Allow loop unrolling to get known trip counts from ScalarEvolution.

SCEV unrolling can unroll loops with arbitrary induction variables. It
is a prerequisite for -disable-iv-rewrite performance. It is also
easily handles loops of arbitrary structure including multiple exits
and is generally more robust.

This is under a temporary option to avoid affecting default
behavior for the next couple of weeks. It is needed so that I can
checkin unit tests for updateUnloop.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137384 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 1 deletions

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index c621bec86a..6e30b31771 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -507,7 +507,8 @@ namespace llvm {
     /// FoundLHS, and FoundRHS is true.
     bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
                                      const SCEV *LHS, const SCEV *RHS,
-                                     const SCEV *FoundLHS, const SCEV *FoundRHS);
+                                     const SCEV *FoundLHS,
+                                     const SCEV *FoundRHS);
 
     /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
     /// in the header of its containing loop, we know the loop executes a
@@ -710,6 +711,18 @@ namespace llvm {
     bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
                                      const SCEV *LHS, const SCEV *RHS);
 
+    /// getSmallConstantTripCount - Returns the maximum trip count of this loop
+    /// as a normal unsigned value, if possible. Returns 0 if the trip count is
+    /// unknown or not constant.
+    unsigned getSmallConstantTripCount(Loop *L, BasicBlock *ExitBlock);
+
+    /// getSmallConstantTripMultiple - Returns the largest constant divisor of
+    /// the trip count of this loop as a normal unsigned value, if
+    /// possible. This means that the actual trip count is always a multiple of
+    /// the returned value (don't forget the trip count could very well be zero
+    /// as well!).
+    unsigned getSmallConstantTripMultiple(Loop *L, BasicBlock *ExitBlock);
+
     // getExitCount - Get the expression for the number of loop iterations for
     // which this loop is guaranteed not to exit via ExitingBlock. Otherwise
     // return SCEVCouldNotCompute.