From beda6ab879e35b6f7d998da980b30e3844d3bbeb Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Wed, 20 Feb 2013 23:08:26 +0000
Subject: Copy single reaching defs directly into the LiveInterval.

When findReachingDefs() finds that only one value can reach the basic
block, just copy the work list of visited blocks directly into the live
interval.

Sort the block list and use a LiveRangeUpdater to make the bulk add
fast.

When multiple reaching defs are found, transfer the work list to the
updateSSA() work list as before. Also use LiveRangeUpdater in
updateLiveIns() following updateSSA().

This makes live interval analysis more than 3x faster on one huge test
case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175685 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/LiveRangeCalc.h | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

(limited to 'lib/CodeGen/LiveRangeCalc.h')

diff --git a/lib/CodeGen/LiveRangeCalc.h b/lib/CodeGen/LiveRangeCalc.h
index 909829b228..57cab7b342 100644
--- a/lib/CodeGen/LiveRangeCalc.h
+++ b/lib/CodeGen/LiveRangeCalc.h
@@ -34,6 +34,7 @@ template <class NodeT> class DomTreeNodeBase;
 typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
 
 class LiveRangeCalc {
+  const MachineFunction *MF;
   const MachineRegisterInfo *MRI;
   SlotIndexes *Indexes;
   MachineDominatorTree *DomTree;
@@ -100,17 +101,20 @@ class LiveRangeCalc {
   /// used to add entries directly.
   SmallVector<LiveInBlock, 16> LiveIn;
 
-  /// findReachingDefs - Assuming that LI is live-in to KillMBB and killed at
-  /// Kill, search for values that can reach KillMBB.  All blocks that need LI
-  /// to be live-in are added to LiveIn.  If a unique reaching def is found,
-  /// its value is returned, if Kill is jointly dominated by multiple values,
-  /// NULL is returned.
+  /// Assuming that LI is live-in to KillMBB and killed at Kill, find the set
+  /// of defs that can reach it.
+  ///
+  /// If only one def can reach Kill, all paths from the def to kill are added
+  /// to LI, and the function returns true.
+  ///
+  /// If multiple values can reach Kill, the blocks that need LI to be live in
+  /// are added to the LiveIn array, and the function returns false.
   ///
   /// PhysReg, when set, is used to verify live-in lists on basic blocks.
-  VNInfo *findReachingDefs(LiveInterval *LI,
-                           MachineBasicBlock *KillMBB,
-                           SlotIndex Kill,
-                           unsigned PhysReg);
+  bool findReachingDefs(LiveInterval *LI,
+                        MachineBasicBlock *KillMBB,
+                        SlotIndex Kill,
+                        unsigned PhysReg);
 
   /// updateSSA - Compute the values that will be live in to all requested
   /// blocks in LiveIn.  Create PHI-def values as required to preserve SSA form.
@@ -119,12 +123,11 @@ class LiveRangeCalc {
   /// blocks.  No values are read from the live ranges.
   void updateSSA();
 
-  /// updateLiveIns - Add liveness as specified in the LiveIn vector, using VNI
-  /// as a wildcard value for LiveIn entries without a value.
-  void updateLiveIns(VNInfo *VNI);
+  /// Add liveness as specified in the LiveIn vector.
+  void updateLiveIns();
 
 public:
-  LiveRangeCalc() : MRI(0), Indexes(0), DomTree(0), Alloc(0) {}
+  LiveRangeCalc() : MF(0), MRI(0), Indexes(0), DomTree(0), Alloc(0) {}
 
   //===--------------------------------------------------------------------===//
   // High-level interface.
-- 
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