[Cygwin] Enable TLS as emutls.

It resolves clang selfhosting with std::once() for Cygwin.

FIXME: It may be EmulatedTLS-generic also for X86-Android.
FIXME: Pass EmulatedTLS to LLVM CodeGen from Clang with -femulated-tls.
llvm-svn: 256134

clang/lib/Basic/Targets.cpp

@@ -3834,7 +3834,6 @@ class CygwinX86_32TargetInfo : public X86_32TargetInfo {
 public:
   CygwinX86_32TargetInfo(const llvm::Triple &Triple)
       : X86_32TargetInfo(Triple) {
-    TLSSupported = false;
     WCharType = UnsignedShort;
     DoubleAlign = LongLongAlign = 64;
     DataLayoutString = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32";

clang/test/CXX/concepts-ts/dcl.dcl/dcl.spec/dcl.spec.concept/p2.cpp

@@ -1,5 +1,4 @@
 // RUN:  %clang_cc1 -std=c++14 -fconcepts-ts -x c++ -verify %s
-// REQUIRES: tls
 
 template<typename T> concept thread_local bool VCTL = true; // expected-error {{variable concept cannot be declared 'thread_local'}}
 

clang/test/OpenMP/parallel_copyin_codegen.cpp

@@ -11,7 +11,6 @@
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -std=c++11 -DLAMBDA -triple %itanium_abi_triple -emit-llvm %s -o - | FileCheck -check-prefix=TLS-LAMBDA %s
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -fblocks -DBLOCKS -triple %itanium_abi_triple -emit-llvm %s -o - | FileCheck -check-prefix=TLS-BLOCKS %s
 // RUN: %clang_cc1 -verify -fopenmp -x c++ -std=c++11 -DARRAY -triple x86_64-linux-gnu -emit-llvm %s -o - | FileCheck -check-prefix=TLS-ARRAY %s
-// REQUIRES: tls
 // expected-no-diagnostics
 #ifndef ARRAY
 #ifndef HEADER

clang/test/PCH/chain-openmp-threadprivate.cpp

@@ -9,8 +9,6 @@
 // RUN: %clang_cc1 -fopenmp -emit-llvm -chain-include %s -chain-include %s %s -o - | FileCheck %s -check-prefix=CHECK-TLS-1
 // RUN: %clang_cc1 -fopenmp -emit-llvm -chain-include %s -chain-include %s %s -o - | FileCheck %s -check-prefix=CHECK-TLS-2
 
-// REQUIRES: tls
-
 #if !defined(PASS1)
 #define PASS1
 

llvm/docs/ReleaseNotes.rst

@@ -105,6 +105,14 @@ Changes to the PowerPC Target
  During this release ...
 
 
+Changes to the X86 Target
+-----------------------------
+
+ During this release ...
+
+* TLS is enabled for Cygwin as emutls.
+
+
 Changes to the OCaml bindings
 -----------------------------
 

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -12258,6 +12258,12 @@ SDValue
 X86TargetLowering::LowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const {
 
   GlobalAddressSDNode *GA = cast<GlobalAddressSDNode>(Op);
+
+  // Cygwin uses emutls.
+  // FIXME: It may be EmulatedTLS-generic also for X86-Android.
+  if (Subtarget->isTargetWindowsCygwin())
+    return LowerToTLSEmulatedModel(GA, DAG);
+
   const GlobalValue *GV = GA->getGlobal();
   auto PtrVT = getPointerTy(DAG.getDataLayout());