[delinearize] use SCEV exprs in getIndexExpressionsFromGEP (#162888)

clean up interface of getIndexExpressionsFromGEP to get SCEV expressions
instead of int for Sizes of the arrays.
This intends to simplify the code in #156342 by avoiding conversions
from SCEV to int and back to SCEV.

Author: sebpop

llvm/include/llvm/Analysis/Delinearization.h

@@ -154,15 +154,15 @@ bool validateDelinearizationResult(ScalarEvolution &SE,
 ///
 /// This function optimistically assumes the GEP references into a fixed size
 /// array. If this is actually true, this function returns a list of array
-/// subscript expressions in \p Subscripts and a list of integers describing
-/// the size of the individual array dimensions in \p Sizes. Both lists have
-/// either equal length or the size list is one element shorter in case there
-/// is no known size available for the outermost array dimension. Returns true
-/// if successful and false otherwise.
+/// subscript expressions in \p Subscripts and a list of SCEV expressions
+/// describing the size of the individual array dimensions in \p Sizes. Both
+/// lists have either equal length or the size list is one element shorter in
+/// case there is no known size available for the outermost array dimension.
+/// Returns true if successful and false otherwise.
 bool getIndexExpressionsFromGEP(ScalarEvolution &SE,
                                 const GetElementPtrInst *GEP,
                                 SmallVectorImpl<const SCEV *> &Subscripts,
-                                SmallVectorImpl<int> &Sizes);
+                                SmallVectorImpl<const SCEV *> &Sizes);
 
 struct DelinearizationPrinterPass
     : public PassInfoMixin<DelinearizationPrinterPass> {

llvm/lib/Analysis/Delinearization.cpp

@@ -824,12 +824,13 @@ bool llvm::validateDelinearizationResult(ScalarEvolution &SE,
 bool llvm::getIndexExpressionsFromGEP(ScalarEvolution &SE,
                                       const GetElementPtrInst *GEP,
                                       SmallVectorImpl<const SCEV *> &Subscripts,
-                                      SmallVectorImpl<int> &Sizes) {
+                                      SmallVectorImpl<const SCEV *> &Sizes) {
   assert(Subscripts.empty() && Sizes.empty() &&
          "Expected output lists to be empty on entry to this function.");
   assert(GEP && "getIndexExpressionsFromGEP called with a null GEP");
   LLVM_DEBUG(dbgs() << "\nGEP to delinearize: " << *GEP << "\n");
   Type *Ty = nullptr;
+  Type *IndexTy = SE.getEffectiveSCEVType(GEP->getPointerOperandType());
   bool DroppedFirstDim = false;
   for (unsigned i = 1; i < GEP->getNumOperands(); i++) {
     const SCEV *Expr = SE.getSCEV(GEP->getOperand(i));
@@ -855,7 +856,7 @@ bool llvm::getIndexExpressionsFromGEP(ScalarEvolution &SE,
 
     Subscripts.push_back(Expr);
     if (!(DroppedFirstDim && i == 2))
-      Sizes.push_back(ArrayTy->getNumElements());
+      Sizes.push_back(SE.getConstant(IndexTy, ArrayTy->getNumElements()));
 
     Ty = ArrayTy->getElementType();
   }

llvm/lib/Analysis/DependenceAnalysis.cpp

@@ -3265,7 +3265,7 @@ bool DependenceInfo::tryDelinearizeFixedSize(
     return false;
 
   // Check that the two size arrays are non-empty and equal in length and
-  // value.
+  // value.  SCEV expressions are uniqued, so we can compare pointers.
   if (SrcSizes.size() != DstSizes.size() ||
       !std::equal(SrcSizes.begin(), SrcSizes.end(), DstSizes.begin())) {
     SrcSubscripts.clear();

polly/lib/Analysis/ScopBuilder.cpp

@@ -1464,7 +1464,7 @@ bool ScopBuilder::buildAccessMultiDimFixed(MemAccInst Inst, ScopStmt *Stmt) {
     return false;
 
   SmallVector<const SCEV *, 4> Subscripts;
-  SmallVector<int, 4> Sizes;
+  SmallVector<const SCEV *, 4> Sizes;
   getIndexExpressionsFromGEP(SE, GEP, Subscripts, Sizes);
   auto *BasePtr = GEP->getOperand(0);
 
@@ -1476,8 +1476,6 @@ bool ScopBuilder::buildAccessMultiDimFixed(MemAccInst Inst, ScopStmt *Stmt) {
   if (BasePtr != BasePointer->getValue())
     return false;
 
-  std::vector<const SCEV *> SizesSCEV;
-
   const InvariantLoadsSetTy &ScopRIL = scop->getRequiredInvariantLoads();
 
   Loop *SurroundingLoop = Stmt->getSurroundingLoop();
@@ -1495,11 +1493,9 @@ bool ScopBuilder::buildAccessMultiDimFixed(MemAccInst Inst, ScopStmt *Stmt) {
   if (Sizes.empty())
     return false;
 
+  std::vector<const SCEV *> SizesSCEV;
   SizesSCEV.push_back(nullptr);
-
-  for (auto V : Sizes)
-    SizesSCEV.push_back(SE.getSCEV(
-        ConstantInt::get(IntegerType::getInt64Ty(BasePtr->getContext()), V)));
+  SizesSCEV.insert(SizesSCEV.end(), Sizes.begin(), Sizes.end());
 
   addArrayAccess(Stmt, Inst, AccType, BasePointer->getValue(), ElementType,
                  true, Subscripts, SizesSCEV, Val);