[lld] [lld][WebAssembly] Fix check for implicitly exported mutable globals (PR #160966)

[Sam Clegg via llvm-commits]

https://github.com/sbc100 created https://github.com/llvm/llvm-project/pull/160966

This change is designed to avoid exporting mutable globals in the case when mutable globals are not available.  However, it was being applied in all cases even when mutable globals was enabled.

>From 8687bf1a7be368830f1239a8e3fc09dccebe3773 Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc at chromium.org>
Date: Fri, 26 Sep 2025 16:05:44 -0700
Subject: [PATCH] [lld][WebAssembly] Fix check for implicitly exported mutable
 globals

This change is designed to avoid exporting mutable globals in the case
when mutable globals are not available.  However, it was being applied
in all cases even when mutable globals was enabled.
---
 lld/test/wasm/mutable-global-exports.s | 3 +++
 lld/wasm/Writer.cpp                    | 6 +++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/lld/test/wasm/mutable-global-exports.s b/lld/test/wasm/mutable-global-exports.s
index 4ffaf0a6cbaf0..1c10e92083b5c 100644
--- a/lld/test/wasm/mutable-global-exports.s
+++ b/lld/test/wasm/mutable-global-exports.s
@@ -73,6 +73,9 @@ _start:
 # CHECK-ALL-NEXT:      - Name:            __wasm_call_ctors
 # CHECK-ALL-NEXT:        Kind:            FUNCTION
 # CHECK-ALL-NEXT:        Index:           0
+# CHECK-ALL-NEXT:      - Name:            __stack_pointer
+# CHECK-ALL-NEXT:        Kind:            GLOBAL
+# CHECK-ALL-NEXT:        Index:           0
 # CHECK-ALL-NEXT:      - Name:            _start
 # CHECK-ALL-NEXT:        Kind:            FUNCTION
 # CHECK-ALL-NEXT:        Index:           1
diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
index 0d36893653110..9a5b56fc52e2f 100644
--- a/lld/wasm/Writer.cpp
+++ b/lld/wasm/Writer.cpp
@@ -784,6 +784,9 @@ void Writer::calculateExports() {
   unsigned globalIndex =
       out.importSec->getNumImportedGlobals() + out.globalSec->numGlobals();
 
+  bool hasMutableGlobals =
+      out.targetFeaturesSec->features.count("mutable-globals") > 0;
+
   for (Symbol *sym : symtab->symbols()) {
     if (!sym->isExported())
       continue;
@@ -801,7 +804,8 @@ void Writer::calculateExports() {
       }
       export_ = {name, WASM_EXTERNAL_FUNCTION, f->getExportedFunctionIndex()};
     } else if (auto *g = dyn_cast<DefinedGlobal>(sym)) {
-      if (g->getGlobalType()->Mutable && !g->getFile() && !g->forceExport) {
+      if (!hasMutableGlobals && g->getGlobalType()->Mutable && !g->getFile() &&
+          !g->isExportedExplicit()) {
         // Avoid exporting mutable globals are linker synthesized (e.g.
         // __stack_pointer or __tls_base) unless they are explicitly exported
         // from the command line.