diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
index f404e11b9c0f0..e22b04e1bb0b3 100644
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -448,7 +448,7 @@ bool CallBase::paramHasNonNullAttr(unsigned ArgNo,
       (AllowUndefOrPoison || paramHasAttr(ArgNo, Attribute::NoUndef)))
     return true;
 
-  if (getParamDereferenceableBytes(ArgNo) > 0 &&
+  if (paramHasAttr(ArgNo, Attribute::Dereferenceable) &&
       !NullPointerIsDefined(
           getCaller(),
           getArgOperand(ArgNo)->getType()->getPointerAddressSpace()))
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 7840601d341b8..b7299e01b0c5f 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -8224,8 +8224,8 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I, bool PtrValu
       if (CB->isArgOperand(&Use)) {
         unsigned ArgIdx = CB->getArgOperandNo(&Use);
         // Passing null to a nonnnull+noundef argument is undefined.
-        if (C->isNullValue() && CB->isPassingUndefUB(ArgIdx) &&
-            CB->paramHasAttr(ArgIdx, Attribute::NonNull))
+        if (isa<ConstantPointerNull>(C) &&
+            CB->paramHasNonNullAttr(ArgIdx, /*AllowUndefOrPoison=*/false))
           return !PtrValueMayBeModified;
         // Passing undef to a noundef argument is undefined.
         if (isa<UndefValue>(C) && CB->isPassingUndefUB(ArgIdx))
diff --git a/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll b/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
index aae1ab032f36e..2da5d18b63f49 100644
--- a/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
+++ b/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
@@ -238,7 +238,7 @@ else:
 }
 
 declare ptr @fn_nonnull_noundef_arg(ptr nonnull noundef %p)
-declare ptr @fn_nonnull_deref_arg(ptr nonnull dereferenceable(4) %p)
+declare ptr @fn_deref_arg(ptr dereferenceable(4) %p)
 declare ptr @fn_nonnull_deref_or_null_arg(ptr nonnull dereferenceable_or_null(4) %p)
 declare ptr @fn_nonnull_arg(ptr nonnull %p)
 declare ptr @fn_noundef_arg(ptr noundef %p)
@@ -271,7 +271,7 @@ define void @test9_deref(i1 %X, ptr %Y) {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[TMP0:%.*]] = xor i1 [[X:%.*]], true
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[TMP0]])
-; CHECK-NEXT:    [[TMP1:%.*]] = call ptr @fn_nonnull_deref_arg(ptr [[Y:%.*]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call ptr @fn_deref_arg(ptr [[Y:%.*]])
 ; CHECK-NEXT:    ret void
 ;
 entry:
@@ -282,7 +282,7 @@ if:
 
 else:
   %phi = phi ptr [ %Y, %entry ], [ null, %if ]
-  call ptr @fn_nonnull_deref_arg(ptr %phi)
+  call ptr @fn_deref_arg(ptr %phi)
   ret void
 }
 
@@ -290,9 +290,8 @@ else:
 define void @test9_deref_or_null(i1 %X, ptr %Y) {
 ; CHECK-LABEL: @test9_deref_or_null(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[TMP0:%.*]] = xor i1 [[X:%.*]], true
-; CHECK-NEXT:    call void @llvm.assume(i1 [[TMP0]])
-; CHECK-NEXT:    [[TMP1:%.*]] = call ptr @fn_nonnull_deref_or_null_arg(ptr [[Y:%.*]])
+; CHECK-NEXT:    [[Y:%.*]] = select i1 [[X:%.*]], ptr null, ptr [[Y1:%.*]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call ptr @fn_nonnull_deref_or_null_arg(ptr [[Y]])
 ; CHECK-NEXT:    ret void
 ;
 entry: