Subzero: Refactor some common TargetLowering initializations.

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 87 matching lines @@
 TargetLowering *TargetLowering::createLowering(TargetArch Target, Cfg *Func) {
 #define SUBZERO_TARGET(X)                                                      \
   if (Target == Target_##X)                                                    \
     return Target##X::create(Func);
 #include "llvm/Config/SZTargets.def"
 
   Func->setError("Unsupported target");
   return nullptr;
 }
 
+void TargetLowering::staticInit(TargetArch Target) {
+  // Call the specified target's static initializer.
+  switch (Target) {
+  default:
+    llvm::report_fatal_error("Unsupported target");
+    break;
+#define SUBZERO_TARGET(X)                                                      \
+  case Target_##X: {                                                           \
+    static bool InitGuard##X = false;                                          \
+    if (InitGuard##X)                                                          \
+      return;                                                                  \
+    InitGuard##X = true;                                                       \
+    Target##X::staticInit();                                                   \
+  } break;
+#include "llvm/Config/SZTargets.def"
+  }
+}
+
 TargetLowering::TargetLowering(Cfg *Func)
     : Func(Func), Ctx(Func->getContext()), Context() {}
 
 std::unique_ptr<Assembler> TargetLowering::createAssembler(TargetArch Target,
                                                            Cfg *Func) {
 #define SUBZERO_TARGET(X)                                                      \
   if (Target == Target_##X)                                                    \
     return std::unique_ptr<Assembler>(new X::Assembler##X());
 #include "llvm/Config/SZTargets.def"
 
@@ skipping 507 matching lines @@
   if (Target == Target_##X)                                                    \
     return TargetHeader##X::create(Ctx);
 #include "llvm/Config/SZTargets.def"
 
   llvm::report_fatal_error("Unsupported target header lowering");
 }
 
 TargetHeaderLowering::~TargetHeaderLowering() = default;
 
 } // end of namespace Ice