- 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

include/llvm/CodeGen/LiveVariables.h

@@ -247,10 +247,8 @@ public:
     assert(Removed && "Register is not defined by this instruction!");
     return true;
   }
-
-  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
-    AU.setPreservesAll();
-  }
+  
+  void getAnalysisUsage(AnalysisUsage &AU) const;
 
   virtual void releaseMemory() {
     VirtRegInfo.clear();

include/llvm/CodeGen/Passes.h

@@ -71,6 +71,10 @@ namespace llvm {
   /// register allocators.
   extern const PassInfo *const TwoAddressInstructionPassID;
 
+  /// UnreachableMachineBlockElimination pass - This pass removes unreachable
+  /// machine basic blocks.
+  extern const PassInfo *const UnreachableMachineBlockElimID;
+
   /// Creates a register allocator as the user specified on the command line.
   ///
   FunctionPass *createRegisterAllocator();