Subzero: Refactor some common TargetLowering initializations.

src/IceTargetLowering.cpp

Index: src/IceTargetLowering.cpp
diff --git a/src/IceTargetLowering.cpp b/src/IceTargetLowering.cpp
index 4902a3d64a8637a75decad7d1012ee626cd608a9..b4270f92832dbc691b58abee7d94a1fb7eb701fc 100644
--- a/src/IceTargetLowering.cpp
+++ b/src/IceTargetLowering.cpp
@@ -105,6 +105,25 @@ TargetLowering *TargetLowering::createLowering(TargetArch Target, Cfg *Func) {
   return nullptr;
 }
 
+void TargetLowering::staticInit(TargetArch Target) {
+  static bool InitGuard = false;

[John, 2015/11/04 21:35:23]

Not that this matter, but if in the future we allow multiple targets to be
loaded at the same time, this will prevent all but the first target to
initialize.

why not invoking staticInit() on everything, and letting SZTargets.def handle
things a bit?

[Jim Stichnoth, 2015/11/04 23:51:39]

I did something like that originally, by duplicating the init guard stuff across
all the target source files, decided I didn't like the duplication, and
refactored it here.

But you're right, that does unnecessarily constrain the number of active targets
during a run.

Done.

+  if (InitGuard)
+    return;
+  InitGuard = true;
+
+  // Call the specified target's static initializer.
+  switch (Target) {
+  default:
+    llvm::report_fatal_error("Unsupported target");
+    break;
+#define SUBZERO_TARGET(X)                                                      \
+  case Target_##X:                                                             \
+    Target##X::staticInit();                                                   \
+    break;
+#include "llvm/Config/SZTargets.def"
+  }
+}
+
 TargetLowering::TargetLowering(Cfg *Func)
     : Func(Func), Ctx(Func->getContext()), Context() {}