diff --git a/llvm/include/llvm/CodeGen/BasicTTIImpl.h b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
--- a/llvm/include/llvm/CodeGen/BasicTTIImpl.h
+++ b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
@@ -84,13 +84,17 @@
 
   /// Estimate a cost of Broadcast as an extract and sequence of insert
   /// operations.
-  InstructionCost getBroadcastShuffleOverhead(FixedVectorType *VTy) {
+  InstructionCost getBroadcastShuffleOverhead(VectorType *VTy) {
+    // Don't know how many lanes scalable vector has, so return invalid.
+    if (isa<ScalableVectorType>(VTy))
+      return InstructionCost::getInvalid();
+
     InstructionCost Cost = 0;
     // Broadcast cost is equal to the cost of extracting the zero'th element
     // plus the cost of inserting it into every element of the result vector.
     Cost += thisT()->getVectorInstrCost(Instruction::ExtractElement, VTy, 0);
 
-    for (int i = 0, e = VTy->getNumElements(); i < e; ++i) {
+    for (int i = 0, e = VTy->getElementCount().getKnownMinValue(); i < e; ++i) {
       Cost += thisT()->getVectorInstrCost(Instruction::InsertElement, VTy, i);
     }
     return Cost;
@@ -872,10 +876,9 @@
   InstructionCost getShuffleCost(TTI::ShuffleKind Kind, VectorType *Tp,
                                  ArrayRef<int> Mask, int Index,
                                  VectorType *SubTp) {
-
     switch (improveShuffleKindFromMask(Kind, Mask)) {
     case TTI::SK_Broadcast:
-      return getBroadcastShuffleOverhead(cast<FixedVectorType>(Tp));
+      return getBroadcastShuffleOverhead(Tp);
     case TTI::SK_Select:
     case TTI::SK_Splice:
     case TTI::SK_Reverse:
diff --git a/llvm/test/Analysis/CostModel/RISCV/rvv-shuffle-broadcast.ll b/llvm/test/Analysis/CostModel/RISCV/rvv-shuffle-broadcast.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Analysis/CostModel/RISCV/rvv-shuffle-broadcast.ll
@@ -0,0 +1,36 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
+; Check getShuffleCost for SK_BroadCast with scalable vector
+
+; RUN: opt -cost-model -analyze -mtriple=riscv64 -mattr=+m,+experimental-v -scalable-vectorization=on  < %s | FileCheck %s
+
+define void  @broadcast() {
+; CHECK-LABEL: 'broadcast'
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %zero = shufflevector <vscale x 8 x i8> undef, <vscale x 8 x i8> undef, <vscale x 8 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %1 = shufflevector <vscale x 16 x i8> undef, <vscale x 16 x i8> undef, <vscale x 16 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %2 = shufflevector <vscale x 4 x i16> undef, <vscale x 4 x i16> undef, <vscale x 4 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %3 = shufflevector <vscale x 8 x i16> undef, <vscale x 8 x i16> undef, <vscale x 8 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %4 = shufflevector <vscale x 2 x i32> undef, <vscale x 2 x i32> undef, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %5 = shufflevector <vscale x 4 x i32> undef, <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %6 = shufflevector <vscale x 1 x i64> undef, <vscale x 1 x i64> undef, <vscale x 1 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %7 = shufflevector <vscale x 2 x i64> undef, <vscale x 2 x i64> undef, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %8 = shufflevector <vscale x 16 x i1> undef, <vscale x 16 x i1> undef, <vscale x 16 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %9 = shufflevector <vscale x 8 x i1> undef, <vscale x 8 x i1> undef, <vscale x 8 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %10 = shufflevector <vscale x 4 x i1> undef, <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Invalid cost for instruction: %11 = shufflevector <vscale x 2 x i1> undef, <vscale x 2 x i1> undef, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
+;
+  %zero = shufflevector <vscale x 8 x i8> undef, <vscale x 8 x i8> undef, <vscale x 8 x i32> zeroinitializer
+  %1 = shufflevector <vscale x 16 x i8> undef, <vscale x 16 x i8> undef, <vscale x 16 x i32> zeroinitializer
+  %2 = shufflevector <vscale x 4 x i16> undef, <vscale x 4 x i16> undef, <vscale x 4 x i32> zeroinitializer
+  %3 = shufflevector <vscale x 8 x i16> undef, <vscale x 8 x i16> undef, <vscale x 8 x i32> zeroinitializer
+  %4 = shufflevector <vscale x 2 x i32> undef, <vscale x 2 x i32> undef, <vscale x 2 x i32> zeroinitializer
+  %5 = shufflevector <vscale x 4 x i32> undef, <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer
+  %6 = shufflevector <vscale x 1 x i64> undef, <vscale x 1 x i64> undef, <vscale x 1 x i32> zeroinitializer
+  %7 = shufflevector <vscale x 2 x i64> undef, <vscale x 2 x i64> undef, <vscale x 2 x i32> zeroinitializer
+  %8 = shufflevector <vscale x 16 x i1> undef, <vscale x 16 x i1> undef, <vscale x 16 x i32> zeroinitializer
+  %9 = shufflevector <vscale x 8 x i1> undef, <vscale x 8 x i1> undef, <vscale x 8 x i32> zeroinitializer
+  %10 = shufflevector <vscale x 4 x i1> undef, <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer
+  %11 = shufflevector <vscale x 2 x i1> undef, <vscale x 2 x i1> undef, <vscale x 2 x i32> zeroinitializer
+  ret void
+}
+