[Delinearization] Remove tryDelinearizeFixedSizeImpl (llvm#169046)

`tryDelinearizeFixedSizeImpl` is a heuristic function relying on GEP's
type information. Using these information to drive an optimization
heuristic is not allowed, so this function should be removed. As llvm#161822
and llvm#164798 have eliminated all calls to this, this patch removes the
function itself.

Author: kasuga-fj

llvm/include/llvm/Analysis/Delinearization.h

@@ -133,9 +133,8 @@ bool findFixedSizeArrayDimensions(ScalarEvolution &SE, const SCEV *Expr,
 /// terms exist in the \p Expr. In other words, it assumes that the all step
 /// values are constant.
 ///
-/// This function is intended to replace getIndexExpressionsFromGEP and
-/// tryDelinearizeFixedSizeImpl. They rely on the GEP source element type so
-/// that they will be removed in the future.
+/// This function is intended to replace getIndexExpressionsFromGEP. They rely
+/// on the GEP source element type so that will be removed in the future.
 bool delinearizeFixedSizeArray(ScalarEvolution &SE, const SCEV *Expr,
                                SmallVectorImpl<const SCEV *> &Subscripts,
                                SmallVectorImpl<const SCEV *> &Sizes,
@@ -155,17 +154,6 @@ bool getIndexExpressionsFromGEP(ScalarEvolution &SE,
                                 SmallVectorImpl<const SCEV *> &Subscripts,
                                 SmallVectorImpl<int> &Sizes);
 
-/// Implementation of fixed size array delinearization. Try to delinearize
-/// access function for a fixed size multi-dimensional array, by deriving
-/// subscripts from GEP instructions. Returns true upon success and false
-/// otherwise. \p Inst is the load/store instruction whose pointer operand is
-/// the one we want to delinearize. \p AccessFn is its corresponding SCEV
-/// expression w.r.t. the surrounding loop.
-bool tryDelinearizeFixedSizeImpl(ScalarEvolution *SE, Instruction *Inst,
-                                 const SCEV *AccessFn,
-                                 SmallVectorImpl<const SCEV *> &Subscripts,
-                                 SmallVectorImpl<int> &Sizes);
-
 struct DelinearizationPrinterPass
     : public PassInfoMixin<DelinearizationPrinterPass> {
   explicit DelinearizationPrinterPass(raw_ostream &OS);

llvm/include/llvm/Analysis/DependenceAnalysis.h

@@ -773,8 +773,8 @@ class DependenceInfo {
                       SmallVectorImpl<Subscript> &Pair);
 
   /// Tries to delinearize \p Src and \p Dst access functions for a fixed size
-  /// multi-dimensional array. Calls tryDelinearizeFixedSizeImpl() to
-  /// delinearize \p Src and \p Dst separately,
+  /// multi-dimensional array. Calls delinearizeFixedSizeArray() to delinearize
+  /// \p Src and \p Dst separately,
   bool tryDelinearizeFixedSize(Instruction *Src, Instruction *Dst,
                                const SCEV *SrcAccessFn, const SCEV *DstAccessFn,
                                SmallVectorImpl<const SCEV *> &SrcSubscripts,

llvm/lib/Analysis/Delinearization.cpp

@@ -704,44 +704,6 @@ bool llvm::getIndexExpressionsFromGEP(ScalarEvolution &SE,
   return !Subscripts.empty();
 }
 
-bool llvm::tryDelinearizeFixedSizeImpl(
-    ScalarEvolution *SE, Instruction *Inst, const SCEV *AccessFn,
-    SmallVectorImpl<const SCEV *> &Subscripts, SmallVectorImpl<int> &Sizes) {
-  Value *SrcPtr = getLoadStorePointerOperand(Inst);
-
-  // Check the simple case where the array dimensions are fixed size.
-  auto *SrcGEP = dyn_cast<GetElementPtrInst>(SrcPtr);
-  if (!SrcGEP)
-    return false;
-
-  getIndexExpressionsFromGEP(*SE, SrcGEP, Subscripts, Sizes);
-
-  // Check that the two size arrays are non-empty and equal in length and
-  // value.
-  // TODO: it would be better to let the caller to clear Subscripts, similar
-  // to how we handle Sizes.
-  if (Sizes.empty() || Subscripts.size() <= 1) {
-    Subscripts.clear();
-    return false;
-  }
-
-  // Check that for identical base pointers we do not miss index offsets
-  // that have been added before this GEP is applied.
-  Value *SrcBasePtr = SrcGEP->getOperand(0)->stripPointerCasts();
-  const SCEVUnknown *SrcBase =
-      dyn_cast<SCEVUnknown>(SE->getPointerBase(AccessFn));
-  if (!SrcBase || SrcBasePtr != SrcBase->getValue()) {
-    Subscripts.clear();
-    return false;
-  }
-
-  assert(Subscripts.size() == Sizes.size() + 1 &&
-         "Expected equal number of entries in the list of size and "
-         "subscript.");
-
-  return true;
-}
-
 namespace {
 
 void printDelinearization(raw_ostream &O, Function *F, LoopInfo *LI,