WASM_OPCODE_I32_CONST;
     unsigned opcode_reloc_add =
         is64 ? WASM_OPCODE_I64_ADD : WASM_OPCODE_I32_ADD;
     unsigned opcode_reloc_store =
@@ -477,8 +472,7 @@ bool InputChunk::generateRelocationCode(raw_ostream &os) const {
       writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET");
       writeUleb128(os, sym->getGOTIndex(), "global index");
       if (rel.Addend) {
-        writeU8(os, opcode_reloc_const, "CONST");
-        writeSleb128(os, rel.Addend, "addend");
+        writePtrConst(os, rel.Addend, is64, "addend");
         writeU8(os, opcode_reloc_add, "ADD");
       }
     } else {
@@ -491,8 +485,8 @@ bool InputChunk::generateRelocationCode(raw_ostream &os) const {
         baseSymbol = ctx.sym.tlsBase;
       writeU8(os, WASM_OPCODE_GLOBAL_GET, "GLOBAL_GET");
       writeUleb128(os, baseSymbol->getGlobalIndex(), "base");
-      writeU8(os, opcode_reloc_const, "CONST");
-      writeSleb128(os, file->calcNewValue(rel, tombstone, this), "offset");
+      writePtrConst(os, file->calcNewValue(rel, tombstone, this), is64,
+                    "offset");
       writeU8(os, opcode_reloc_add, "ADD");
     }
 

lld/wasm/SyntheticSections.cpp

@@ -434,8 +434,6 @@ void GlobalSection::addInternalGOTEntry(Symbol *sym) {
 void GlobalSection::generateRelocationCode(raw_ostream &os, bool TLS) const {
   assert(!ctx.arg.extendedConst);
   bool is64 = ctx.arg.is64.value_or(false);
-  unsigned opcode_ptr_const = is64 ? WASM_OPCODE_I64_CONST
-                                   : WASM_OPCODE_I32_CONST;
   unsigned opcode_ptr_add = is64 ? WASM_OPCODE_I64_ADD
                                  : WASM_OPCODE_I32_ADD;
 
@@ -452,8 +450,7 @@ void GlobalSection::generateRelocationCode(raw_ostream &os, bool TLS) const {
         writeUleb128(os, ctx.sym.memoryBase->getGlobalIndex(), "__memory_base");
 
       // Add the virtual address of the data symbol
-      writeU8(os, opcode_ptr_const, "CONST");
-      writeSleb128(os, d->getVA(), "offset");
+      writePtrConst(os, d->getVA(), is64, "offset");
     } else if (auto *f = dyn_cast<FunctionSymbol>(sym)) {
       if (f->isStub)
         continue;
@@ -462,8 +459,7 @@ void GlobalSection::generateRelocationCode(raw_ostream &os, bool TLS) const {
       writeUleb128(os, ctx.sym.tableBase->getGlobalIndex(), "__table_base");
 
       // Add the table index to __table_base
-      writeU8(os, opcode_ptr_const, "CONST");
-      writeSleb128(os, f->getTableIndex(), "offset");
+      writePtrConst(os, f->getTableIndex(), is64, "offset");
     } else {
       assert(isa<UndefinedData>(sym) || isa<SharedData>(sym));
       continue;