Index: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
@@ -27793,6 +27793,8 @@
   if (InScalarVT.getSizeInBits() <= ScalarVT.getSizeInBits())
     return SDValue();
 
+  if (!Subtarget.hasSSE2())
+    return SDValue();
   if (Subtarget.hasAVX512()) {
     if (VT.getSizeInBits() > 512)
       return SDValue();
Index: llvm/trunk/test/CodeGen/X86/no-sse2-avg.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/no-sse2-avg.ll
+++ llvm/trunk/test/CodeGen/X86/no-sse2-avg.ll
@@ -0,0 +1,32 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; REQUIRES: asserts
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=-sse2 | FileCheck %s
+
+define <16 x i8> @PR27973() {
+; CHECK-LABEL: PR27973:
+; CHECK:       # BB#0:
+; CHECK-NEXT:    movb $0, 15(%rdi)
+; CHECK-NEXT:    movb $0, 14(%rdi)
+; CHECK-NEXT:    movb $0, 13(%rdi)
+; CHECK-NEXT:    movb $0, 12(%rdi)
+; CHECK-NEXT:    movb $0, 11(%rdi)
+; CHECK-NEXT:    movb $0, 10(%rdi)
+; CHECK-NEXT:    movb $0, 9(%rdi)
+; CHECK-NEXT:    movb $0, 8(%rdi)
+; CHECK-NEXT:    movb $0, 7(%rdi)
+; CHECK-NEXT:    movb $0, 6(%rdi)
+; CHECK-NEXT:    movb $0, 5(%rdi)
+; CHECK-NEXT:    movb $0, 4(%rdi)
+; CHECK-NEXT:    movb $0, 3(%rdi)
+; CHECK-NEXT:    movb $0, 2(%rdi)
+; CHECK-NEXT:    movb $0, 1(%rdi)
+; CHECK-NEXT:    movb $0, (%rdi)
+; CHECK-NEXT:    movq %rdi, %rax
+; CHECK-NEXT:    retq
+;
+  %t0 = zext <16 x i8> zeroinitializer to <16 x i32>
+  %t1 = add nuw nsw <16 x i32> %t0, <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
+  %t2 = lshr <16 x i32> %t1, <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
+  %t3 = trunc <16 x i32> %t2 to <16 x i8>
+  ret <16 x i8> %t3
+}