[lld] [GHC] wasm-ld: split up __wasm_apply_data_relocs (PR #129007)

[Sam Clegg via llvm-commits]

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@@ -1485,24 +1486,67 @@ void Writer::createApplyDataRelocationsFunction() {
       make<SyntheticFunction>(nullSignature, "__wasm_apply_data_relocs"));
   def->markLive();
 
-  createFunction(def, bodyContent);
+  if (funcs.size() == 1) {
+    createFunction(def, funcs.back());
+    return;
+  }
+
+  std::string body;
+  {
+    raw_string_ostream os(body);
+    writeUleb128(os, 0, "num locals");
+
+    for (std::size_t i = 0; i < funcs.size(); ++i) {
+      auto &name =
+          *make<std::string>("__wasm_apply_data_relocs_" + std::to_string(i));
+      auto *func = make<SyntheticFunction>(nullSignature, name);
+      auto *def = symtab->addSyntheticFunction(
+          name, WASM_SYMBOL_VISIBILITY_HIDDEN, func);
+      def->markLive();
+      // Normally this shouldn't be called manually for a synthetic
+      // function, since the function indices in
+      // ctx.syntheticFunctions will be calculated later (check
+      // functionSec->addFunction call hierarchy for details).
+      // However, at this point we already need the correct index. The
+      // solution is to place the new synthetic function eagerly, and
+      // also making addFunction idempotent by skipping when there's
+      // already a function index.
----------------
sbc100 wrote:

I guess that alternative to this would be to somehow generate relocations here.

I wonder how this works for other synthetic functions that can call each such as `__wasm_init_memory`?

https://github.com/llvm/llvm-project/pull/129007