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

[Joshua Cao via Phabricator via llvm-commits]

caojoshua updated this revision to Diff 510313.
caojoshua added a comment.

Convert more sign extend to zero extend


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
@@ -8046,6 +8046,12 @@
   if (!Extend)
     return getAddExpr(ExitCount, getOne(ExitCountType));
 
+  ConstantRange ExitCountRange =
+      getRangeRef(ExitCount, RangeSignHint::HINT_RANGE_UNSIGNED);
+  if (!ExitCountRange.contains(
+          APInt::getMaxValue(ExitCountRange.getBitWidth())))
+    return getAddExpr(ExitCount, getOne(ExitCountType));
+
   auto *WiderType = Type::getIntNTy(ExitCountType->getContext(),
                                     1 + ExitCountType->getScalarSizeInBits());
   return getAddExpr(getNoopOrZeroExtend(ExitCount, WiderType),
@@ -8228,15 +8234,14 @@
     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);
 
@@ -323,8 +323,8 @@
       const SCEV *TripCount =
           computeTripCount(*AR->getLoop(), *Sizes.back(), SE);
       Type *WiderType = SE.getWiderType(RefCost->getType(), TripCount->getType());
-      RefCost = SE.getMulExpr(SE.getNoopOrAnyExtend(RefCost, WiderType),
-                              SE.getNoopOrAnyExtend(TripCount, WiderType));
+      RefCost = SE.getMulExpr(SE.getNoopOrZeroExtend(RefCost, WiderType),
+                              SE.getNoopOrZeroExtend(TripCount, WiderType));
     }
 
     LLVM_DEBUG(dbgs().indent(4)
@@ -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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