- Fix SelectionDAG to generate correct CFGs.

- Add a basic machine-level dead block eliminator.

These two have to go together, since many other parts of the code generator are unable to handle the unreachable blocks otherwise created.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54333 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveVariables.cpp

@@ -29,6 +29,7 @@
 #include "llvm/CodeGen/LiveVariables.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
@@ -43,6 +44,12 @@ using namespace llvm;
 char LiveVariables::ID = 0;
 static RegisterPass<LiveVariables> X("livevars", "Live Variable Analysis");
 
+
+void LiveVariables::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addRequiredID(UnreachableMachineBlockElimID);
+  AU.setPreservesAll();
+}
+
 void LiveVariables::VarInfo::dump() const {
   cerr << "  Alive in blocks: ";
   for (unsigned i = 0, e = AliveBlocks.size(); i != e; ++i)