Add "unknown" results for memdep, which mean "I don't know whether a dependence for the given instruction exists in the given block". This cleans up all the existing hacks in memdep which represent this concept by returning clobber with various unrelated instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133031 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 1 deletions

diff --git a/include/llvm/Analysis/MemoryDependenceAnalysis.h b/include/llvm/Analysis/MemoryDependenceAnalysis.h
index b56fe08e23..34860e712f 100644
--- a/include/llvm/Analysis/MemoryDependenceAnalysis.h
+++ b/include/llvm/Analysis/MemoryDependenceAnalysis.h
@@ -90,18 +90,27 @@ namespace llvm {
     /// get methods: These are static ctor methods for creating various
     /// MemDepResult kinds.
     static MemDepResult getDef(Instruction *Inst) {
+      assert(Inst && "Def requires inst");
       return MemDepResult(PairTy(Inst, Def));
     }
     static MemDepResult getClobber(Instruction *Inst) {
+      assert(Inst && "Clobber requires inst");
       return MemDepResult(PairTy(Inst, Clobber));
     }
     static MemDepResult getNonLocal() {
       return MemDepResult(PairTy(0, NonLocal));
     }
+    static MemDepResult getUnknown() {
+      return MemDepResult(PairTy(0, Clobber));
+    }
 
     /// isClobber - Return true if this MemDepResult represents a query that is
     /// a instruction clobber dependency.
-    bool isClobber() const { return Value.getInt() == Clobber; }
+    bool isClobber() const { return Value.getInt() == Clobber && getInst(); }
+
+    /// isUnknown - Return true if this MemDepResult represents a query which
+    /// cannot and/or will not be computed.
+    bool isUnknown() const { return Value.getInt() == Clobber && !getInst(); }
 
     /// isDef - Return true if this MemDepResult represents a query that is
     /// a instruction definition dependency.