[llvm] r330362 - Refine the loop rotation's API

[Jin Lin via llvm-commits]

Author: jinlin
Date: Thu Apr 19 13:29:43 2018
New Revision: 330362

URL: http://llvm.org/viewvc/llvm-project?rev=330362&view=rev
Log:
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

Modified:
    llvm/trunk/include/llvm/Transforms/Utils/LoopRotationUtils.h
    llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
    llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp

Modified: llvm/trunk/include/llvm/Transforms/Utils/LoopRotationUtils.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/LoopRotationUtils.h?rev=330362&r1=330361&r2=330362&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/LoopRotationUtils.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/LoopRotationUtils.h Thu Apr 19 13:29:43 2018
@@ -24,11 +24,16 @@ class ScalarEvolution;
 struct SimplifyQuery;
 class TargetTransformInfo;
 
-/// \brief Convert a loop into a loop with bottom test.
-bool LoopRotation(Loop *L, unsigned MaxHeaderSize, LoopInfo *LI,
-                  const TargetTransformInfo *TTI, AssumptionCache *AC,
-                  DominatorTree *DT, ScalarEvolution *SE,
-                  const SimplifyQuery &SQ);
+/// \brief Convert a loop into a loop with bottom test. It may
+/// perform loop latch simplication as well if the flag RotationOnly
+/// is false. The flag Threshold represents the size threshold of the loop
+/// header. If the loop header's size exceeds the threshold, the loop rotation
+/// will give up. The flag IsUtilMode controls the heuristic used in the
+/// LoopRotation. If it is true, the profitability heuristic will be ignored.
+bool LoopRotation(Loop *L, LoopInfo *LI, const TargetTransformInfo *TTI,
+                  AssumptionCache *AC, DominatorTree *DT, ScalarEvolution *SE,
+                  const SimplifyQuery &SQ, bool RotationOnly,
+                  unsigned Threshold, bool IsUtilMode);
 
 } // namespace llvm
 

Modified: llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp?rev=330362&r1=330361&r2=330362&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopRotation.cpp Thu Apr 19 13:29:43 2018
@@ -40,8 +40,8 @@ PreservedAnalyses LoopRotatePass::run(Lo
   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);
   }
 };
 }

Modified: llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp?rev=330362&r1=330361&r2=330362&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp Thu Apr 19 13:29:43 2018
@@ -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, boo
 
   // 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);
 }