[llvm] [IR] Use EXPORTAS for ARM64EC mangled symbols with dllexport attribute. (PR #81940)

[Jacek Caban via llvm-commits]

https://github.com/cjacek updated https://github.com/llvm/llvm-project/pull/81940

>From c7a34699625cc4ab7209bc3999dde98b1a77ea31 Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek at codeweavers.com>
Date: Mon, 5 Feb 2024 22:04:23 +0100
Subject: [PATCH] [IR] Use EXPORTAS for ARM64EC mangled symbols with dllexport
 attribute.

---
 llvm/lib/IR/Mangler.cpp                | 14 ++++++++-
 llvm/test/CodeGen/AArch64/dllexport.ll | 39 ++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/IR/Mangler.cpp b/llvm/lib/IR/Mangler.cpp
index 3acac2c3e3db16..c4e8f005d6c8a9 100644
--- a/llvm/lib/IR/Mangler.cpp
+++ b/llvm/lib/IR/Mangler.cpp
@@ -18,8 +18,10 @@
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Module.h"
+#include "llvm/Object/COFF.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TargetParser/Triple.h"
+
 using namespace llvm;
 
 namespace {
@@ -192,7 +194,7 @@ void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
 
 // Check if the name needs quotes to be safe for the linker to interpret.
 static bool canBeUnquotedInDirective(char C) {
-  return isAlnum(C) || C == '_' || C == '@';
+  return isAlnum(C) || C == '_' || C == '@' || C == '#';
 }
 
 static bool canBeUnquotedInDirective(StringRef Name) {
@@ -233,6 +235,16 @@ void llvm::emitLinkerFlagsForGlobalCOFF(raw_ostream &OS, const GlobalValue *GV,
     } else {
       Mangler.getNameWithPrefix(OS, GV, false);
     }
+    if (TT.isWindowsArm64EC()) {
+      // Use EXPORTAS for mangled ARM64EC symbols.
+      // FIXME: During LTO, we're invoked prior to the EC lowering pass,
+      // so symbols are not yet mangled. Emitting the unmangled name
+      // typically functions correctly; the linker can resolve the export
+      // with the demangled alias.
+      if (std::optional<std::string> demangledName =
+              object::getArm64ECDemangledFunctionName(GV->getName()))
+        OS << ",EXPORTAS," << *demangledName;
+    }
     if (NeedQuotes)
       OS << "\"";
 
diff --git a/llvm/test/CodeGen/AArch64/dllexport.ll b/llvm/test/CodeGen/AArch64/dllexport.ll
index 81ba674a0dedc1..580fb5fd9e79ee 100644
--- a/llvm/test/CodeGen/AArch64/dllexport.ll
+++ b/llvm/test/CodeGen/AArch64/dllexport.ll
@@ -1,5 +1,7 @@
 ; RUN: llc -mtriple aarch64-windows-gnu -filetype asm -o - %s | FileCheck %s -check-prefix CHECK -check-prefix CHECK-GNU
 ; RUN: llc -mtriple aarch64-windows-msvc -filetype asm -o - %s | FileCheck %s -check-prefix CHECK -check-prefix CHECK-MSVC
+; RUN: llc -mtriple arm64ec-windows-gnu -filetype asm -o - %s | FileCheck %s -check-prefix CHECK -check-prefix CHECK-GNU-EC
+; RUN: llc -mtriple arm64ec-windows-msvc -filetype asm -o - %s | FileCheck %s -check-prefix CHECK -check-prefix CHECK-MSVC-EC
 
 define void @f() {
   ret void
@@ -71,3 +73,40 @@ define weak_odr dllexport void @l() {
 ; CHECK-MSVC: .ascii "  /EXPORT:s"
 ; CHECK-MSVC: .ascii "  /EXPORT:t"
 ; CHECK-MSVC: .ascii "  /EXPORT:u"
+
+; CHECK-GNU-EC-NOT: -export:f
+; CHECK-GNU-EC-NOT: -export:#f,EXPORTAS,f
+; CHECK-GNU-EC: .ascii " -export:#g,EXPORTAS,g
+; CHECK-GNU-EC: .ascii " -export:#h,EXPORTAS,h
+; CHECK-GNU-EC-NOT: -export:i
+; CHECK-GNU-EC-NOT: -export:#i,EXPORTAS,i
+; CHECK-GNU-EC: .ascii " -export:#j,EXPORTAS,j"
+; CHECK-GNU-EC: .ascii " -export:#k,EXPORTAS,k"
+; CHECK-GNU-EC: .ascii " -export:#l,EXPORTAS,l"
+; CHECK-GNU-EC: .ascii " -export:m,data"
+; CHECK-GNU-EC: .ascii " -export:n,data"
+; CHECK-GNU-EC: .ascii " -export:o,data"
+; CHECK-GNU-EC: .ascii " -export:p,data"
+; CHECK-GNU-EC: .ascii " -export:q,data"
+; CHECK-GNU-EC: .ascii " -export:r"
+; CHECK-GNU-EC: .ascii " -export:s"
+; CHECK-GNU-EC: .ascii " -export:t"
+; CHECK-GNU-EC: .ascii " -export:u"
+; CHECK-MSVC-EC-NOT: /EXPORT:f
+; CHECK-MSVC-EC-NOT: /EXPORT:#f,EXPORTAS,f
+; CHECK-MSVC-EC: .ascii "  /EXPORT:#g,EXPORTAS,g"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:#h,EXPORTAS,h"
+; CHECK-MSVC-EC-NOT: /EXPORT:i
+; CHECK-MSVC-EC-NOT: /EXPORT:#i,EXPORTAS,i
+; CHECK-MSVC-EC: .ascii "  /EXPORT:#j,EXPORTAS,j"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:#k,EXPORTAS,k"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:#l,EXPORTAS,l"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:m,DATA"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:n,DATA"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:o,DATA"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:p,DATA"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:q,DATA"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:r"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:s"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:t"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:u"