Implement the first half of LiveDebugVariables.

Scan the MachineFunction for DBG_VALUE instructions, and replace them with a
data structure similar to LiveIntervals. The live range of a DBG_VALUE is
determined by propagating it down the dominator tree until a new DBG_VALUE is
found. When a DBG_VALUE lives in a register, its live range is confined to the
live range of the register's value.

LiveDebugVariables runs before coalescing, so DBG_VALUEs are not artificially
extended when registers are joined.

The missing half will recreate DBG_VALUE instructions from the intervals when
register allocation is complete.

The pass is disabled by default. It can be enabled with the temporary command
line option -live-debug-variables.

llvm-svn: 120636

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugVariables.h b/llvm/lib/CodeGen/LiveDebugVariables.h
index eba4fbede27..2e4b05267dd 100644
--- a/llvm/lib/CodeGen/LiveDebugVariables.h
+++ b/llvm/lib/CodeGen/LiveDebugVariables.h
@@ -31,6 +31,7 @@ public:
   static char ID; // Pass identification, replacement for typeid
 
   LiveDebugVariables();
+  ~LiveDebugVariables();
 
   /// renameRegister - Move any user variables in OldReg to NewReg:SubIdx.
   /// @param OldReg Old virtual register that is going away.
@@ -45,9 +46,8 @@ public:
 
 private:
 
-  /// runOnMachineFunction - Analyze and remove DBG_VALUE instructions.
   virtual bool runOnMachineFunction(MachineFunction &);
-
+  virtual void releaseMemory();
   virtual void getAnalysisUsage(AnalysisUsage &) const;
 
 };