[NFC] Promote willNotOverflow() / getStrengthenedNoWrapFlagsFromBinOp() from IndVars into SCEV proper

We might want to use it when creating SCEV proper in createSCEV(),
now that we don't `forgetValue()` in `SimplifyIndvar::strengthenOverflowingOperation()`,
which might have caused us to loose some optimization potential.

1 files changed, 21 insertions, 69 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 246bc0a..ff60667 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -422,46 +422,10 @@ void SimplifyIndvar::simplifyIVRemainder(BinaryOperator *Rem, Value *IVOperand,
   replaceSRemWithURem(Rem);
 }
 
-static bool willNotOverflow(ScalarEvolution *SE, Instruction::BinaryOps BinOp,
-                            bool Signed, const SCEV *LHS, const SCEV *RHS) {
-  const SCEV *(ScalarEvolution::*Operation)(const SCEV *, const SCEV *,
-                                            SCEV::NoWrapFlags, unsigned);
-  switch (BinOp) {
-  default:
-    llvm_unreachable("Unsupported binary op");
-  case Instruction::Add:
-    Operation = &ScalarEvolution::getAddExpr;
-    break;
-  case Instruction::Sub:
-    Operation = &ScalarEvolution::getMinusSCEV;
-    break;
-  case Instruction::Mul:
-    Operation = &ScalarEvolution::getMulExpr;
-    break;
-  }
-
-  const SCEV *(ScalarEvolution::*Extension)(const SCEV *, Type *, unsigned) =
-      Signed ? &ScalarEvolution::getSignExtendExpr
-             : &ScalarEvolution::getZeroExtendExpr;
-
-  // Check ext(LHS op RHS) == ext(LHS) op ext(RHS)
-  auto *NarrowTy = cast<IntegerType>(LHS->getType());
-  auto *WideTy =
-    IntegerType::get(NarrowTy->getContext(), NarrowTy->getBitWidth() * 2);
-
-  const SCEV *A =
-      (SE->*Extension)((SE->*Operation)(LHS, RHS, SCEV::FlagAnyWrap, 0),
-                       WideTy, 0);
-  const SCEV *B =
-      (SE->*Operation)((SE->*Extension)(LHS, WideTy, 0),
-                       (SE->*Extension)(RHS, WideTy, 0), SCEV::FlagAnyWrap, 0);
-  return A == B;
-}
-
 bool SimplifyIndvar::eliminateOverflowIntrinsic(WithOverflowInst *WO) {
   const SCEV *LHS = SE->getSCEV(WO->getLHS());
   const SCEV *RHS = SE->getSCEV(WO->getRHS());
-  if (!willNotOverflow(SE, WO->getBinaryOp(), WO->isSigned(), LHS, RHS))
+  if (!SE->willNotOverflow(WO->getBinaryOp(), WO->isSigned(), LHS, RHS))
     return false;
 
   // Proved no overflow, nuke the overflow check and, if possible, the overflow
@@ -502,7 +466,7 @@ bool SimplifyIndvar::eliminateOverflowIntrinsic(WithOverflowInst *WO) {
 bool SimplifyIndvar::eliminateSaturatingIntrinsic(SaturatingInst *SI) {
   const SCEV *LHS = SE->getSCEV(SI->getLHS());
   const SCEV *RHS = SE->getSCEV(SI->getRHS());
-  if (!willNotOverflow(SE, SI->getBinaryOp(), SI->isSigned(), LHS, RHS))
+  if (!SE->willNotOverflow(SI->getBinaryOp(), SI->isSigned(), LHS, RHS))
     return false;
 
   BinaryOperator *BO = BinaryOperator::Create(
@@ -756,37 +720,25 @@ bool SimplifyIndvar::eliminateIdentitySCEV(Instruction *UseInst,
 /// unsigned-overflow.  Returns true if anything changed, false otherwise.
 bool SimplifyIndvar::strengthenOverflowingOperation(BinaryOperator *BO,
                                                     Value *IVOperand) {
-  // Fastpath: we don't have any work to do if `BO` is `nuw` and `nsw`.
-  if (BO->hasNoUnsignedWrap() && BO->hasNoSignedWrap())
-    return false;
-
-  if (BO->getOpcode() != Instruction::Add &&
-      BO->getOpcode() != Instruction::Sub &&
-      BO->getOpcode() != Instruction::Mul)
-    return false;
-
-  const SCEV *LHS = SE->getSCEV(BO->getOperand(0));
-  const SCEV *RHS = SE->getSCEV(BO->getOperand(1));
-  bool Changed = false;
-
-  if (!BO->hasNoUnsignedWrap() &&
-      willNotOverflow(SE, BO->getOpcode(), /* Signed */ false, LHS, RHS)) {
-    BO->setHasNoUnsignedWrap();
-    Changed = true;
-  }
-
-  if (!BO->hasNoSignedWrap() &&
-      willNotOverflow(SE, BO->getOpcode(), /* Signed */ true, LHS, RHS)) {
-    BO->setHasNoSignedWrap();
-    Changed = true;
-  }
-
-  // The willNotOverflow() check might infer additional nowrap flags on addrecs
-  // while performing zero/sign extensions. We could call forgetValue() here
-  // to make sure those flags also propagate to any other SCEV expressions
-  // based on the addrec. However, this can have pathological compile-time
-  // impact, see https://bugs.llvm.org/show_bug.cgi?id=50384.
-  return Changed;
+  SCEV::NoWrapFlags Flags;
+  bool Deduced;
+  std::tie(Flags, Deduced) = SE->getStrengthenedNoWrapFlagsFromBinOp(
+      cast<OverflowingBinaryOperator>(BO));
+
+  if (!Deduced)
+    return Deduced;
+
+  BO->setHasNoUnsignedWrap(ScalarEvolution::maskFlags(Flags, SCEV::FlagNUW) ==
+                           SCEV::FlagNUW);
+  BO->setHasNoSignedWrap(ScalarEvolution::maskFlags(Flags, SCEV::FlagNSW) ==
+                         SCEV::FlagNSW);
+
+  // The getStrengthenedNoWrapFlagsFromBinOp() check inferred additional nowrap
+  // flags on addrecs while performing zero/sign extensions. We could call
+  // forgetValue() here to make sure those flags also propagate to any other
+  // SCEV expressions based on the addrec. However, this can have pathological
+  // compile-time impact, see https://bugs.llvm.org/show_bug.cgi?id=50384.
+  return Deduced;
 }
 
 /// Annotate the Shr in (X << IVOperand) >> C as exact using the