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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: Jacek Caban (cjacek)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/81940.diff


2 Files Affected:

- (modified) llvm/lib/IR/Mangler.cpp (+8-1) 
- (modified) llvm/test/CodeGen/AArch64/dllexport.ll (+39) 


``````````diff
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"

``````````

</details>


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