[llvm] [CodeGen][ARM64EC] Use function symbol type for function alias symbols. (PR #92099)

[Jacek Caban via llvm-commits]

https://github.com/cjacek created https://github.com/llvm/llvm-project/pull/92099

Depends on #92098. I noticed that that's what MSVC does and it seems reasonable.

>From d5e57c33dbeb7a63ddf1c366db0153ceddf65780 Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek at codeweavers.com>
Date: Sat, 11 May 2024 16:41:24 +0200
Subject: [PATCH 1/2] [CodeGen][ARM64EC][NFC] Factor out emitFunctionAlias and
 getSymbolFromMetadata in emitFunctionEntryLabel.

---
 llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp | 71 +++++++++----------
 1 file changed, 32 insertions(+), 39 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp b/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
index ee39c6355c298..3ce766fc173c8 100644
--- a/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
+++ b/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
@@ -1161,52 +1161,45 @@ void AArch64AsmPrinter::emitFunctionEntryLabel() {
     TS->emitDirectiveVariantPCS(CurrentFnSym);
   }
 
+  AsmPrinter::emitFunctionEntryLabel();
+
   if (TM.getTargetTriple().isWindowsArm64EC() &&
       !MF->getFunction().hasLocalLinkage()) {
     // For ARM64EC targets, a function definition's name is mangled differently
-    // from the normal symbol. We emit the alias from the unmangled symbol to
-    // mangled symbol name here.
-    if (MDNode *Unmangled =
-            MF->getFunction().getMetadata("arm64ec_unmangled_name")) {
-      AsmPrinter::emitFunctionEntryLabel();
-
-      if (MDNode *ECMangled =
-              MF->getFunction().getMetadata("arm64ec_ecmangled_name")) {
-        StringRef UnmangledStr =
-            cast<MDString>(Unmangled->getOperand(0))->getString();
-        MCSymbol *UnmangledSym =
-            MMI->getContext().getOrCreateSymbol(UnmangledStr);
-        StringRef ECMangledStr =
-            cast<MDString>(ECMangled->getOperand(0))->getString();
-        MCSymbol *ECMangledSym =
-            MMI->getContext().getOrCreateSymbol(ECMangledStr);
-        OutStreamer->emitSymbolAttribute(UnmangledSym, MCSA_WeakAntiDep);
-        OutStreamer->emitAssignment(
-            UnmangledSym,
-            MCSymbolRefExpr::create(ECMangledSym, MCSymbolRefExpr::VK_WEAKREF,
-                                    MMI->getContext()));
-        OutStreamer->emitSymbolAttribute(ECMangledSym, MCSA_WeakAntiDep);
-        OutStreamer->emitAssignment(
-            ECMangledSym,
-            MCSymbolRefExpr::create(CurrentFnSym, MCSymbolRefExpr::VK_WEAKREF,
-                                    MMI->getContext()));
-        return;
+    // from the normal symbol, emit required aliases here.
+    auto emitFunctionAlias = [&](MCSymbol *Src, MCSymbol *Dst) {
+      OutStreamer->emitSymbolAttribute(Src, MCSA_WeakAntiDep);
+      OutStreamer->emitAssignment(
+          Src, MCSymbolRefExpr::create(Dst, MCSymbolRefExpr::VK_WEAKREF,
+                                       MMI->getContext()));
+    };
+
+    auto getSymbolFromMetadata = [&](StringRef Name) {
+      MCSymbol *Sym = nullptr;
+      if (MDNode *Node = MF->getFunction().getMetadata(Name)) {
+        StringRef NameStr = cast<MDString>(Node->getOperand(0))->getString();
+        Sym = MMI->getContext().getOrCreateSymbol(NameStr);
+      }
+      return Sym;
+    };
+
+    if (MCSymbol *UnmangledSym =
+            getSymbolFromMetadata("arm64ec_unmangled_name")) {
+      MCSymbol *ECMangledSym = getSymbolFromMetadata("arm64ec_ecmangled_name");
+
+      if (ECMangledSym) {
+        // An external function, emit the alias from the unmangled symbol to
+        // mangled symbol name and the alias from the mangled symbol to guest
+        // exit thunk.
+        emitFunctionAlias(UnmangledSym, ECMangledSym);
+        emitFunctionAlias(ECMangledSym, CurrentFnSym);
       } else {
-        StringRef UnmangledStr =
-            cast<MDString>(Unmangled->getOperand(0))->getString();
-        MCSymbol *UnmangledSym =
-            MMI->getContext().getOrCreateSymbol(UnmangledStr);
-        OutStreamer->emitSymbolAttribute(UnmangledSym, MCSA_WeakAntiDep);
-        OutStreamer->emitAssignment(
-            UnmangledSym,
-            MCSymbolRefExpr::create(CurrentFnSym, MCSymbolRefExpr::VK_WEAKREF,
-                                    MMI->getContext()));
-        return;
+        // A function implementation, emit the alias from the unmangled symbol
+        // to mangled symbol name.
+        emitFunctionAlias(UnmangledSym, CurrentFnSym);
       }
     }
   }
-
-  return AsmPrinter::emitFunctionEntryLabel();
 }
 
 /// Small jump tables contain an unsigned byte or half, representing the offset

>From f2f338716cd5be2d484f3854736a816c1c2da53d Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek at codeweavers.com>
Date: Sat, 11 May 2024 17:22:47 +0200
Subject: [PATCH 2/2] [CodeGen][ARM64EC] Use function symbol type for function
 alias symbols.

---
 llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp |  4 +++
 llvm/test/CodeGen/AArch64/arm64ec-symbols.ll  | 25 +++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 llvm/test/CodeGen/AArch64/arm64ec-symbols.ll

diff --git a/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp b/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
index 3ce766fc173c8..038ac14cd2898 100644
--- a/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
+++ b/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
@@ -1168,6 +1168,10 @@ void AArch64AsmPrinter::emitFunctionEntryLabel() {
     // For ARM64EC targets, a function definition's name is mangled differently
     // from the normal symbol, emit required aliases here.
     auto emitFunctionAlias = [&](MCSymbol *Src, MCSymbol *Dst) {
+      OutStreamer->beginCOFFSymbolDef(Src);
+      OutStreamer->emitCOFFSymbolType(COFF::IMAGE_SYM_DTYPE_FUNCTION
+                                      << COFF::SCT_COMPLEX_TYPE_SHIFT);
+      OutStreamer->endCOFFSymbolDef();
       OutStreamer->emitSymbolAttribute(Src, MCSA_WeakAntiDep);
       OutStreamer->emitAssignment(
           Src, MCSymbolRefExpr::create(Dst, MCSymbolRefExpr::VK_WEAKREF,
diff --git a/llvm/test/CodeGen/AArch64/arm64ec-symbols.ll b/llvm/test/CodeGen/AArch64/arm64ec-symbols.ll
new file mode 100644
index 0000000000000..9affdff0bacdc
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/arm64ec-symbols.ll
@@ -0,0 +1,25 @@
+; RUN: llc -mtriple=arm64ec-pc-windows-msvc < %s | FileCheck %s
+
+declare void @func() nounwind;
+
+define void @caller() nounwind {
+  call void @func()
+  ret void
+}
+
+; CHECK:      .def    caller;
+; CHECK-NEXT: .type   32;
+; CHECK-NEXT: .endef
+; CHECK-NEXT: .weak_anti_dep  caller
+; CHECK-NEXT: .set caller, "#caller"@WEAKREF
+
+; CHECK:      .def    func;
+; CHECK-NEXT: .type   32;
+; CHECK-NEXT: .endef
+; CHECK-NEXT: .weak_anti_dep  func
+; CHECK-NEXT: .set func, "#func"@WEAKREF
+; CHECK-NEXT: .def    "#func";
+; CHECK-NEXT: .type   32;
+; CHECK-NEXT: .endef
+; CHECK-NEXT: .weak_anti_dep  "#func"
+; CHECK-NEXT: .set "#func", "#func$exit_thunk"@WEAKREF