Refine the loop rotation's API

Summary:
The following changes addresses the following two issues.

1) The existing loop rotation pass contains both loop latch simplification and loop rotation. So one flag RotationOnly is added to be passed to the loop rotation pass.
2) The threshold value is initialized with MAX_UINT since the loop rotation utility should not have threshold limit.

Reviewers: dmgreen, efriedma

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D45582

llvm-svn: 330362

2 files changed, 21 insertions, 12 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index 6ea9c2bce4f..eeaad39dc1d 100644
--- a/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -40,8 +40,8 @@ PreservedAnalyses LoopRotatePass::run(Loop &L, LoopAnalysisManager &AM,
   const DataLayout &DL = L.getHeader()->getModule()->getDataLayout();
   const SimplifyQuery SQ = getBestSimplifyQuery(AR, DL);
 
-  bool Changed =
-      LoopRotation(&L, Threshold, &AR.LI, &AR.TTI, &AR.AC, &AR.DT, &AR.SE, SQ);
+  bool Changed = LoopRotation(&L, &AR.LI, &AR.TTI, &AR.AC, &AR.DT, &AR.SE, SQ,
+                              false, Threshold, false);
 
   if (!Changed)
     return PreservedAnalyses::all();
@@ -84,7 +84,8 @@ public:
     auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
     auto *SE = SEWP ? &SEWP->getSE() : nullptr;
     const SimplifyQuery SQ = getBestSimplifyQuery(*this, F);
-    return LoopRotation(L, MaxHeaderSize, LI, TTI, AC, DT, SE, SQ);
+    return LoopRotation(L, LI, TTI, AC, DT, SE, SQ, false, MaxHeaderSize,
+                        false);
   }
 };
 }
diff --git a/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp b/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
index 529a0ec3525..d96c1014877 100644
--- a/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
@@ -54,13 +54,16 @@ class LoopRotate {
   DominatorTree *DT;
   ScalarEvolution *SE;
   const SimplifyQuery &SQ;
+  bool RotationOnly;
+  bool IsUtilMode;
 
 public:
   LoopRotate(unsigned MaxHeaderSize, LoopInfo *LI,
              const TargetTransformInfo *TTI, AssumptionCache *AC,
-             DominatorTree *DT, ScalarEvolution *SE, const SimplifyQuery &SQ)
+             DominatorTree *DT, ScalarEvolution *SE, const SimplifyQuery &SQ,
+             bool RotationOnly, bool IsUtilMode)
       : MaxHeaderSize(MaxHeaderSize), LI(LI), TTI(TTI), AC(AC), DT(DT), SE(SE),
-        SQ(SQ) {}
+        SQ(SQ), RotationOnly(RotationOnly), IsUtilMode(IsUtilMode) {}
   bool processLoop(Loop *L);
 
 private:
@@ -219,7 +222,7 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
 
   // Rotate if either the loop latch does *not* exit the loop, or if the loop
   // latch was just simplified. Or if we think it will be profitable.
-  if (L->isLoopExiting(OrigLatch) && !SimplifiedLatch &&
+  if (L->isLoopExiting(OrigLatch) && !SimplifiedLatch && IsUtilMode == false &&
       !shouldRotateLoopExitingLatch(L))
     return false;
 
@@ -604,10 +607,13 @@ bool LoopRotate::processLoop(Loop *L) {
   // Save the loop metadata.
   MDNode *LoopMD = L->getLoopID();
 
+  bool SimplifiedLatch = false;
+
   // Simplify the loop latch before attempting to rotate the header
   // upward. Rotation may not be needed if the loop tail can be folded into the
   // loop exit.
-  bool SimplifiedLatch = simplifyLoopLatch(L);
+  if (!RotationOnly)
+    SimplifiedLatch = simplifyLoopLatch(L);
 
   bool MadeChange = rotateLoop(L, SimplifiedLatch);
   assert((!MadeChange || L->isLoopExiting(L->getLoopLatch())) &&
@@ -623,11 +629,13 @@ bool LoopRotate::processLoop(Loop *L) {
 
 
 /// The utility to convert a loop into a loop with bottom test.
-bool llvm::LoopRotation(Loop *L, unsigned MaxHeaderSize, LoopInfo *LI,
-                        const TargetTransformInfo *TTI, AssumptionCache *AC,
-                        DominatorTree *DT, ScalarEvolution *SE,
-                        const SimplifyQuery &SQ) {
-  LoopRotate LR(MaxHeaderSize, LI, TTI, AC, DT, SE, SQ);
+bool llvm::LoopRotation(Loop *L, LoopInfo *LI, const TargetTransformInfo *TTI,
+                        AssumptionCache *AC, DominatorTree *DT,
+                        ScalarEvolution *SE, const SimplifyQuery &SQ,
+                        bool RotationOnly = true,
+                        unsigned Threshold = unsigned(-1),
+                        bool IsUtilMode = true) {
+  LoopRotate LR(Threshold, LI, TTI, AC, DT, SE, SQ, RotationOnly, IsUtilMode);
 
   return LR.processLoop(L);
 }