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

[Jacek Caban via llvm-commits]

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

We currently just use mangled name. This works fine, because linker should detect that and demangle it for the export table. However, on MSVC, the compiler is more specific and passes demangled name as well, with EXPORTAS. This PR aims to match that. MSVC doesn't use quotes in this case, so I added '#' to the list of characters that don't need it.

>From 7746a011b271f2b20b2503955692a7d7510d2b7e 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                |  9 +++++-
 llvm/test/CodeGen/AArch64/dllexport.ll | 39 ++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/IR/Mangler.cpp b/llvm/lib/IR/Mangler.cpp
index 3acac2c3e3db16..9d6a0ef6ec3aae 100644
--- a/llvm/lib/IR/Mangler.cpp
+++ b/llvm/lib/IR/Mangler.cpp
@@ -20,6 +20,8 @@
 #include "llvm/IR/Module.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TargetParser/Triple.h"
+#include "llvm/Object/COFF.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 +235,11 @@ void llvm::emitLinkerFlagsForGlobalCOFF(raw_ostream &OS, const GlobalValue *GV,
     } else {
       Mangler.getNameWithPrefix(OS, GV, false);
     }
+    if (TT.isWindowsArm64EC()) {
+      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..5f2628619dcc3d 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-NOT-EC: -export:f
+; CHECK-GNU-NOT-EC: -export:#f,EXPORTAS,f
+; CHECK-GNU-EC: .ascii " -export:#g,EXPORTAS,g
+; CHECK-GNU-EC: .ascii " -export:#h,EXPORTAS,h
+; CHECK-GNU-NOT-EC: -export:i
+; CHECK-GNU-NOT-EC: -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-NOT-EC: /EXPORT:f
+; CHECK-MSVC-NOT-EC: /EXPORT:#f,EXPORTAS,f
+; CHECK-MSVC-EC: .ascii "  /EXPORT:#g,EXPORTAS,g"
+; CHECK-MSVC-EC: .ascii "  /EXPORT:#h,EXPORTAS,h"
+; CHECK-MSVC-NOT-EC: /EXPORT:i
+; CHECK-MSVC-NOT-EC: /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"