diff --git a/include/dxc/Support/Global.h b/include/dxc/Support/Global.h
index 47c68b028..b18cdf35d 100644
--- a/include/dxc/Support/Global.h
+++ b/include/dxc/Support/Global.h
@@ -60,8 +60,6 @@ IMalloc *DxcSwapThreadMallocOrDefault(IMalloc *pMalloc, IMalloc **ppPrior) throw
 
 // Used to retrieve the current invocation's allocator or perform an alloc/free/realloc.
 IMalloc *DxcGetThreadMallocNoRef() throw();
-_Ret_maybenull_ _Post_writable_byte_size_(nBytes) void *DxcThreadAlloc(size_t nBytes) throw();
-void DxcThreadFree(void *) throw();
 
 struct DxcThreadMalloc {
   DxcThreadMalloc(IMalloc *pMallocOrNull) throw() {
diff --git a/lib/DxcSupport/HLSLOptions.cpp b/lib/DxcSupport/HLSLOptions.cpp
index d1adbe16b..4d1943a5e 100644
--- a/lib/DxcSupport/HLSLOptions.cpp
+++ b/lib/DxcSupport/HLSLOptions.cpp
@@ -49,6 +49,10 @@ namespace {
 
 static HlslOptTable *g_HlslOptTable;
 
+#ifndef _WIN32
+#pragma GCC visibility push(hidden)
+#endif
+
 std::error_code hlsl::options::initHlslOptTable() {
   DXASSERT(g_HlslOptTable == nullptr, "else double-init");
   g_HlslOptTable = new (std::nothrow) HlslOptTable();
@@ -66,6 +70,10 @@ const OptTable * hlsl::options::getHlslOptTable() {
   return g_HlslOptTable;
 }
 
+#ifndef _WIN32
+#pragma GCC visibility pop
+#endif
+
 void DxcDefines::push_back(llvm::StringRef value) {
   // Skip empty defines.
   if (value.size() > 0) {
diff --git a/lib/DxcSupport/dxcmem.cpp b/lib/DxcSupport/dxcmem.cpp
index ae9331ab2..3bef28f06 100644
--- a/lib/DxcSupport/dxcmem.cpp
+++ b/lib/DxcSupport/dxcmem.cpp
@@ -21,19 +21,9 @@
 static llvm::sys::ThreadLocal<IMalloc> *g_ThreadMallocTls;
 static IMalloc *g_pDefaultMalloc;
 
-// Used by DllMain to set up and tear down per-thread tracking.
-HRESULT DxcInitThreadMalloc() throw();
-void DxcCleanupThreadMalloc() throw();
-
-// Used by APIs that are entry points to set up per-thread/invocation allocator.
-void DxcSetThreadMalloc(IMalloc *pMalloc) throw();
-void DxcSetThreadMallocOrDefault(IMalloc *pMalloc) throw(); 
-void DxcClearThreadMalloc() throw();
-
-// Used to retrieve the current invocation's allocator or perform an alloc/free/realloc.
-IMalloc *DxcGetThreadMallocNoRef() throw();
-_Ret_maybenull_ _Post_writable_byte_size_(nBytes) void *DxcThreadAlloc(size_t nBytes) throw();
-void DxcThreadFree(void *) throw();
+#ifndef _WIN32
+#pragma GCC visibility push(hidden)
+#endif
 
 HRESULT DxcInitThreadMalloc() throw() {
   DXASSERT(g_pDefaultMalloc == nullptr, "else InitThreadMalloc already called");
@@ -96,3 +86,7 @@ IMalloc *DxcSwapThreadMalloc(IMalloc *pMalloc, IMalloc **ppPrior) throw() {
 IMalloc *DxcSwapThreadMallocOrDefault(IMalloc *pMallocOrNull, IMalloc **ppPrior) throw() {
   return DxcSwapThreadMalloc(pMallocOrNull ? pMallocOrNull : g_pDefaultMalloc, ppPrior);
 }
+
+#ifndef _WIN32
+#pragma GCC visibility pop
+#endif
diff --git a/lib/Support/regerror.c b/lib/Support/regerror.c
index 9c7e0a6a0..95b3ae89c 100644
--- a/lib/Support/regerror.c
+++ b/lib/Support/regerror.c
@@ -108,12 +108,15 @@ llvm_regerror(int errcode, const llvm_regex_t *preg, _Out_writes_all_(errbuf_siz
 				assert(strlen(r->name) < sizeof(convbuf));
 				(void) llvm_strlcpy(convbuf, r->name, sizeof convbuf);
 			} else
+                          // Begin HLSL Change
 #ifdef _WIN32
 				(void)_snprintf_s(convbuf, _countof(convbuf), _countof(convbuf),
+				    "REG_0x%x", target);
 #else
 				(void)snprintf(convbuf, sizeof convbuf,
-#endif // WIN32
 				    "REG_0x%x", target);
+#endif // WIN32
+                          // End HLSL Change
 			s = convbuf;
 		} else
 			s = r->explain;
diff --git a/lib/Support/regex_impl.h b/lib/Support/regex_impl.h
index 4340bbf03..bbf64cfb2 100644
--- a/lib/Support/regex_impl.h
+++ b/lib/Support/regex_impl.h
@@ -35,8 +35,8 @@
  *	@(#)regex.h	8.1 (Berkeley) 6/2/93
  */
 
-#ifndef _REGEX_H_
-#define	_REGEX_H_
+#ifndef _REGEX_IMPL_H_ // HLSL Change
+#define _REGEX_IMPL_H_ // HLSL Change
 
 #include "dxc/Support/WinAdapter.h" // HLSL Change
 #include <sys/types.h>
@@ -119,4 +119,4 @@ size_t  llvm_strlcpy(
 }
 #endif
 
-#endif /* !_REGEX_H_ */
+#endif /* !_REGEX_IMPL_H_ */ // HLSL Change
diff --git a/tools/clang/tools/dxcompiler/DXCompiler.cpp b/tools/clang/tools/dxcompiler/DXCompiler.cpp
index 894f2ea6d..77a6a9fcf 100644
--- a/tools/clang/tools/dxcompiler/DXCompiler.cpp
+++ b/tools/clang/tools/dxcompiler/DXCompiler.cpp
@@ -14,7 +14,9 @@
 #include "dxc/Support/Global.h"
 #include "dxc/Support/WinIncludes.h"
 #include "dxc/Support/HLSLOptions.h"
+#ifdef LLVM_ON_WIN32
 #include "dxcetw.h"
+#endif
 #include "dxillib.h"
 
 namespace hlsl { HRESULT SetupRegistryPassForHLSL(); }
@@ -22,6 +24,7 @@ namespace hlsl { HRESULT SetupRegistryPassForHLSL(); }
 // C++ exception specification ignored except to indicate a function is not __declspec(nothrow)
 #pragma warning( disable : 4290 )
 
+#ifdef LLVM_ON_WIN32
 // operator new and friends.
 void *  __CRTDECL operator new(std::size_t size) throw(std::bad_alloc) {
   void * ptr = DxcGetThreadMallocNoRef()->Alloc(size);
@@ -39,6 +42,7 @@ void  __CRTDECL operator delete (void* ptr) throw() {
 void  __CRTDECL operator delete (void* ptr, const std::nothrow_t& nothrow_constant) throw() {
   DxcGetThreadMallocNoRef()->Free(ptr);
 }
+#endif
 
 static HRESULT InitMaybeFail() throw() {
   HRESULT hr;
@@ -72,7 +76,20 @@ Cleanup:
   }
   return hr;
 }
+#if defined(LLVM_ON_UNIX)
+HRESULT __attribute__ ((constructor)) DllMain() {
+  return InitMaybeFail();
+}
 
+void __attribute__ ((destructor)) DllShutdown() {
+  DxcSetThreadMallocOrDefault(nullptr);
+  ::hlsl::options::cleanupHlslOptTable();
+  ::llvm::sys::fs::CleanupPerThreadFileSystem();
+  ::llvm::llvm_shutdown();
+  DxcClearThreadMalloc();
+  DxcCleanupThreadMalloc();
+}
+#else // LLVM_ON_UNIX
 BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD Reason, LPVOID reserved) {
   BOOL result = TRUE;
   if (Reason == DLL_PROCESS_ATTACH) {
@@ -102,3 +119,4 @@ BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD Reason, LPVOID reserved) {
 
   return result;
 }
+#endif // LLVM_ON_UNIX