[llvm] [Cygwin] Fix global variable dll import (PR #121439)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: 王宇逸 (Berrysoft)

<details>
<summary>Changes</summary>

This PR is necessary for cygwin target of Rust.

References:
* https://github.com/rust-lang/llvm-project/commit/86657cc39f8e42ae73be810fb0703ddac0eeef94
* https://github.com/Berrysoft/llvm-project/commit/a807e9f077351d3c6a68f4abe74c94a039759a2e

---
Full diff: https://github.com/llvm/llvm-project/pull/121439.diff


2 Files Affected:

- (modified) llvm/lib/Target/TargetMachine.cpp (+1-1) 
- (modified) llvm/test/CodeGen/X86/mingw-refptr.ll (+1) 


``````````diff
diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index c0985f3be91a53..d5365f3c047437 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -204,7 +204,7 @@ bool TargetMachine::shouldAssumeDSOLocal(const GlobalValue *GV) const {
     // don't assume the variables to be DSO local unless we actually know
     // that for sure. This only has to be done for variables; for functions
     // the linker can insert thunks for calling functions from another DLL.
-    if (TT.isWindowsGNUEnvironment() && GV->isDeclarationForLinker() &&
+    if (TT.isOSCygMing() && GV->isDeclarationForLinker() &&
         isa<GlobalVariable>(GV))
       return false;
 
diff --git a/llvm/test/CodeGen/X86/mingw-refptr.ll b/llvm/test/CodeGen/X86/mingw-refptr.ll
index 73f1a9880913c9..82a90aba386546 100644
--- a/llvm/test/CodeGen/X86/mingw-refptr.ll
+++ b/llvm/test/CodeGen/X86/mingw-refptr.ll
@@ -1,4 +1,5 @@
 ; RUN: llc < %s -mtriple=x86_64-w64-mingw32 | FileCheck %s -check-prefix=CHECK-X64
+; RUN: llc < %s -mtriple=x86_64-pc-cygwin | FileCheck %s -check-prefix=CHECK-X64
 ; RUN: llc < %s -mtriple=i686-w64-mingw32 | FileCheck %s -check-prefix=CHECK-X86
 ; RUN: llc < %s -mtriple=i686-w64-mingw32-none-elf | FileCheck %s -check-prefix=CHECK-X86-ELF
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/121439