1 files changed, 29 insertions, 21 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index a975f1c..8fe98b5 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5197,6 +5197,31 @@ bool llvm::isOverflowIntrinsicNoWrap(const WithOverflowInst *WO,
   return llvm::any_of(GuardingBranches, AllUsesGuardedByBranch);
 }
 
+/// Shifts return poison if shiftwidth is larger than the bitwidth.
+static bool shiftAmountKnownInRange(const Value *ShiftAmount) {
+  auto *C = dyn_cast<Constant>(ShiftAmount);
+  if (!C)
+    return false;
+
+  // Shifts return poison if shiftwidth is larger than the bitwidth.
+  SmallVector<const Constant *, 4> ShiftAmounts;
+  if (auto *FVTy = dyn_cast<FixedVectorType>(C->getType())) {
+    unsigned NumElts = FVTy->getNumElements();
+    for (unsigned i = 0; i < NumElts; ++i)
+      ShiftAmounts.push_back(C->getAggregateElement(i));
+  } else if (isa<ScalableVectorType>(C->getType()))
+    return false; // Can't tell, just return false to be safe
+  else
+    ShiftAmounts.push_back(C);
+
+  bool Safe = llvm::all_of(ShiftAmounts, [](const Constant *C) {
+    auto *CI = dyn_cast_or_null<ConstantInt>(C);
+    return CI && CI->getValue().ult(C->getType()->getIntegerBitWidth());
+  });
+
+  return Safe;
+}
+
 static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly,
                                    bool ConsiderFlags) {
 
@@ -5209,27 +5234,8 @@ static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly,
   switch (Opcode) {
   case Instruction::Shl:
   case Instruction::AShr:
-  case Instruction::LShr: {
-    // Shifts return poison if shiftwidth is larger than the bitwidth.
-    if (auto *C = dyn_cast<Constant>(Op->getOperand(1))) {
-      SmallVector<Constant *, 4> ShiftAmounts;
-      if (auto *FVTy = dyn_cast<FixedVectorType>(C->getType())) {
-        unsigned NumElts = FVTy->getNumElements();
-        for (unsigned i = 0; i < NumElts; ++i)
-          ShiftAmounts.push_back(C->getAggregateElement(i));
-      } else if (isa<ScalableVectorType>(C->getType()))
-        return true; // Can't tell, just return true to be safe
-      else
-        ShiftAmounts.push_back(C);
-
-      bool Safe = llvm::all_of(ShiftAmounts, [](Constant *C) {
-        auto *CI = dyn_cast_or_null<ConstantInt>(C);
-        return CI && CI->getValue().ult(C->getType()->getIntegerBitWidth());
-      });
-      return !Safe;
-    }
-    return true;
-  }
+  case Instruction::LShr:
+    return !shiftAmountKnownInRange(Op->getOperand(1));
   case Instruction::FPToSI:
   case Instruction::FPToUI:
     // fptosi/ui yields poison if the resulting value does not fit in the
@@ -5267,8 +5273,10 @@ static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly,
       case Intrinsic::uadd_sat:
       case Intrinsic::ssub_sat:
       case Intrinsic::usub_sat:
+        return false;
       case Intrinsic::sshl_sat:
       case Intrinsic::ushl_sat:
+        return !shiftAmountKnownInRange(II->getArgOperand(1));
       case Intrinsic::fma:
       case Intrinsic::fmuladd:
       case Intrinsic::sqrt: