diff --git a/llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h b/llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h
--- a/llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h
+++ b/llvm/include/llvm/Transforms/Vectorize/LoopVectorizationLegality.h
@@ -96,6 +96,20 @@
     FK_Enabled = 1,    ///< Forcing enabled.
   };
 
+  enum ScalableForceKind {
+    /// Not selected.
+    SK_Unspecified = -1,
+    /// Disables vectorization with scalable vectors.
+    SK_FixedWidthOnly = 0,
+    /// Vectorize loops using scalable vectors or fixed-width vectors, but favor
+    /// scalable vectors when the cost-model is inconclusive. This is the
+    /// default when the scalable.enable hint is enabled through a pragma.
+    SK_PreferScalable = 1,
+    /// Vectorize loops using scalable vectors or fixed-width  vectors, but
+    /// favor fixed-width vectors when the cost is inconclusive.
+    SK_PreferFixedWidth = 2,
+  };
+
   LoopVectorizeHints(const Loop *L, bool InterleaveOnlyWhenForced,
                      OptimizationRemarkEmitter &ORE);
 
@@ -109,7 +123,8 @@
   void emitRemarkWithHints() const;
 
   ElementCount getWidth() const {
-    return ElementCount::get(Width.Value, isScalable());
+    return ElementCount::get(Width.Value,
+                             isScalableVectorizationExplicitlyEnabled());
   }
   unsigned getInterleave() const {
     if (Interleave.Value)
@@ -129,7 +144,16 @@
     return (ForceKind)Force.Value;
   }
 
-  bool isScalable() const { return Scalable.Value; }
+  /// \return true if scalable vectorization has been explicitly enabled.
+  bool isScalableVectorizationExplicitlyEnabled() const {
+    return (ScalableForceKind)Scalable.Value == SK_PreferFixedWidth ||
+           (ScalableForceKind)Scalable.Value == SK_PreferScalable;
+  }
+
+  /// \return true if scalable vectorization has been explicitly disabled.
+  bool isScalableVectorizationDisabled() const {
+    return Scalable.Value == SK_FixedWidthOnly;
+  }
 
   /// If hints are provided that force vectorization, use the AlwaysPrint
   /// pass name to force the frontend to print the diagnostic.
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -48,6 +48,23 @@
     cl::desc("The maximum number of SCEV checks allowed with a "
              "vectorize(enable) pragma"));
 
+// FIXME: When scalable vectorization is stable enough, change the default
+// to SK_PreferFixedWidth.
+static cl::opt<LoopVectorizeHints::ScalableForceKind> ScalableVectorization(
+    "scalable-vectorization", cl::init(LoopVectorizeHints::SK_FixedWidthOnly),
+    cl::Hidden,
+    cl::desc("Control whether the compiler can use scalable vectors to "
+             "vectorize a loop"),
+    cl::values(
+        clEnumValN(LoopVectorizeHints::SK_FixedWidthOnly, "off",
+                   "Scalable vectorisation is disabled."),
+        clEnumValN(LoopVectorizeHints::SK_PreferFixedWidth, "on",
+                   "Scalable vectorisation is available, but favor fixed-width "
+                   "vectorisation when the cost is inconclusive."),
+        clEnumValN(LoopVectorizeHints::SK_PreferScalable, "preferred",
+                   "Scalable vectorisation is available and favored when the "
+                   "cost is inconclusive.")));
+
 /// Maximum vectorization interleave count.
 static const unsigned MaxInterleaveFactor = 16;
 
@@ -77,8 +94,8 @@
       Force("vectorize.enable", FK_Undefined, HK_FORCE),
       IsVectorized("isvectorized", 0, HK_ISVECTORIZED),
       Predicate("vectorize.predicate.enable", FK_Undefined, HK_PREDICATE),
-      Scalable("vectorize.scalable.enable", false, HK_SCALABLE), TheLoop(L),
-      ORE(ORE) {
+      Scalable("vectorize.scalable.enable", SK_Unspecified, HK_SCALABLE),
+      TheLoop(L), ORE(ORE) {
   // Populate values with existing loop metadata.
   getHintsFromMetadata();
 
@@ -86,6 +103,16 @@
   if (VectorizerParams::isInterleaveForced())
     Interleave.Value = VectorizerParams::VectorizationInterleave;
 
+  if (Scalable.Value == SK_Unspecified)
+    // If the width is set, but the metadata says nothing about the scalable
+    // property, then assume it concerns only a fixed-width UserVF.
+    // If width is not set, the flag takes precedence.
+    Scalable.Value = Width.Value ? SK_FixedWidthOnly : ScalableVectorization;
+  else if (ScalableVectorization == SK_FixedWidthOnly)
+    // If the flag is set to disable any use of scalable vectors, override the
+    // loop hint.
+    Scalable.Value = SK_FixedWidthOnly;
+
   if (IsVectorized.Value != 1)
     // If the vectorization width and interleaving count are both 1 then
     // consider the loop to have been already vectorized because there's
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -5657,6 +5657,12 @@
     return ElementCount::getScalable(0);
   }
 
+  if (Hints->isScalableVectorizationDisabled()) {
+    reportVectorizationInfo("Scalable vectorization is explicitly disabled",
+                            "ScalableVectorizationDisabled", ORE, TheLoop);
+    return ElementCount::getScalable(0);
+  }
+
   auto MaxScalableVF = ElementCount::getScalable(
       std::numeric_limits<ElementCount::ScalarTy>::max());
 
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll b/llvm/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/first-order-recurrence.ll
@@ -1,5 +1,5 @@
-; RUN: opt -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S < %s | FileCheck %s --check-prefix=CHECK-VF4UF1
-; RUN: opt -loop-vectorize -force-vector-width=4 -force-vector-interleave=2 -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S < %s | FileCheck %s --check-prefix=CHECK-VF4UF2
+; RUN: opt -loop-vectorize -scalable-vectorization=on -force-vector-width=4 -force-vector-interleave=1 -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S < %s | FileCheck %s --check-prefix=CHECK-VF4UF1
+; RUN: opt -loop-vectorize -scalable-vectorization=on -force-vector-width=4 -force-vector-interleave=2 -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S < %s | FileCheck %s --check-prefix=CHECK-VF4UF2
 
 ; We vectorize this first order recurrence, with a set of insertelements for
 ; each unrolled part. Make sure these insertelements are generated in-order,
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/masked-op-cost.ll b/llvm/test/Transforms/LoopVectorize/AArch64/masked-op-cost.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/masked-op-cost.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/masked-op-cost.ll
@@ -1,5 +1,5 @@
 ; REQUIRES: asserts
-; RUN: opt -loop-vectorize -force-vector-interleave=1 -S -debug < %s 2>%t | FileCheck %s
+; RUN: opt -loop-vectorize -scalable-vectorization=on -force-vector-interleave=1 -S -debug-only=loop-vectorize < %s 2>%t | FileCheck %s
 ; RUN: cat %t | FileCheck %s --check-prefix=CHECK-COST
 
 target triple = "aarch64-unknown-linux-gnu"
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-call.ll b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-call.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-call.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-call.ll
@@ -1,4 +1,4 @@
-; RUN: opt -S -loop-vectorize -force-vector-interleave=1 -instcombine -mattr=+sve -mtriple aarch64-unknown-linux-gnu < %s | FileCheck %s
+; RUN: opt -S -loop-vectorize -force-vector-interleave=1 -instcombine -mattr=+sve -mtriple aarch64-unknown-linux-gnu -scalable-vectorization=on < %s | FileCheck %s
 
 define void @vec_load(i64 %N, double* nocapture %a, double* nocapture readonly %b) {
 ; CHECK-LABEL: @vec_load
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-reductions.ll b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-reductions.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-reductions.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-reductions.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -loop-vectorize -pass-remarks=loop-vectorize -pass-remarks-analysis=loop-vectorize -pass-remarks-missed=loop-vectorize -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S 2>%t | FileCheck %s -check-prefix=CHECK
+; RUN: opt < %s -loop-vectorize -pass-remarks=loop-vectorize -pass-remarks-analysis=loop-vectorize -pass-remarks-missed=loop-vectorize -mtriple aarch64-unknown-linux-gnu -mattr=+sve -S -scalable-vectorization=on 2>%t | FileCheck %s -check-prefix=CHECK
 ; RUN: cat %t | FileCheck %s -check-prefix=CHECK-REMARK
 
 ; Reduction can be vectorized
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-strict-fadd.ll b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-strict-fadd.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-strict-fadd.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-strict-fadd.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -loop-vectorize -mtriple aarch64-unknown-linux-gnu -mattr=+sve -enable-strict-reductions -S | FileCheck %s -check-prefix=CHECK
+; RUN: opt < %s -loop-vectorize -scalable-vectorization=on -mtriple aarch64-unknown-linux-gnu -mattr=+sve -enable-strict-reductions -S | FileCheck %s -check-prefix=CHECK
 
 define float @fadd_strict(float* noalias nocapture readonly %a, i64 %n) {
 ; CHECK-LABEL: @fadd_strict
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-analysis.ll b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-analysis.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-analysis.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-analysis.ll
@@ -1,6 +1,8 @@
 ; REQUIRES: asserts
-; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -force-target-instruction-cost=1 -loop-vectorize -S -debug-only=loop-vectorize < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK_SCALABLE_ON
-; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -force-target-instruction-cost=1 -loop-vectorize -S -debug-only=loop-vectorize -vectorizer-maximize-bandwidth < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK_SCALABLE_ON_MAXBW
+; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -force-target-instruction-cost=1 -loop-vectorize -S -debug-only=loop-vectorize -scalable-vectorization=on        < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK_SCALABLE_ON
+; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -force-target-instruction-cost=1 -loop-vectorize -S -debug-only=loop-vectorize -scalable-vectorization=preferred < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK_SCALABLE_PREFERRED
+; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -force-target-instruction-cost=1 -loop-vectorize -S -debug-only=loop-vectorize -scalable-vectorization=off       < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK_SCALABLE_DISABLED
+; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -force-target-instruction-cost=1 -loop-vectorize -S -debug-only=loop-vectorize -vectorizer-maximize-bandwidth -scalable-vectorization=on < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK_SCALABLE_ON_MAXBW
 
 ; Test that the MaxVF for the following loop, that has no dependence distances,
 ; is calculated as vscale x 4 (max legal SVE vector size) or vscale x 16
@@ -8,6 +10,8 @@
 define void @test0(i32* %a, i8* %b, i32* %c) {
 ; CHECK: LV: Checking a loop in "test0"
 ; CHECK_SCALABLE_ON: LV: Found feasible scalable VF = vscale x 4
+; CHECK_SCALABLE_PREFERRED: LV: Found feasible scalable VF = vscale x 4
+; CHECK_SCALABLE_DISABLED-NOT: LV: Found feasible scalable VF
 ; CHECK_SCALABLE_ON_MAXBW: LV: Found feasible scalable VF = vscale x 16
 entry:
   br label %loop
@@ -35,6 +39,8 @@
 define void @test1(i32* %a, i8* %b) {
 ; CHECK: LV: Checking a loop in "test1"
 ; CHECK_SCALABLE_ON: LV: Found feasible scalable VF = vscale x 4
+; CHECK_SCALABLE_PREFERRED: LV: Found feasible scalable VF = vscale x 4
+; CHECK_SCALABLE_DISABLED-NOT: LV: Found feasible scalable VF
 ; CHECK_SCALABLE_ON_MAXBW: LV: Found feasible scalable VF = vscale x 4
 entry:
   br label %loop
@@ -63,6 +69,8 @@
 define void @test2(i32* %a, i8* %b) {
 ; CHECK: LV: Checking a loop in "test2"
 ; CHECK_SCALABLE_ON: LV: Found feasible scalable VF = vscale x 2
+; CHECK_SCALABLE_PREFERRED: LV: Found feasible scalable VF = vscale x 2
+; CHECK_SCALABLE_DISABLED-NOT: LV: Found feasible scalable VF
 ; CHECK_SCALABLE_ON_MAXBW: LV: Found feasible scalable VF = vscale x 2
 entry:
   br label %loop
@@ -91,6 +99,8 @@
 define void @test3(i32* %a, i8* %b) {
 ; CHECK: LV: Checking a loop in "test3"
 ; CHECK_SCALABLE_ON: LV: Found feasible scalable VF = vscale x 1
+; CHECK_SCALABLE_PREFERRED: LV: Found feasible scalable VF = vscale x 1
+; CHECK_SCALABLE_DISABLED-NOT: LV: Found feasible scalable VF
 ; CHECK_SCALABLE_ON_MAXBW: LV: Found feasible scalable VF = vscale x 1
 entry:
   br label %loop
@@ -120,6 +130,8 @@
 define void @test4(i32* %a, i32* %b) {
 ; CHECK: LV: Checking a loop in "test4"
 ; CHECK_SCALABLE_ON-NOT: LV: Found feasible scalable VF
+; CHECK_SCALABLE_PREFERRED-NOT: LV: Found feasible scalable VF
+; CHECK_SCALABLE_DISABLED-NOT: LV: Found feasible scalable VF
 ; CHECK_SCALABLE_ON_MAXBW-NOT: LV: Found feasible scalable VF
 entry:
   br label %loop
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-hint.ll b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-hint.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-hint.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-hint.ll
@@ -1,8 +1,8 @@
 ; REQUIRES: asserts
-; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -loop-vectorize -S < %s 2>&1 | FileCheck %s
-; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -loop-vectorize -pass-remarks-analysis=loop-vectorize -debug-only=loop-vectorize -S < %s 2>&1 | FileCheck --check-prefix=CHECK-DBG %s
-; RUN: opt -mtriple=aarch64-none-linux-gnu -loop-vectorize -pass-remarks-analysis=loop-vectorize -debug-only=loop-vectorize -S < %s 2>&1 | FileCheck --check-prefix=CHECK-NO-SVE %s
-; RUN: opt -mtriple=aarch64-none-linux-gnu -loop-vectorize -force-target-supports-scalable-vectors=true -pass-remarks-analysis=loop-vectorize -debug-only=loop-vectorize -S < %s 2>&1 | FileCheck --check-prefix=CHECK-NO-MAX-VSCALE %s
+; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -loop-vectorize -S -scalable-vectorization=on < %s 2>&1 | FileCheck %s
+; RUN: opt -mtriple=aarch64-none-linux-gnu -mattr=+sve -loop-vectorize -pass-remarks-analysis=loop-vectorize -debug-only=loop-vectorize -S -scalable-vectorization=on < %s 2>&1 | FileCheck --check-prefix=CHECK-DBG %s
+; RUN: opt -mtriple=aarch64-none-linux-gnu -loop-vectorize -pass-remarks-analysis=loop-vectorize -debug-only=loop-vectorize -S -scalable-vectorization=on < %s 2>&1 | FileCheck --check-prefix=CHECK-NO-SVE %s
+; RUN: opt -mtriple=aarch64-none-linux-gnu -loop-vectorize -force-target-supports-scalable-vectors=true -pass-remarks-analysis=loop-vectorize -debug-only=loop-vectorize -S -scalable-vectorization=on < %s 2>&1 | FileCheck --check-prefix=CHECK-NO-MAX-VSCALE %s
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-basic-vec.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-basic-vec.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-basic-vec.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-basic-vec.ll
@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -mattr=+sve < %s -S | FileCheck %s
+; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -mattr=+sve -scalable-vectorization=on < %s -S | FileCheck %s
 
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-cond-inv-loads.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-cond-inv-loads.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-cond-inv-loads.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-cond-inv-loads.ll
@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -mattr=+sve -S %s -o - | FileCheck %s
+; RUN: opt -loop-vectorize -scalable-vectorization=on -dce -instcombine -mtriple aarch64-linux-gnu -mattr=+sve -S %s -o - | FileCheck %s
 
 define void @cond_inv_load_i32i32i16(i32* noalias nocapture %a, i32* noalias nocapture readonly %cond, i16* noalias nocapture readonly %inv, i64 %n) {
 ; CHECK-LABEL: @cond_inv_load_i32i32i16
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-extract-last-veclane.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-extract-last-veclane.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-extract-last-veclane.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-extract-last-veclane.ll
@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -S < %s | FileCheck %s
+; RUN: opt -loop-vectorize -scalable-vectorization=on -dce -instcombine -mtriple aarch64-linux-gnu -S < %s | FileCheck %s
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 target triple = "aarch64-unknown-linux-gnu"
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-gather-scatter.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-gather-scatter.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-gather-scatter.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-gather-scatter.ll
@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -mattr=+sve -S %s -o - | FileCheck %s
+; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -mattr=+sve -S %s -scalable-vectorization=on -o - | FileCheck %s
 
 define void @gather_nxv4i32_ind64(float* noalias nocapture readonly %a, i64* noalias nocapture readonly %b, float* noalias nocapture %c, i64 %n) {
 ; CHECK-LABEL: @gather_nxv4i32_ind64
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-inductions.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-inductions.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-inductions.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-inductions.ll
@@ -1,4 +1,4 @@
-; RUN: opt -mtriple aarch64-linux-gnu -mattr=+sve -loop-vectorize -dce -instcombine < %s -S | FileCheck %s
+; RUN: opt -mtriple aarch64-linux-gnu -mattr=+sve -loop-vectorize -scalable-vectorization=on -dce -instcombine < %s -S | FileCheck %s
 
 ; Test that we can add on the induction variable
 ;   for (long long i = 0; i < n; i++) {
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-inv-loads.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-inv-loads.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-inv-loads.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-inv-loads.ll
@@ -1,4 +1,4 @@
-; RUN: opt -S -loop-vectorize -mattr=+sve -mtriple aarch64-linux-gnu < %s | FileCheck %s
+; RUN: opt -S -loop-vectorize -scalable-vectorization=on -mattr=+sve -mtriple aarch64-linux-gnu < %s | FileCheck %s
 
 define void @invariant_load(i64 %n, i32* noalias nocapture %a, i32* nocapture readonly %b) {
 ; CHECK-LABEL: @invariant_load
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-large-strides.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-large-strides.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-large-strides.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-large-strides.ll
@@ -1,4 +1,4 @@
-; RUN: opt -mtriple aarch64-linux-gnu -mattr=+sve -loop-vectorize -dce -instcombine -S <%s | FileCheck %s
+; RUN: opt -mtriple aarch64-linux-gnu -mattr=+sve -loop-vectorize -scalable-vectorization=on -dce -instcombine -S <%s | FileCheck %s
 
 define void @stride7_i32(i32* noalias nocapture %dst, i64 %n) {
 ; CHECK-LABEL: @stride7_i32(
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-masked-loadstore.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-masked-loadstore.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-masked-loadstore.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-masked-loadstore.ll
@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -mattr=+sve -S %s -o - | FileCheck %s
+; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -mattr=+sve -S %s -scalable-vectorization=on -o - | FileCheck %s
 
 define void @mloadstore_f32(float* noalias nocapture %a, float* noalias nocapture readonly %b, i64 %n) {
 ; CHECK-LABEL: @mloadstore_f32
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-type-conv.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-type-conv.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-type-conv.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-type-conv.ll
@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -dce -instcombine < %s -S | FileCheck %s
+; RUN: opt -loop-vectorize -scalable-vectorization=on -dce -instcombine < %s -S | FileCheck %s
 
 target triple = "aarch64-unknown-linux-gnu"
 
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse-mask4.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse-mask4.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse-mask4.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse-mask4.ll
@@ -10,7 +10,7 @@
 
 ; The test checks if the mask is being correctly created, reverted and used
 
-; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -S < %s | FileCheck %s
+; RUN: opt -loop-vectorize -scalable-vectorization=on -dce -instcombine -mtriple aarch64-linux-gnu -S < %s | FileCheck %s
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 target triple = "aarch64-unknown-linux-gnu"
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse.ll
@@ -4,7 +4,7 @@
 ;  for (int i = N-1; i >= 0; --i)
 ;    a[i] = b[i] + 1.0;
 
-; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -S < %s | FileCheck %s
+; RUN: opt -loop-vectorize -scalable-vectorization=on -dce -instcombine -mtriple aarch64-linux-gnu -S < %s | FileCheck %s
 
 define void @vector_reverse_f64(i64 %N, double* %a, double* %b) #0{
 ; CHECK-LABEL: @vector_reverse_f64
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-widen-phi.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-widen-phi.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-widen-phi.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-widen-phi.ll
@@ -1,4 +1,4 @@
-; RUN: opt -mtriple aarch64-linux-gnu -mattr=+sve -loop-vectorize -dce -instcombine -S < %s | FileCheck %s
+; RUN: opt -mtriple aarch64-linux-gnu -mattr=+sve -loop-vectorize -scalable-vectorization=on -dce -instcombine -S < %s | FileCheck %s
 
 ; Ensure that we can vectorize loops such as:
 ;   int *ptr = c;
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/scalable-vf-hint.ll b/llvm/test/Transforms/LoopVectorize/RISCV/scalable-vf-hint.ll
--- a/llvm/test/Transforms/LoopVectorize/RISCV/scalable-vf-hint.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/scalable-vf-hint.ll
@@ -1,5 +1,5 @@
 ; RUN: opt -mtriple=riscv64 -mattr=+m,+experimental-v -loop-vectorize \
-; RUN:   -riscv-v-vector-bits-max=512 -S < %s 2>&1 \
+; RUN:   -riscv-v-vector-bits-max=512 -S -scalable-vectorization=on < %s 2>&1 \
 ; RUN:   | FileCheck %s
 
 ; void test(int *a, int *b, int N) {
diff --git a/llvm/test/Transforms/LoopVectorize/metadata-width.ll b/llvm/test/Transforms/LoopVectorize/metadata-width.ll
--- a/llvm/test/Transforms/LoopVectorize/metadata-width.ll
+++ b/llvm/test/Transforms/LoopVectorize/metadata-width.ll
@@ -1,4 +1,5 @@
-; RUN: opt < %s  -loop-vectorize -force-vector-interleave=1 -force-target-supports-scalable-vectors=true -dce -instcombine -S | FileCheck %s
+; RUN: opt < %s  -loop-vectorize -force-vector-interleave=1 -force-target-supports-scalable-vectors=true -dce -instcombine -S -scalable-vectorization=on | FileCheck %s
+; RUN: opt < %s  -loop-vectorize -force-vector-interleave=1 -force-target-supports-scalable-vectors=true -dce -instcombine -S -scalable-vectorization=preferred | FileCheck %s
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 
@@ -65,11 +66,37 @@
   ret void
 }
 
+; Test that when only the width property is specified, and not the scalable.enable flag,
+; that the hint defaults to 'scalable.enable = false'.
+
+; CHECK-LABEL: @test4(
+; CHECK: store <8 x i32>
+; CHECK: ret void
+define void @test4(i32* nocapture %a, i32 %n) #0 {
+entry:
+  %cmp4 = icmp sgt i32 %n, 0
+  br i1 %cmp4, label %for.body, label %for.end
+
+for.body:                                         ; preds = %entry, %for.body
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
+  store i32 42, i32* %arrayidx, align 4
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !6
+
+for.end:                                          ; preds = %for.body, %entry
+  ret void
+}
+
 attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "frame-pointer"="none" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
 
-!0 = !{!0, !1}
+!0 = !{!0, !1, !5}
 !1 = !{!"llvm.loop.vectorize.width", i32 8}
 !2 = !{!2, !1, !3}
 !3 = !{!"llvm.loop.vectorize.scalable.enable", i32 1}
 !4 = !{!4, !1, !5}
 !5 = !{!"llvm.loop.vectorize.scalable.enable", i32 0}
+!6 = !{!6, !7}
+!7 = !{!"llvm.loop.vectorize.width", i32 8}
diff --git a/llvm/test/Transforms/LoopVectorize/optimal-epilog-vectorization-scalable.ll b/llvm/test/Transforms/LoopVectorize/optimal-epilog-vectorization-scalable.ll
--- a/llvm/test/Transforms/LoopVectorize/optimal-epilog-vectorization-scalable.ll
+++ b/llvm/test/Transforms/LoopVectorize/optimal-epilog-vectorization-scalable.ll
@@ -1,5 +1,5 @@
 ; REQUIRES: asserts
-; RUN: opt < %s  -passes='loop-vectorize' -force-vector-width=2 -force-target-supports-scalable-vectors=true -enable-epilogue-vectorization -epilogue-vectorization-force-VF=2 --debug-only=loop-vectorize -S 2>&1 | FileCheck %s
+; RUN: opt < %s  -passes='loop-vectorize' -force-vector-width=2 -force-target-supports-scalable-vectors=true -enable-epilogue-vectorization -epilogue-vectorization-force-VF=2 --debug-only=loop-vectorize -S -scalable-vectorization=on 2>&1 | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-n32:64-v256:256:256-v512:512:512"
 
diff --git a/llvm/test/Transforms/LoopVectorize/scalable-first-order-recurrence.ll b/llvm/test/Transforms/LoopVectorize/scalable-first-order-recurrence.ll
--- a/llvm/test/Transforms/LoopVectorize/scalable-first-order-recurrence.ll
+++ b/llvm/test/Transforms/LoopVectorize/scalable-first-order-recurrence.ll
@@ -1,5 +1,5 @@
-; RUN: opt -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -force-target-supports-scalable-vectors=true -S < %s | FileCheck %s --check-prefix=CHECK-VF4UF1
-; RUN: opt -loop-vectorize -force-vector-width=4 -force-vector-interleave=2 -force-target-supports-scalable-vectors=true -S < %s | FileCheck %s --check-prefix=CHECK-VF4UF2
+; RUN: opt -loop-vectorize -scalable-vectorization=on -force-vector-width=4 -force-vector-interleave=1 -force-target-supports-scalable-vectors=true -S < %s | FileCheck %s --check-prefix=CHECK-VF4UF1
+; RUN: opt -loop-vectorize -scalable-vectorization=on -force-vector-width=4 -force-vector-interleave=2 -force-target-supports-scalable-vectors=true -S < %s | FileCheck %s --check-prefix=CHECK-VF4UF2
 
 ; void recurrence_1(int *a, int *b, int n) {
 ;   for(int i = 0; i < n; i++)
diff --git a/llvm/test/Transforms/LoopVectorize/scalable-loop-unpredicated-body-scalar-tail.ll b/llvm/test/Transforms/LoopVectorize/scalable-loop-unpredicated-body-scalar-tail.ll
--- a/llvm/test/Transforms/LoopVectorize/scalable-loop-unpredicated-body-scalar-tail.ll
+++ b/llvm/test/Transforms/LoopVectorize/scalable-loop-unpredicated-body-scalar-tail.ll
@@ -1,5 +1,5 @@
-; RUN: opt -S -loop-vectorize -instcombine -force-vector-interleave=1 -force-vector-width=4 -force-target-supports-scalable-vectors=true < %s | FileCheck %s --check-prefix=CHECKUF1
-; RUN: opt -S -loop-vectorize -instcombine -force-vector-interleave=2 -force-vector-width=4 -force-target-supports-scalable-vectors=true < %s | FileCheck %s --check-prefix=CHECKUF2
+; RUN: opt -S -loop-vectorize -instcombine -force-vector-interleave=1 -force-vector-width=4 -force-target-supports-scalable-vectors=true -scalable-vectorization=on < %s | FileCheck %s --check-prefix=CHECKUF1
+; RUN: opt -S -loop-vectorize -instcombine -force-vector-interleave=2 -force-vector-width=4 -force-target-supports-scalable-vectors=true -scalable-vectorization=on < %s | FileCheck %s --check-prefix=CHECKUF2
 
 ; CHECKUF1: for.body.preheader:
 ; CHECKUF1-DAG: %wide.trip.count = zext i32 %N to i64
diff --git a/llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll b/llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll
--- a/llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll
+++ b/llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -loop-vectorize -force-target-supports-scalable-vectors=true -S | FileCheck %s
+; RUN: opt < %s -loop-vectorize -force-target-supports-scalable-vectors=true -scalable-vectorization=on -S | FileCheck %s
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 
diff --git a/llvm/test/Transforms/LoopVectorize/scalable-vf-hint.ll b/llvm/test/Transforms/LoopVectorize/scalable-vf-hint.ll
--- a/llvm/test/Transforms/LoopVectorize/scalable-vf-hint.ll
+++ b/llvm/test/Transforms/LoopVectorize/scalable-vf-hint.ll
@@ -1,5 +1,5 @@
 ; REQUIRES: asserts
-; RUN: opt -loop-vectorize -pass-remarks-analysis=loop-vectorize -debug-only=loop-vectorize -S < %s 2>&1 | FileCheck %s
+; RUN: opt -loop-vectorize -pass-remarks-analysis=loop-vectorize -debug-only=loop-vectorize -S -scalable-vectorization=on < %s 2>&1 | FileCheck %s
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"