- 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

3 files changed, 11 insertions, 4 deletions

diff --git a/include/llvm/CodeGen/LiveVariables.h b/include/llvm/CodeGen/LiveVariables.h
index d02cfa645d..e2bed5c2ef 100644
--- a/include/llvm/CodeGen/LiveVariables.h
+++ b/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();
diff --git a/include/llvm/CodeGen/Passes.h b/include/llvm/CodeGen/Passes.h
index dd677fa5b1..412e9e3ad8 100644
--- a/include/llvm/CodeGen/Passes.h
+++ b/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();
diff --git a/include/llvm/Target/TargetOptions.h b/include/llvm/Target/TargetOptions.h
index fa739507db..6c3d88a43c 100644
--- a/include/llvm/Target/TargetOptions.h
+++ b/include/llvm/Target/TargetOptions.h
@@ -101,6 +101,11 @@ namespace llvm {
   /// DisableJumpTables - This flag indicates jump tables should not be 
   /// generated.
   extern bool DisableJumpTables;
+  
+  /// DisableCorrectBranchFolding - This flag indicates whether the instruction
+  /// selector should take care to update the CFG properly when
+  /// folding branches.
+  extern bool DisableCorrectBranchFolding;
 } // End llvm namespace
 
 #endif