diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2344,8 +2344,12 @@
     // not create unnecessary casts if the types already match.
     Type *SelTy = A->getType();
     if (auto *VecTy = dyn_cast<VectorType>(Cond->getType())) {
+      // For a fixed or scalable vector get N from <{vscale x} N x iM>
       unsigned Elts = VecTy->getElementCount().getKnownMinValue();
-      Type *EltTy = Builder.getIntNTy(SelTy->getPrimitiveSizeInBits() / Elts);
+      // For a fixed or scalable vector, get the size in bits of N x iM; for a
+      // scalar this is just M.
+      unsigned SelEltSize = SelTy->getPrimitiveSizeInBits().getKnownMinSize();
+      Type *EltTy = Builder.getIntNTy(SelEltSize / Elts);
       SelTy = VectorType::get(EltTy, VecTy->getElementCount());
     }
     Value *BitcastC = Builder.CreateBitCast(C, SelTy);
diff --git a/llvm/test/Transforms/InstCombine/logical-select.ll b/llvm/test/Transforms/InstCombine/logical-select.ll
--- a/llvm/test/Transforms/InstCombine/logical-select.ll
+++ b/llvm/test/Transforms/InstCombine/logical-select.ll
@@ -471,6 +471,18 @@
   ret <4 x i1> %or
 }
 
+define <vscale x 1 x i1> @vec_of_bools_scalable(<vscale x 1 x i1> %a, <vscale x 1 x i1> %c, <vscale x 1 x i1> %d) {
+; CHECK-LABEL: @vec_of_bools_scalable(
+; CHECK-NEXT:    [[TMP1:%.*]] = select <vscale x 1 x i1> [[A:%.*]], <vscale x 1 x i1> [[C:%.*]], <vscale x 1 x i1> [[D:%.*]]
+; CHECK-NEXT:    ret <vscale x 1 x i1> [[TMP1]]
+;
+  %b = xor <vscale x 1 x i1> %a, shufflevector (<vscale x 1 x i1> insertelement (<vscale x 1 x i1> poison, i1 true, i32 0), <vscale x 1 x i1> poison, <vscale x 1 x i32> zeroinitializer)
+  %t11 = and <vscale x 1 x i1> %a, %c
+  %t12 = and <vscale x 1 x i1> %b, %d
+  %r = or <vscale x 1 x i1> %t11, %t12
+  ret <vscale x 1 x i1> %r
+}
+
 define i4 @vec_of_casted_bools(i4 %a, i4 %b, <4 x i1> %c) {
 ; CHECK-LABEL: @vec_of_casted_bools(
 ; CHECK-NEXT:    [[TMP1:%.*]] = bitcast i4 [[B:%.*]] to <4 x i1>
@@ -488,6 +500,25 @@
   ret i4 %or
 }
 
+define <vscale x 1 x i64> @vec_of_casted_bools_scalable(<vscale x 1 x i64> %a, <vscale x 1 x i64> %b, <vscale x 8 x i1> %cond) {
+; CHECK-LABEL: @vec_of_casted_bools_scalable(
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <vscale x 1 x i64> [[A:%.*]] to <vscale x 8 x i8>
+; CHECK-NEXT:    [[TMP2:%.*]] = bitcast <vscale x 1 x i64> [[B:%.*]] to <vscale x 8 x i8>
+; CHECK-NEXT:    [[TMP3:%.*]] = select <vscale x 8 x i1> [[COND:%.*]], <vscale x 8 x i8> [[TMP1]], <vscale x 8 x i8> [[TMP2]]
+; CHECK-NEXT:    [[TMP4:%.*]] = bitcast <vscale x 8 x i8> [[TMP3]] to <vscale x 1 x i64>
+; CHECK-NEXT:    ret <vscale x 1 x i64> [[TMP4]]
+;
+  %scond = sext <vscale x 8 x i1> %cond to <vscale x 8 x i8>
+  %notcond = xor <vscale x 8 x i1> %cond, shufflevector (<vscale x 8 x i1> insertelement (<vscale x 8 x i1> poison, i1 true, i32 0), <vscale x 8 x i1> poison, <vscale x 8 x i32> zeroinitializer)
+  %snotcond = sext <vscale x 8 x i1> %notcond to <vscale x 8 x i8>
+  %bc1 = bitcast <vscale x 8 x i8> %scond to <vscale x 1 x i64>
+  %bc2 = bitcast <vscale x 8 x i8> %snotcond to <vscale x 1 x i64>
+  %and1 = and <vscale x 1 x i64> %a, %bc1
+  %and2 = and <vscale x 1 x i64> %bc2, %b
+  %or = or <vscale x 1 x i64> %and1, %and2
+  ret <vscale x 1 x i64> %or
+}
+
 ; Inverted 'and' constants mean this is a select which is canonicalized to a shuffle.
 
 define <4 x i32> @vec_sel_consts(<4 x i32> %a, <4 x i32> %b) {