[PATCH] D147117: [SCEV] When computing trip count, only zext if necessary

[Joshua Cao via Phabricator via llvm-commits]

caojoshua updated this revision to Diff 509561.
caojoshua added a comment.

Use `willNotOverflow()`.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D147117/new/

https://reviews.llvm.org/D147117

Files:
  llvm/lib/Analysis/LoopCacheAnalysis.cpp
  llvm/lib/Analysis/ScalarEvolution.cpp


Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -8043,8 +8043,9 @@
   auto *ExitCountType = ExitCount->getType();
   assert(ExitCountType->isIntegerTy());
 
-  if (!Extend)
-    return getAddExpr(ExitCount, getOne(ExitCountType));
+  const SCEV *One = getOne(ExitCountType);
+  if (!Extend || willNotOverflow(Instruction::Add, false, ExitCount, One))
+    return getAddExpr(ExitCount, One);
 
   auto *WiderType = Type::getIntNTy(ExitCountType->getContext(),
                                     1 + ExitCountType->getScalarSizeInBits());
@@ -8228,15 +8229,14 @@
     return 1;
 
   // Get the trip count
-  const SCEV *TCExpr = getTripCountFromExitCount(ExitCount);
+  const SCEV *TCExpr = getTripCountFromExitCount(applyLoopGuards(ExitCount, L));
 
   const SCEVConstant *TC = dyn_cast<SCEVConstant>(TCExpr);
   if (!TC)
     // Attempt to factor more general cases. Returns the greatest power of
     // two divisor. If overflow happens, the trip count expression is still
     // divisible by the greatest power of 2 divisor returned.
-    return 1U << std::min((uint32_t)31,
-                          GetMinTrailingZeros(applyLoopGuards(TCExpr, L)));
+    return 1U << std::min((uint32_t)31, GetMinTrailingZeros(TCExpr));
 
   ConstantInt *Result = TC->getValue();
 
Index: llvm/lib/Analysis/LoopCacheAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/LoopCacheAnalysis.cpp
+++ llvm/lib/Analysis/LoopCacheAnalysis.cpp
@@ -297,7 +297,7 @@
     Type *WiderType = SE.getWiderType(Stride->getType(), TripCount->getType());
     const SCEV *CacheLineSize = SE.getConstant(WiderType, CLS);
     Stride = SE.getNoopOrAnyExtend(Stride, WiderType);
-    TripCount = SE.getNoopOrAnyExtend(TripCount, WiderType);
+    TripCount = SE.getNoopOrZeroExtend(TripCount, WiderType);
     const SCEV *Numerator = SE.getMulExpr(Stride, TripCount);
     RefCost = SE.getUDivExpr(Numerator, CacheLineSize);
 
@@ -334,7 +334,7 @@
 
   // Attempt to fold RefCost into a constant.
   if (auto ConstantCost = dyn_cast<SCEVConstant>(RefCost))
-    return ConstantCost->getValue()->getSExtValue();
+    return ConstantCost->getValue()->getZExtValue();
 
   LLVM_DEBUG(dbgs().indent(4)
              << "RefCost is not a constant! Setting to RefCost=InvalidCost "


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