[SCEV] SCEVPtrToIntExpr simplifications

If we've got an SCEVPtrToIntExpr(op), where op is not an SCEVUnknown,
we want to sink the SCEVPtrToIntExpr into an operand,
so that the operation is performed on integers,
and eventually we end up with just an `SCEVPtrToIntExpr(SCEVUnknown)`.

Reviewed By: mkazantsev

Differential Revision: https://reviews.llvm.org/D89692

Author: LebedevRI

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -1047,17 +1047,61 @@ const SCEV *ScalarEvolution::getPtrToIntExpr(const SCEV *Op, Type *Ty,
   ID.AddPointer(Op);
   void *IP = nullptr;
   if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP))
-    return getTruncateOrZeroExtend(S, Ty);
+    return getTruncateOrZeroExtend(S, Ty, Depth);
 
-  assert(!isa<SCEVConstant>(Op) &&
-         "SCEVConstant is an integer, no constant folding to do.");
+  assert((isa<SCEVNAryExpr>(Op) || isa<SCEVUnknown>(Op)) &&
+         "We can only gen an nary expression, or an unknown here.");
 
-  // FIXME: simplifications.
+  Type *IntPtrTy = getDataLayout().getIntPtrType(Op->getType());
+
+  // If the input operand is not an unknown (and thus is an nary expression),
+  // sink the cast to operands, so that the operation is performed on integers,
+  // and we eventually end up with just an ptrtoint(unknown).
+  if (const SCEVNAryExpr *NaryExpr = dyn_cast<SCEVNAryExpr>(Op)) {
+    SmallVector<const SCEV *, 2> NewOps;
+    NewOps.reserve(NaryExpr->getNumOperands());
+    for (const SCEV *Op : NaryExpr->operands())
+      NewOps.push_back(Op->getType()->isPointerTy()
+                           ? getPtrToIntExpr(Op, IntPtrTy, Depth + 1)
+                           : Op);
+    const SCEV *NewNaryExpr = nullptr;
+    switch (SCEVTypes SCEVType = NaryExpr->getSCEVType()) {
+    case scAddExpr:
+      NewNaryExpr = getAddExpr(NewOps, NaryExpr->getNoWrapFlags(), Depth + 1);
+      break;
+    case scAddRecExpr:
+      NewNaryExpr =
+          getAddRecExpr(NewOps, cast<SCEVAddRecExpr>(NaryExpr)->getLoop(),
+                        NaryExpr->getNoWrapFlags());
+      break;
+    case scUMaxExpr:
+    case scSMaxExpr:
+    case scUMinExpr:
+    case scSMinExpr:
+      NewNaryExpr = getMinMaxExpr(SCEVType, NewOps);
+      break;
+
+    case scMulExpr:
+      NewNaryExpr = getMulExpr(NewOps, NaryExpr->getNoWrapFlags(), Depth + 1);
+      break;
+    case scUDivExpr:
+      NewNaryExpr = getUDivExpr(NewOps[0], NewOps[1]);
+      break;
+    case scConstant:
+    case scTruncate:
+    case scZeroExtend:
+    case scSignExtend:
+    case scPtrToInt:
+    case scUnknown:
+    case scCouldNotCompute:
+      llvm_unreachable("We can't get these types here.");
+    }
+    return getTruncateOrZeroExtend(NewNaryExpr, Ty, Depth);
+  }
 
   // The cast wasn't folded; create an explicit cast node. We can reuse
   // the existing insert position since if we get here, we won't have
   // made any changes which would invalidate it.
-  Type *IntPtrTy = getDataLayout().getIntPtrType(Op->getType());
   assert(getDataLayout().getTypeSizeInBits(getEffectiveSCEVType(
              Op->getType())) == getDataLayout().getTypeSizeInBits(IntPtrTy) &&
          "We can only model ptrtoint if SCEV's effective (integer) type is "
@@ -1066,7 +1110,7 @@ const SCEV *ScalarEvolution::getPtrToIntExpr(const SCEV *Op, Type *Ty,
       SCEVPtrToIntExpr(ID.Intern(SCEVAllocator), Op, IntPtrTy);
   UniqueSCEVs.InsertNode(S, IP);
   addToLoopUseLists(S);
-  return getTruncateOrZeroExtend(S, Ty);
+  return getTruncateOrZeroExtend(S, Ty, Depth);
 }
 
 const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op, Type *Ty,