[LLD][COFF] Add support for MinGW auto-export on ARM64X (llvm#125862)

Export all symbols from both EC and native symbol tables. If an explicit
export is present in either symbol table, auto-export is disabled for
both.

Author: cjacek

lld/COFF/Driver.cpp

@@ -1388,43 +1388,46 @@ void LinkerDriver::maybeExportMinGWSymbols(const opt::InputArgList &args) {
     if (!ctx.config.dll)
       return;
 
-    if (!ctx.symtab.exports.empty())
+    if (ctx.symtab.hadExplicitExports ||
+        (ctx.hybridSymtab && ctx.hybridSymtab->hadExplicitExports))
       return;
     if (args.hasArg(OPT_exclude_all_symbols))
       return;
   }
 
-  AutoExporter exporter(ctx, excludedSymbols);
+  ctx.forEachSymtab([&](SymbolTable &symtab) {
+    AutoExporter exporter(symtab, excludedSymbols);
 
-  for (auto *arg : args.filtered(OPT_wholearchive_file))
-    if (std::optional<StringRef> path = findFile(arg->getValue()))
-      exporter.addWholeArchive(*path);
+    for (auto *arg : args.filtered(OPT_wholearchive_file))
+      if (std::optional<StringRef> path = findFile(arg->getValue()))
+        exporter.addWholeArchive(*path);
 
-  for (auto *arg : args.filtered(OPT_exclude_symbols)) {
-    SmallVector<StringRef, 2> vec;
-    StringRef(arg->getValue()).split(vec, ',');
-    for (StringRef sym : vec)
-      exporter.addExcludedSymbol(ctx.symtab.mangle(sym));
-  }
+    for (auto *arg : args.filtered(OPT_exclude_symbols)) {
+      SmallVector<StringRef, 2> vec;
+      StringRef(arg->getValue()).split(vec, ',');
+      for (StringRef sym : vec)
+        exporter.addExcludedSymbol(symtab.mangle(sym));
+    }
 
-  ctx.symtab.forEachSymbol([&](Symbol *s) {
-    auto *def = dyn_cast<Defined>(s);
-    if (!exporter.shouldExport(def))
-      return;
+    symtab.forEachSymbol([&](Symbol *s) {
+      auto *def = dyn_cast<Defined>(s);
+      if (!exporter.shouldExport(def))
+        return;
 
-    if (!def->isGCRoot) {
-      def->isGCRoot = true;
-      ctx.config.gcroot.push_back(def);
-    }
+      if (!def->isGCRoot) {
+        def->isGCRoot = true;
+        ctx.config.gcroot.push_back(def);
+      }
 
-    Export e;
-    e.name = def->getName();
-    e.sym = def;
-    if (Chunk *c = def->getChunk())
-      if (!(c->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE))
-        e.data = true;
-    s->isUsedInRegularObj = true;
-    ctx.symtab.exports.push_back(e);
+      Export e;
+      e.name = def->getName();
+      e.sym = def;
+      if (Chunk *c = def->getChunk())
+        if (!(c->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE))
+          e.data = true;
+      s->isUsedInRegularObj = true;
+      symtab.exports.push_back(e);
+    });
   });
 }
 

lld/COFF/MinGW.cpp

@@ -25,9 +25,8 @@ using namespace lld;
 using namespace lld::coff;
 
 AutoExporter::AutoExporter(
-    COFFLinkerContext &ctx,
-    const llvm::DenseSet<StringRef> &manualExcludeSymbols)
-    : manualExcludeSymbols(manualExcludeSymbols), ctx(ctx) {
+    SymbolTable &symtab, const llvm::DenseSet<StringRef> &manualExcludeSymbols)
+    : manualExcludeSymbols(manualExcludeSymbols), symtab(symtab) {
   excludeLibs = {
       "libgcc",
       "libgcc_s",
@@ -89,7 +88,7 @@ AutoExporter::AutoExporter(
       "_NULL_THUNK_DATA",
   };
 
-  if (ctx.config.machine == I386) {
+  if (symtab.machine == I386) {
     excludeSymbols = {
         "__NULL_IMPORT_DESCRIPTOR",
         "__pei386_runtime_relocator",
@@ -156,7 +155,7 @@ bool AutoExporter::shouldExport(Defined *sym) const {
       return false;
 
   // If a corresponding __imp_ symbol exists and is defined, don't export it.
-  if (ctx.symtab.find(("__imp_" + sym->getName()).str()))
+  if (symtab.find(("__imp_" + sym->getName()).str()))
     return false;
 
   // Check that file is non-null before dereferencing it, symbols not

lld/COFF/MinGW.h

@@ -25,7 +25,7 @@ class COFFLinkerContext;
 // symbols for MinGW.
 class AutoExporter {
 public:
-  AutoExporter(COFFLinkerContext &ctx,
+  AutoExporter(SymbolTable &symtab,
                const llvm::DenseSet<StringRef> &manualExcludeSymbols);
 
   void addWholeArchive(StringRef path);
@@ -42,7 +42,7 @@ class AutoExporter {
   bool shouldExport(Defined *sym) const;
 
 private:
-  COFFLinkerContext &ctx;
+  SymbolTable &symtab;
 };
 
 void writeDefFile(COFFLinkerContext &, StringRef name,

lld/test/COFF/arm64x-export-all.s

@@ -0,0 +1,93 @@
+// REQUIRES: aarch64
+
+// RUN: llvm-mc -filetype=obj -triple=aarch64-windows %s -o %t.arm64.obj
+// RUN: llvm-mc -filetype=obj -triple=arm64ec-windows %s -o %t.arm64ec.obj
+// RUN: llvm-mc -filetype=obj -triple=arm64ec-windows %S/Inputs/loadconfig-arm64ec.s -o %t-loadconfig-arm64ec.obj
+// RUN: llvm-mc -filetype=obj -triple=aarch64-windows %S/Inputs/loadconfig-arm64.s -o %t-loadconfig-arm64.obj
+
+// Check that all symbols are exported in both EC and native views.
+
+// RUN: lld-link -machine:arm64x -lldmingw -dll -noentry -out:%t.dll %t.arm64.obj %t.arm64ec.obj %t-loadconfig-arm64.obj %t-loadconfig-arm64ec.obj
+
+// RUN: llvm-readobj --coff-exports %t.dll | FileCheck --check-prefix=EXP %s
+// EXP:      Format: COFF-ARM64X
+// EXP-NEXT: Arch: aarch64
+// EXP-NEXT: AddressSize: 64bit
+// EXP-NEXT: Export {
+// EXP-NEXT:   Ordinal: 1
+// EXP-NEXT:   Name: _load_config_used
+// EXP-NEXT:   RVA:
+// EXP-NEXT: }
+// EXP-NEXT: Export {
+// EXP-NEXT:   Ordinal: 2
+// EXP-NEXT:   Name: sym
+// EXP-NEXT:   RVA: 0x2000
+// EXP-NEXT: }
+// EXP-NEXT: Export {
+// EXP-NEXT:   Ordinal: 3
+// EXP-NEXT:   Name: sym2
+// EXP-NEXT:   RVA: 0x2004
+// EXP-NEXT: }
+// EXP-NEXT: HybridObject {
+// EXP-NEXT:   Format: COFF-ARM64EC
+// EXP-NEXT:   Arch: aarch64
+// EXP-NEXT:   AddressSize: 64bit
+// EXP-NEXT:   Export {
+// EXP-NEXT:     Ordinal: 1
+// EXP-NEXT:     Name: __chpe_metadata
+// EXP-NEXT:     RVA:
+// EXP-NEXT:   }
+// EXP-NEXT:   Export {
+// EXP-NEXT:     Ordinal: 2
+// EXP-NEXT:     Name: __os_arm64x_dispatch_icall
+// EXP-NEXT:     RVA: 0x12B0
+// EXP-NEXT:   }
+// EXP-NEXT:   Export {
+// EXP-NEXT:     Ordinal: 3
+// EXP-NEXT:     Name: __os_arm64x_dispatch_ret
+// EXP-NEXT:     RVA:
+// EXP-NEXT:   }
+// EXP-NEXT:   Export {
+// EXP-NEXT:     Ordinal: 4
+// EXP-NEXT:     Name: _load_config_used
+// EXP-NEXT:     RVA:
+// EXP-NEXT:   }
+// EXP-NEXT:   Export {
+// EXP-NEXT:     Ordinal: 5
+// EXP-NEXT:     Name: sym
+// EXP-NEXT:     RVA: 0x2008
+// EXP-NEXT:   }
+// EXP-NEXT:   Export {
+// EXP-NEXT:     Ordinal: 6
+// EXP-NEXT:     Name: sym2
+// EXP-NEXT:     RVA: 0x200C
+// EXP-NEXT:   }
+// EXP-NEXT: }
+
+// Check that an explicit export in the EC view is respected, preventing symbols from being auto-exported in both EC and native views.
+
+// RUN: lld-link -machine:arm64x -lldmingw -dll -noentry -out:%t2.dll %t.arm64.obj %t.arm64ec.obj -export:sym \
+// RUN:          %t-loadconfig-arm64.obj %t-loadconfig-arm64ec.obj
+
+// RUN: llvm-readobj --coff-exports %t2.dll | FileCheck --check-prefix=EXP2 %s
+// EXP2:      Format: COFF-ARM64X
+// EXP2-NEXT: Arch: aarch64
+// EXP2-NEXT: AddressSize: 64bit
+// EXP2-NEXT: HybridObject {
+// EXP2-NEXT:   Format: COFF-ARM64EC
+// EXP2-NEXT:   Arch: aarch64
+// EXP2-NEXT:   AddressSize: 64bit
+// EXP2-NEXT:   Export {
+// EXP2-NEXT:     Ordinal: 1
+// EXP2-NEXT:     Name: sym
+// EXP2-NEXT:     RVA: 0x2008
+// EXP2-NEXT:   }
+// EXP2-NEXT: }
+
+        .data
+        .globl sym
+sym:
+        .word 0
+        .globl sym2
+sym2:
+        .word 0