Merge the implementations of isLoopInvariant and hasComputableLoopEvolution, and

memoize the results. This improves compile time in code which highly complex
expressions which get queried many times.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119584 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/ScalarEvolution.h

@@ -142,6 +142,16 @@ namespace llvm {
   /// they must ask this class for services.
   ///
   class ScalarEvolution : public FunctionPass {
+  public:
+    /// LoopDisposition - An enum describing the relationship between a
+    /// SCEV and a loop.
+    enum LoopDisposition {
+      LoopVariant,    ///< The SCEV is loop-variant (unknown).
+      LoopInvariant,  ///< The SCEV is loop-invariant.
+      LoopComputable  ///< The SCEV varies predictably with the loop.
+    };
+
+  private:
     /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be
     /// notified whenever a Value is deleted.
     class SCEVCallbackVH : public CallbackVH {
@@ -229,6 +239,13 @@ namespace llvm {
     std::map<const SCEV *,
              std::map<const Loop *, const SCEV *> > ValuesAtScopes;
 
+    /// LoopDispositions - Memoized computeLoopDisposition results.
+    std::map<const SCEV *,
+             std::map<const Loop *, LoopDisposition> > LoopDispositions;
+
+    /// computeLoopDisposition - Compute a LoopDisposition value.
+    LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L);
+
     /// UnsignedRanges - Memoized results from getUnsignedRange
     DenseMap<const SCEV *, ConstantRange> UnsignedRanges;
 
@@ -663,6 +680,10 @@ namespace llvm {
                               const SCEV *&LHS,
                               const SCEV *&RHS);
 
+    /// getLoopDisposition - Return the "disposition" of the given SCEV with
+    /// respect to the given loop.
+    LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L);
+
     /// isLoopInvariant - Return true if the value of the given SCEV is
     /// unchanging in the specified loop.
     bool isLoopInvariant(const SCEV *S, const Loop *L);