Remove unused variable in GC root placement

[ararslan]

This was causing an unused variable warning when building with Clang.

[yuyichao]

Looks like the requirement on DOM wrapper pass can be removed?

[Keno]

Yeah that too. Wouldn't be surprised if we started needing it again at some point, but let's get rid of it for now.

[ararslan]

To be honest I'm not really sure how to do that. This is my best guess, is it right?

diff --git a/src/llvm-late-gc-lowering.cpp b/src/llvm-late-gc-lowering.cpp
index 4a613febd8..f617c2f98a 100644
--- a/src/llvm-late-gc-lowering.cpp
+++ b/src/llvm-late-gc-lowering.cpp
@@ -6,7 +6,6 @@
 #include "llvm/Analysis/CFG.h"
 #include <llvm/IR/Value.h>
 #include <llvm/IR/Constants.h>
-#include <llvm/IR/Dominators.h>
 #include <llvm/IR/Function.h>
 #include <llvm/IR/Instructions.h>
 #include <llvm/IR/IntrinsicInst.h>
@@ -290,15 +289,12 @@ struct LateLowerGCFrame: public FunctionPass {
     static char ID;
     LateLowerGCFrame() : FunctionPass(ID)
     {
-        llvm::initializeDominatorTreeWrapperPassPass(*PassRegistry::getPassRegistry());
         tbaa_gcframe = tbaa_make_child("jtbaa_gcframe").first;
     }

 protected:
     void getAnalysisUsage(AnalysisUsage &AU) const override {
         FunctionPass::getAnalysisUsage(AU);
-        AU.addRequired<DominatorTreeWrapperPass>();
-        AU.addPreserved<DominatorTreeWrapperPass>();
         AU.setPreservesCFG();
     }

[ararslan]

If that's incorrect, perhaps the change you mentioned is better suited for a separate PR (probably by someone else...)