[CIR] Add support for thread-local storage (TLS) (#168662)
This commit adds full support for thread-local storage variables in
ClangIR, including code generation, lowering to LLVM IR, and
comprehensive testing.
Changes include:
- Added CIR_TLSModel enum with 4 TLS models (GeneralDynamic,
LocalDynamic, InitialExec, LocalExec) to CIROps.td
- Extended GlobalOp with optional tls_model attribute
- Extended GetGlobalOp with thread_local unit attribute
- Added verification to ensure thread_local GetGlobalOp references
globals with tls_model set
- Implemented GetDefaultCIRTLSModel() and setTLSMode() in CIRGenModule
- Updated getAddrOfGlobalVar() to handle TLS access
- Removed MissingFeatures assertions for TLS operations
- Added lowering of GetGlobalOp with TLS to llvm.threadlocal.address
intrinsic
- Added lowering of GlobalOp with tls_model to LLVM thread_local globals
- Added comprehensive test with CIR, LLVM, and OGCG checks
Known limitations (matching incubator):
- Static local TLS variables not yet implemented
- TLS_Dynamic with wrapper functions not yet implemented
Fixes #153270
