Fix liveness calculation when splitting critical edges during PHI elimination.

- Edges are split before any phis are eliminated, so the code is SSA.

- Create a proper IR BasicBlock for the split edges.

- LiveVariables::addNewBlock now has same syntax as
  MachineDominatorTree::addNewBlock. Algorithm calculates predecessor live-out
  set rather than successor live-in set.

This feature still causes some miscompilations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86867 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/CodeGen/PHIElimination.h b/lib/CodeGen/PHIElimination.h
index 8188440c89..edc2d36670 100644
--- a/lib/CodeGen/PHIElimination.h
+++ b/lib/CodeGen/PHIElimination.h
@@ -90,7 +90,7 @@ namespace llvm {
     void analyzePHINodes(const MachineFunction& Fn);
 
     /// Split critical edges where necessary for good coalescer performance.
-    void SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB);
+    bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB);
 
     /// isLiveOut - Determine if Reg is live out from MBB, when not
     /// considering PHI nodes. This means that Reg is either killed by
@@ -98,6 +98,12 @@ namespace llvm {
     bool isLiveOut(unsigned Reg, const MachineBasicBlock &MBB,
                    LiveVariables &LV);
 
+    /// isLiveIn - Determine if Reg is live in to MBB, not considering PHI
+    /// source registers. This means that Reg is either killed by MBB or passes
+    /// through it.
+    bool isLiveIn(unsigned Reg, const MachineBasicBlock &MBB,
+                  LiveVariables &LV);
+
     /// SplitCriticalEdge - Split a critical edge from A to B by
     /// inserting a new MBB. Update branches in A and PHI instructions
     /// in B. Return the new block.