Add a mechanism for invalidating the LiveOutInfo of a PHI, and use it whenever

a block is visited before all of its predecessors.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126378 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 3 deletions

diff --git a/include/llvm/CodeGen/FunctionLoweringInfo.h b/include/llvm/CodeGen/FunctionLoweringInfo.h
index 8b1c852e4f..2d44a8beed 100644
--- a/include/llvm/CodeGen/FunctionLoweringInfo.h
+++ b/include/llvm/CodeGen/FunctionLoweringInfo.h
@@ -101,9 +101,11 @@ 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(true), KnownOne(1, 0),
+                    KnownZero(1, 0) {}
   };
 
   /// VisitedBBs - The set of basic blocks visited thus far by instruction
@@ -149,7 +151,12 @@ public:
   const LiveOutInfo *GetLiveOutRegInfo(unsigned Reg) {
     if (!LiveOutRegInfo.inBounds(Reg))
       return NULL;
-    return &LiveOutRegInfo[Reg];
+
+    const LiveOutInfo *LOI = &LiveOutRegInfo[Reg];
+    if (!LOI->IsValid)
+      return NULL;
+
+    return LOI;
   }
 
   /// AddLiveOutRegInfo - Adds LiveOutInfo for a register.
@@ -166,6 +173,14 @@ public:
     LOI.KnownZero = KnownZero;
   }
 
+  /// InvalidatePHILiveOutRegInfo - Invalidates a PHI's LiveOutInfo, to be
+  /// called when a block is visited before all of its predecessors.
+  void InvalidatePHILiveOutRegInfo(const PHINode *PN) {
+    unsigned Reg = ValueMap[PN];
+    LiveOutRegInfo.grow(Reg);
+    LiveOutRegInfo[Reg].IsValid = false;
+  }
+
   /// setByValArgumentFrameIndex - Record frame index for the byval
   /// argument.
   void setByValArgumentFrameIndex(const Argument *A, int FI);