[Cygwin] Emit COMDAT name correctly for Cygwin

Cygwin-gcc emits COMDAT in the same format as MinGW-gcc.

Author: kikairoya

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -1830,7 +1830,7 @@ MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
       // Append "$symbol" to the section name *before* IR-level mangling is
       // applied when targetting mingw. This is what GCC does, and the ld.bfd
       // COFF linker will not properly handle comdats otherwise.
-      if (getContext().getTargetTriple().isWindowsGNUEnvironment())
+      if (getContext().getTargetTriple().isOSCygMing())
         raw_svector_ostream(Name) << '$' << ComdatGV->getName();
 
       return getContext().getCOFFSection(Name, Characteristics, COMDATSymName,

llvm/test/CodeGen/X86/mingw-comdats-xdata.ll

@@ -1,5 +1,7 @@
 ; RUN: llc -mtriple=x86_64-w64-windows-gnu < %s | FileCheck %s --check-prefix=GNU
+; RUN: llc -mtriple=x86_64-pc-cygwin < %s | FileCheck %s --check-prefix=GNU
 ; RUN: llc -mtriple=x86_64-w64-windows-gnu < %s -filetype=obj | llvm-objdump - --headers | FileCheck %s --check-prefix=GNUOBJ
+; RUN: llc -mtriple=x86_64-pc-cygwin < %s -filetype=obj | llvm-objdump - --headers | FileCheck %s --check-prefix=GNUOBJ
 
 ; When doing GCC style comdats for MinGW, the .xdata sections don't have a normal comdat
 ; symbol attached, which requires a bit of adjustments for the assembler output.

llvm/test/CodeGen/X86/mingw-comdats.ll

@@ -1,8 +1,10 @@
 ; RUN: llc -function-sections -mtriple=x86_64-windows-itanium < %s | FileCheck %s
 ; RUN: llc -function-sections -mtriple=x86_64-windows-msvc < %s | FileCheck %s
 ; RUN: llc -function-sections -mtriple=x86_64-w64-windows-gnu < %s | FileCheck %s --check-prefix=GNU
+; RUN: llc -function-sections -mtriple=x86_64-pc-cygwin < %s | FileCheck %s --check-prefix=GNU
 ; RUN: llc -function-sections -mtriple=i686-w64-windows-gnu < %s | FileCheck %s --check-prefix=GNU32
 ; RUN: llc -function-sections -mtriple=x86_64-w64-windows-gnu < %s -filetype=obj | llvm-objdump - --headers | FileCheck %s --check-prefix=GNUOBJ
+; RUN: llc -function-sections -mtriple=x86_64-pc-cygwin < %s -filetype=obj | llvm-objdump - --headers | FileCheck %s --check-prefix=GNUOBJ
 
 ; GCC and MSVC handle comdats completely differently. Make sure we do the right
 ; thing for each.