Merge information about the number of zero, one, and sign bits of live-out registers

at phis. This enables us to eliminate a lot of pointless zexts during the DAGCombine
phase. This fixes <rdar://problem/8760114>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126170 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 2 deletions

diff --git a/include/llvm/CodeGen/FunctionLoweringInfo.h b/include/llvm/CodeGen/FunctionLoweringInfo.h
index 27631b7ea1..6bc10dfaa3 100644
--- a/include/llvm/CodeGen/FunctionLoweringInfo.h
+++ b/include/llvm/CodeGen/FunctionLoweringInfo.h
@@ -101,14 +101,30 @@ public:
 #endif
 
   struct LiveOutInfo {
-    unsigned NumSignBits;
+    unsigned NumSignBits : 31;
+    bool IsValid : 1;
     APInt KnownOne, KnownZero;
-    LiveOutInfo() : NumSignBits(0), KnownOne(1, 0), KnownZero(1, 0) {}
+    LiveOutInfo() : NumSignBits(0), IsValid(false), KnownOne(1, 0),
+                    KnownZero(1, 0) {}
   };
   
   /// LiveOutRegInfo - Information about live out vregs.
   IndexedMap<LiveOutInfo, VirtReg2IndexFunctor> LiveOutRegInfo;
 
+  /// VisitedBBs - Basic blocks that have been visited by reverse postorder.
+  DenseSet<const BasicBlock*> VisitedBBs;
+
+  /// AllPredsVisited - Tracks whether all predecessors of the current basic
+  /// block have already been visited.
+  bool AllPredsVisited;
+
+  /// PHIDestRegs - Virtual registers that are the destinations of PHIs.
+  DenseSet<unsigned> PHIDestRegs;
+
+  /// PHISrcToDestMap - Maps the virtual register defining a PHI's source to the
+  /// virtual register defining its destination.
+  DenseMap<unsigned, unsigned> PHISrcToDestMap;
+
   /// PHINodesToUpdate - A list of phi instructions whose operand list will
   /// be updated after processing the current basic block.
   /// TODO: This isn't per-function state, it's per-basic-block state. But