[LAA/SLP] Don't truncate APInt in getPointersDiff (llvm#139941)

Change getPointersDiff to return an std::optional<int64_t>, and fill
this value with using APInt::trySExtValue. This simple change requires
changes to other functions in LAA, and major changes in SLPVectorizer
changing types from 32-bit to 64-bit.

Fixes llvm#139202.

Author: artagnon

llvm/include/llvm/Analysis/LoopAccessAnalysis.h

@@ -853,11 +853,10 @@ getPtrStride(PredicatedScalarEvolution &PSE, Type *AccessTy, Value *Ptr,
 /// is a simple API that does not depend on the analysis pass.
 /// \param StrictCheck Ensure that the calculated distance matches the
 /// type-based one after all the bitcasts removal in the provided pointers.
-std::optional<int> getPointersDiff(Type *ElemTyA, Value *PtrA, Type *ElemTyB,
-                                   Value *PtrB, const DataLayout &DL,
-                                   ScalarEvolution &SE,
-                                   bool StrictCheck = false,
-                                   bool CheckType = true);
+std::optional<int64_t>
+getPointersDiff(Type *ElemTyA, Value *PtrA, Type *ElemTyB, Value *PtrB,
+                const DataLayout &DL, ScalarEvolution &SE,
+                bool StrictCheck = false, bool CheckType = true);
 
 /// Attempt to sort the pointers in \p VL and return the sorted indices
 /// in \p SortedIndices, if reordering is required.

llvm/lib/Analysis/LoopAccessAnalysis.cpp

@@ -1541,11 +1541,11 @@ llvm::getPtrStride(PredicatedScalarEvolution &PSE, Type *AccessTy, Value *Ptr,
   return std::nullopt;
 }
 
-std::optional<int> llvm::getPointersDiff(Type *ElemTyA, Value *PtrA,
-                                         Type *ElemTyB, Value *PtrB,
-                                         const DataLayout &DL,
-                                         ScalarEvolution &SE, bool StrictCheck,
-                                         bool CheckType) {
+std::optional<int64_t> llvm::getPointersDiff(Type *ElemTyA, Value *PtrA,
+                                             Type *ElemTyB, Value *PtrB,
+                                             const DataLayout &DL,
+                                             ScalarEvolution &SE,
+                                             bool StrictCheck, bool CheckType) {
   assert(PtrA && PtrB && "Expected non-nullptr pointers.");
 
   // Make sure that A and B are different pointers.
@@ -1570,7 +1570,7 @@ std::optional<int> llvm::getPointersDiff(Type *ElemTyA, Value *PtrA,
   const Value *PtrB1 = PtrB->stripAndAccumulateConstantOffsets(
       DL, OffsetB, /*AllowNonInbounds=*/true);
 
-  int Val;
+  std::optional<int64_t> Val;
   if (PtrA1 == PtrB1) {
     // Retrieve the address space again as pointer stripping now tracks through
     // `addrspacecast`.
@@ -1585,7 +1585,7 @@ std::optional<int> llvm::getPointersDiff(Type *ElemTyA, Value *PtrA,
     OffsetB = OffsetB.sextOrTrunc(IdxWidth);
 
     OffsetB -= OffsetA;
-    Val = OffsetB.getSExtValue();
+    Val = OffsetB.trySExtValue();
   } else {
     // Otherwise compute the distance with SCEV between the base pointers.
     const SCEV *PtrSCEVA = SE.getSCEV(PtrA);
@@ -1594,10 +1594,14 @@ std::optional<int> llvm::getPointersDiff(Type *ElemTyA, Value *PtrA,
         SE.computeConstantDifference(PtrSCEVB, PtrSCEVA);
     if (!Diff)
       return std::nullopt;
-    Val = Diff->getSExtValue();
+    Val = Diff->trySExtValue();
   }
-  int Size = DL.getTypeStoreSize(ElemTyA);
-  int Dist = Val / Size;
+
+  if (!Val)
+    return std::nullopt;
+
+  int64_t Size = DL.getTypeStoreSize(ElemTyA);
+  int64_t Dist = *Val / Size;
 
   // Ensure that the calculated distance matches the type-based one after all
   // the bitcasts removal in the provided pointers.
@@ -1616,14 +1620,15 @@ bool llvm::sortPtrAccesses(ArrayRef<Value *> VL, Type *ElemTy,
   // first pointer in the array.
   Value *Ptr0 = VL[0];
 
-  using DistOrdPair = std::pair<int64_t, int>;
+  using DistOrdPair = std::pair<int64_t, unsigned>;
   auto Compare = llvm::less_first();
   std::set<DistOrdPair, decltype(Compare)> Offsets(Compare);
   Offsets.emplace(0, 0);
   bool IsConsecutive = true;
   for (auto [Idx, Ptr] : drop_begin(enumerate(VL))) {
-    std::optional<int> Diff = getPointersDiff(ElemTy, Ptr0, ElemTy, Ptr, DL, SE,
-                                              /*StrictCheck=*/true);
+    std::optional<int64_t> Diff =
+        getPointersDiff(ElemTy, Ptr0, ElemTy, Ptr, DL, SE,
+                        /*StrictCheck=*/true);
     if (!Diff)
       return false;
 
@@ -1654,7 +1659,7 @@ bool llvm::isConsecutiveAccess(Value *A, Value *B, const DataLayout &DL,
     return false;
   Type *ElemTyA = getLoadStoreType(A);
   Type *ElemTyB = getLoadStoreType(B);
-  std::optional<int> Diff =
+  std::optional<int64_t> Diff =
       getPointersDiff(ElemTyA, PtrA, ElemTyB, PtrB, DL, SE,
                       /*StrictCheck=*/true, CheckType);
   return Diff && *Diff == 1;