Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -18256,6 +18256,18 @@
     return DAG.getNode(X86ISD::SELECTS, DL, VT, Cmp, Op1, Op2);
   }
 
+  // For v64i1 without 64-bit support we need to split and rejoin.
+  if (VT == MVT::v64i1 && !Subtarget.is64Bit()) {
+    assert(Subtarget.hasBWI() && "Expected BWI to be legal");
+    SDValue Op1Lo = extractSubVector(Op1, 0, DAG, DL, 32);
+    SDValue Op2Lo = extractSubVector(Op2, 0, DAG, DL, 32);
+    SDValue Op1Hi = extractSubVector(Op1, 32, DAG, DL, 32);
+    SDValue Op2Hi = extractSubVector(Op2, 32, DAG, DL, 32);
+    SDValue Lo = DAG.getSelect(DL, MVT::v32i1, Cond, Op1Lo, Op2Lo);
+    SDValue Hi = DAG.getSelect(DL, MVT::v32i1, Cond, Op1Hi, Op2Hi);
+    return DAG.getNode(ISD::CONCAT_VECTORS, DL, VT, Lo, Hi);
+  }
+
   if (VT.isVector() && VT.getVectorElementType() == MVT::i1) {
     SDValue Op1Scalar;
     if (ISD::isBuildVectorOfConstantSDNodes(Op1.getNode()))
Index: test/CodeGen/X86/pr35972.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/pr35972.ll
@@ -0,0 +1,20 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=i686-unknown-linux-gnu %s -o - -mattr=avx512bw | FileCheck %s
+
+define void @test3(i32 %c, <64 x i1>* %ptr) {
+; CHECK-LABEL: test3:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; CHECK-NEXT:    cmpl $1, {{[0-9]+}}(%esp)
+; CHECK-NEXT:    sbbl %ecx, %ecx
+; CHECK-NEXT:    kmovd %ecx, %k0
+; CHECK-NEXT:    kunpckdq %k0, %k0, %k0
+; CHECK-NEXT:    kmovq %k0, (%eax)
+; CHECK-NEXT:    retl
+  %cmp = icmp eq i32 %c, 0
+  %insert = insertelement <64 x i1> undef, i1 %cmp, i32 0
+  %shuf = shufflevector <64 x i1> %insert, <64 x i1> undef, <64 x i32> zeroinitializer
+  store <64 x i1> %shuf, <64 x i1>* %ptr
+  ret void
+}
+