Fix for PR929. The PHI nodes were being gone through for each instruction

in a successor block for every block...resulting in some O(N^k) algorithm
which wasn't very good for performance. Calculating this information up
front and keeping it in a map made it much faster.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30697 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 1 deletions

diff --git a/include/llvm/CodeGen/LiveVariables.h b/include/llvm/CodeGen/LiveVariables.h
index a61eca89c1..95114c0b70 100644
--- a/include/llvm/CodeGen/LiveVariables.h
+++ b/include/llvm/CodeGen/LiveVariables.h
@@ -39,7 +39,7 @@ class MRegisterInfo;
 class LiveVariables : public MachineFunctionPass {
 public:
   /// VarInfo - This represents the regions where a virtual register is live in
-  /// the program.  We represent this with three difference pieces of
+  /// the program.  We represent this with three different pieces of
   /// information: the instruction that uniquely defines the value, the set of
   /// blocks the instruction is live into and live out of, and the set of 
   /// non-phi instructions that are the last users of the value.
@@ -136,9 +136,19 @@ private:   // Intermediate data structures
   MachineInstr **PhysRegInfo;
   bool          *PhysRegUsed;
 
+  typedef std::map<const MachineBasicBlock*,
+                   std::vector<unsigned> > PHIVarInfoMap;
+
+  PHIVarInfoMap PHIVarInfo;
+
   void HandlePhysRegUse(unsigned Reg, MachineInstr *MI);
   void HandlePhysRegDef(unsigned Reg, MachineInstr *MI);
 
+  /// analyzePHINodes - Gather information about the PHI nodes in here. In
+  /// particular, we want to map the variable information of a virtual
+  /// register which is used in a PHI node. We map that to the BB the vreg
+  /// is coming from.
+  void analyzePHINodes(const MachineFunction& Fn);
 public:
 
   virtual bool runOnMachineFunction(MachineFunction &MF);