[SCEV] Use const Loop *L instead of Loop *L. NFC

Use const pointer in the trip count and trip multiple calculations.

Patch by Huihui Zhang <huihuiz@codeaurora.org>

llvm-svn: 298161

llvm/include/llvm/Analysis/ScalarEvolution.h

@@ -1296,7 +1296,7 @@ public:
   ///
   /// Implemented in terms of the \c getSmallConstantTripCount overload with
   /// the single exiting block passed to it. See that routine for details.
-  unsigned getSmallConstantTripCount(Loop *L);
+  unsigned getSmallConstantTripCount(const Loop *L);
 
   /// Returns the maximum trip count of this loop as a normal unsigned
   /// value. Returns 0 if the trip count is unknown or not constant. This
@@ -1305,12 +1305,12 @@ public:
   /// before taking the branch. For loops with multiple exits, it may not be
   /// the number times that the loop header executes if the loop exits
   /// prematurely via another branch.
-  unsigned getSmallConstantTripCount(Loop *L, BasicBlock *ExitingBlock);
+  unsigned getSmallConstantTripCount(const Loop *L, BasicBlock *ExitingBlock);
 
   /// Returns the upper bound of the loop trip count as a normal unsigned
   /// value.
   /// Returns 0 if the trip count is unknown or not constant.
-  unsigned getSmallConstantMaxTripCount(Loop *L);
+  unsigned getSmallConstantMaxTripCount(const Loop *L);
 
   /// Returns the largest constant divisor of the trip count of the
   /// loop if it is a single-exit loop and we can compute a small maximum for
@@ -1318,7 +1318,7 @@ public:
   ///
   /// Implemented in terms of the \c getSmallConstantTripMultiple overload with
   /// the single exiting block passed to it. See that routine for details.
-  unsigned getSmallConstantTripMultiple(Loop *L);
+  unsigned getSmallConstantTripMultiple(const Loop *L);
 
   /// 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
@@ -1326,12 +1326,13 @@ public:
   /// count could very well be zero as well!). As explained in the comments
   /// for getSmallConstantTripCount, this assumes that control exits the loop
   /// via ExitingBlock.
-  unsigned getSmallConstantTripMultiple(Loop *L, BasicBlock *ExitingBlock);
+  unsigned getSmallConstantTripMultiple(const Loop *L,
+                                        BasicBlock *ExitingBlock);
 
   /// Get the expression for the number of loop iterations for which this loop
   /// is guaranteed not to exit via ExitingBlock. Otherwise return
   /// SCEVCouldNotCompute.
-  const SCEV *getExitCount(Loop *L, BasicBlock *ExitingBlock);
+  const SCEV *getExitCount(const Loop *L, BasicBlock *ExitingBlock);
 
   /// If the specified loop has a predictable backedge-taken count, return it,
   /// otherwise return a SCEVCouldNotCompute object. The backedge-taken count

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -5449,7 +5449,7 @@ static unsigned getConstantTripCount(const SCEVConstant *ExitCount) {
   return ((unsigned)ExitConst->getZExtValue()) + 1;
 }
 
-unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L) {
+unsigned ScalarEvolution::getSmallConstantTripCount(const Loop *L) {
   if (BasicBlock *ExitingBB = L->getExitingBlock())
     return getSmallConstantTripCount(L, ExitingBB);
 
@@ -5457,7 +5457,7 @@ unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L) {
   return 0;
 }
 
-unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
+unsigned ScalarEvolution::getSmallConstantTripCount(const Loop *L,
                                                     BasicBlock *ExitingBlock) {
   assert(ExitingBlock && "Must pass a non-null exiting block!");
   assert(L->isLoopExiting(ExitingBlock) &&
@@ -5467,13 +5467,13 @@ unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
   return getConstantTripCount(ExitCount);
 }
 
-unsigned ScalarEvolution::getSmallConstantMaxTripCount(Loop *L) {
+unsigned ScalarEvolution::getSmallConstantMaxTripCount(const Loop *L) {
   const auto *MaxExitCount =
       dyn_cast<SCEVConstant>(getMaxBackedgeTakenCount(L));
   return getConstantTripCount(MaxExitCount);
 }
 
-unsigned ScalarEvolution::getSmallConstantTripMultiple(Loop *L) {
+unsigned ScalarEvolution::getSmallConstantTripMultiple(const Loop *L) {
   if (BasicBlock *ExitingBB = L->getExitingBlock())
     return getSmallConstantTripMultiple(L, ExitingBB);
 
@@ -5494,7 +5494,7 @@ unsigned ScalarEvolution::getSmallConstantTripMultiple(Loop *L) {
 /// As explained in the comments for getSmallConstantTripCount, this assumes
 /// that control exits the loop via ExitingBlock.
 unsigned
-ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
+ScalarEvolution::getSmallConstantTripMultiple(const Loop *L,
                                               BasicBlock *ExitingBlock) {
   assert(ExitingBlock && "Must pass a non-null exiting block!");
   assert(L->isLoopExiting(ExitingBlock) &&
@@ -5529,7 +5529,8 @@ ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
 /// Get the expression for the number of loop iterations for which this loop is
 /// guaranteed not to exit via ExitingBlock. Otherwise return
 /// SCEVCouldNotCompute.
-const SCEV *ScalarEvolution::getExitCount(Loop *L, BasicBlock *ExitingBlock) {
+const SCEV *ScalarEvolution::getExitCount(const Loop *L,
+                                          BasicBlock *ExitingBlock) {
   return getBackedgeTakenInfo(L).getExact(ExitingBlock, this);
 }