Completely eliminate VNInfo flags.

The 'unused' state of a value number can be represented as an invalid
def SlotIndex. This also exposed code that shouldn't have been looking
at unused value VNInfos.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161258 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LiveInterval.h

@@ -40,13 +40,6 @@ namespace llvm {
   /// definition and use points.
   ///
   class VNInfo {
-  private:
-    enum {
-      IS_UNUSED       = 1
-    };
-
-    unsigned char flags;
-
   public:
     typedef BumpPtrAllocator Allocator;
 
@@ -58,29 +51,19 @@ namespace llvm {
 
     /// VNInfo constructor.
     VNInfo(unsigned i, SlotIndex d)
-      : flags(0), id(i), def(d)
+      : id(i), def(d)
     { }
 
     /// VNInfo construtor, copies values from orig, except for the value number.
     VNInfo(unsigned i, const VNInfo &orig)
-      : flags(orig.flags), id(i), def(orig.def)
+      : id(i), def(orig.def)
     { }
 
     /// Copy from the parameter into this VNInfo.
     void copyFrom(VNInfo &src) {
-      flags = src.flags;
       def = src.def;
     }
 
-    /// Used for copying value number info.
-    unsigned getFlags() const { return flags; }
-    void setFlags(unsigned flags) { this->flags = flags; }
-
-    /// Merge flags from another VNInfo
-    void mergeFlags(const VNInfo *VNI) {
-      flags = (flags | VNI->flags) & ~IS_UNUSED;
-    }
-
     /// Returns true if this value is defined by a PHI instruction (or was,
     /// PHI instrucions may have been eliminated).
     /// PHI-defs begin at a block boundary, all other defs begin at register or
@@ -88,14 +71,10 @@ namespace llvm {
     bool isPHIDef() const { return def.isBlock(); }
 
     /// Returns true if this value is unused.
-    bool isUnused() const { return flags & IS_UNUSED; }
-    /// Set the "is unused" flag on this value.
-    void setIsUnused(bool unused) {
-      if (unused)
-        flags |= IS_UNUSED;
-      else
-        flags &= ~IS_UNUSED;
-    }
+    bool isUnused() const { return !def.isValid(); }
+
+    /// Mark this value as unused.
+    void markUnused() { def = SlotIndex(); }
   };
 
   /// LiveRange structure - This represents a simple register range in the

lib/CodeGen/LiveInterval.cpp

@@ -160,7 +160,7 @@ void LiveInterval::markValNoForDeletion(VNInfo *ValNo) {
       valnos.pop_back();
     } while (!valnos.empty() && valnos.back()->isUnused());
   } else {
-    ValNo->setIsUnused(true);
+    ValNo->markUnused();
   }
 }
 
@@ -667,9 +667,6 @@ VNInfo* LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
     }
   }
 
-  // Merge the relevant flags.
-  V2->mergeFlags(V1);
-
   // Now that V1 is dead, remove it.
   markValNoForDeletion(V1);
 

lib/CodeGen/LiveIntervalAnalysis.cpp

@@ -706,7 +706,7 @@ bool LiveIntervals::shrinkToUses(LiveInterval *li,
       continue;
     if (VNI->isPHIDef()) {
       // This is a dead PHI. Remove it.
-      VNI->setIsUnused(true);
+      VNI->markUnused();
       NewLI.removeRange(*LII);
       DEBUG(dbgs() << "Dead PHI at " << VNI->def << " may separate interval\n");
       CanSeparate = true;