Index: clang/lib/CodeGen/CGLoopInfo.cpp
===================================================================
--- clang/lib/CodeGen/CGLoopInfo.cpp
+++ clang/lib/CodeGen/CGLoopInfo.cpp
@@ -268,6 +268,14 @@
     Args.push_back(MDNode::get(Ctx, Vals));
   }
 
+  // Imply vectorize.enable, but only when it is not already disabled/enabled.
+  if (Attrs.VectorizeWidth > 1 &&
+      Attrs.VectorizeEnable == LoopAttributes::Unspecified)
+    Args.push_back(
+        MDNode::get(Ctx, {MDString::get(Ctx, "llvm.loop.vectorize.enable"),
+                          ConstantAsMetadata::get(ConstantInt::get(
+                              llvm::Type::getInt1Ty(Ctx), 1))}));
+
   // Setting vectorize.width
   if (Attrs.VectorizeWidth > 0) {
     Metadata *Vals[] = {
Index: clang/test/CodeGenCXX/pragma-loop-predicate.cpp
===================================================================
--- clang/test/CodeGenCXX/pragma-loop-predicate.cpp
+++ clang/test/CodeGenCXX/pragma-loop-predicate.cpp
@@ -58,7 +58,6 @@
     List[i] = i * 2;
 }
 
-
 // CHECK:      ![[LOOP0]] = distinct !{![[LOOP0]], !3}
 // CHECK-NEXT: !3 = !{!"llvm.loop.vectorize.enable", i1 true}
 
Index: clang/test/CodeGenCXX/pragma-loop.cpp
===================================================================
--- clang/test/CodeGenCXX/pragma-loop.cpp
+++ clang/test/CodeGenCXX/pragma-loop.cpp
@@ -158,23 +158,41 @@
   for_template_constant_expression_test<double, 2, 4, 8>(List, Length);
 }
 
+void vec_width_1(int *List, int Length) {
+// CHECK-LABEL: @{{.*}}vec_width_1{{.*}}(
+// CHECK: br label {{.*}}, !llvm.loop ![[LOOP_15:.*]]
+
+  #pragma clang loop vectorize(enable) vectorize_width(1)
+  for (int i = 0; i < Length; i++)
+    List[i] = i * 2;
+}
+
+void width_1(int *List, int Length) {
+// CHECK-LABEL: @{{.*}}width_1{{.*}}(
+// CHECK: br label {{.*}}, !llvm.loop ![[LOOP_16:.*]]
+
+  #pragma clang loop vectorize_width(1)
+  for (int i = 0; i < Length; i++)
+    List[i] = i * 2;
+}
+
 // CHECK: ![[LOOP_1]] = distinct !{![[LOOP_1]], ![[UNROLL_FULL:.*]]}
 // CHECK: ![[UNROLL_FULL]] = !{!"llvm.loop.unroll.full"}
 
-// CHECK: ![[LOOP_2]] = distinct !{![[LOOP_2]], ![[UNROLL_DISABLE:.*]], ![[DISTRIBUTE_DISABLE:.*]], ![[WIDTH_8:.*]], ![[INTERLEAVE_4:.*]]}
+// CHECK: ![[LOOP_2]] = distinct !{![[LOOP_2]], ![[UNROLL_DISABLE:.*]], ![[DISTRIBUTE_DISABLE:.*]], ![[VECTORIZE_ENABLE:.*]], ![[WIDTH_8:.*]], ![[INTERLEAVE_4:.*]]}
 // CHECK: ![[UNROLL_DISABLE]] = !{!"llvm.loop.unroll.disable"}
 // CHECK: ![[DISTRIBUTE_DISABLE]] = !{!"llvm.loop.distribute.enable", i1 false}
+// CHECK: ![[VECTORIZE_ENABLE]] = !{!"llvm.loop.vectorize.enable", i1 true}
 // CHECK: ![[WIDTH_8]] = !{!"llvm.loop.vectorize.width", i32 8}
 // CHECK: ![[INTERLEAVE_4]] = !{!"llvm.loop.interleave.count", i32 4}
 
-// CHECK: ![[LOOP_3]] = distinct !{![[LOOP_3]], ![[INTERLEAVE_4:.*]], ![[INTENABLE_1:.*]], ![[FOLLOWUP_VECTOR_3:.*]]}
-// CHECK: ![[INTENABLE_1]] = !{!"llvm.loop.vectorize.enable", i1 true}
+// CHECK: ![[LOOP_3]] = distinct !{![[LOOP_3]], ![[INTERLEAVE_4:.*]], ![[VECTORIZE_ENABLE]], ![[FOLLOWUP_VECTOR_3:.*]]}
 // CHECK: ![[FOLLOWUP_VECTOR_3]] = !{!"llvm.loop.vectorize.followup_all", ![[AFTER_VECTOR_3:.*]]}
 // CHECK: ![[AFTER_VECTOR_3]] = distinct !{![[AFTER_VECTOR_3]], ![[ISVECTORIZED:.*]], ![[UNROLL_8:.*]]}
 // CHECK: ![[ISVECTORIZED]] = !{!"llvm.loop.isvectorized"}
 // CHECK: ![[UNROLL_8]] = !{!"llvm.loop.unroll.count", i32 8}
 
-// CHECK: ![[LOOP_4]] = distinct !{![[LOOP_4]], ![[WIDTH_2:.*]], ![[INTERLEAVE_2:.*]]}
+// CHECK: ![[LOOP_4]] = distinct !{![[LOOP_4]], ![[VECTORIZE_ENABLE]], ![[WIDTH_2:.*]], ![[INTERLEAVE_2:.*]]}
 // CHECK: ![[WIDTH_2]] = !{!"llvm.loop.vectorize.width", i32 2}
 // CHECK: ![[INTERLEAVE_2]] = !{!"llvm.loop.interleave.count", i32 2}
 
@@ -185,7 +203,7 @@
 // CHECK: ![[FOLLOWUP_VECTOR_6]] = !{!"llvm.loop.vectorize.followup_all", ![[AFTER_VECTOR_6:.*]]}
 // CHECK: ![[AFTER_VECTOR_6]] = distinct !{![[AFTER_VECTOR_6]], ![[ISVECTORIZED:.*]], ![[UNROLL_8:.*]]}
 
-// CHECK: ![[LOOP_7]] = distinct !{![[LOOP_7]], ![[WIDTH_5:.*]]}
+// CHECK: ![[LOOP_7]] = distinct !{![[LOOP_7]], ![[VECTORIZE_ENABLE]], ![[WIDTH_5:.*]]}
 // CHECK: ![[WIDTH_5]] = !{!"llvm.loop.vectorize.width", i32 5}
 
 // CHECK: ![[LOOP_8]] = distinct !{![[LOOP_8]], ![[WIDTH_5:.*]]}
@@ -213,5 +231,9 @@
 // CHECK: ![[AFTER_VECTOR_13]] = distinct !{![[AFTER_VECTOR_13]], ![[ISVECTORIZED:.*]], ![[UNROLL_32:.*]]}
 // CHECK: ![[UNROLL_32]] = !{!"llvm.loop.unroll.count", i32 32}
 
-// CHECK: ![[LOOP_14]] = distinct !{![[LOOP_14]], ![[WIDTH_10:.*]]}
+// CHECK: ![[LOOP_14]] = distinct !{![[LOOP_14]], ![[VECTORIZE_ENABLE]], ![[WIDTH_10:.*]]}
 // CHECK: ![[WIDTH_10]] = !{!"llvm.loop.vectorize.width", i32 10}
+
+// CHECK:      ![[LOOP_15]] = distinct !{![[LOOP_15]], ![[WIDTH_1]], ![[VECTORIZE_ENABLE]]}
+
+// CHECK-NEXT: ![[LOOP_16]] = distinct !{![[LOOP_16]], ![[WIDTH_1]]}