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
@@ -1004,6 +1004,10 @@
                                           CostKind, I));
       }
 
+      // Scalarization cost is Invalid, can't assume any num elements.
+      if (isa<ScalableVectorType>(DstVTy))
+        return InstructionCost::getInvalid();
+
       // In other cases where the source or destination are illegal, assume
       // the operation will get scalarized.
       unsigned Num = cast<FixedVectorType>(DstVTy)->getNumElements();
diff --git a/llvm/test/Analysis/CostModel/AArch64/sve-fptoi.ll b/llvm/test/Analysis/CostModel/AArch64/sve-fptoi.ll
--- a/llvm/test/Analysis/CostModel/AArch64/sve-fptoi.ll
+++ b/llvm/test/Analysis/CostModel/AArch64/sve-fptoi.ll
@@ -5,6 +5,24 @@
 
 define void @sve-fptoi() {
 ; CHECK-LABEL: 'sve-fptoi'
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f16_to_si8 = fptosi <vscale x 1 x half> undef to <vscale x 1 x i8>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f16_to_ui8 = fptoui <vscale x 1 x half> undef to <vscale x 1 x i8>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f16_to_si32 = fptosi <vscale x 1 x half> undef to <vscale x 1 x i32>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f16_to_ui32 = fptoui <vscale x 1 x half> undef to <vscale x 1 x i32>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f16_to_si64 = fptosi <vscale x 1 x half> undef to <vscale x 1 x i64>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f16_to_ui64 = fptoui <vscale x 1 x half> undef to <vscale x 1 x i64>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f32_to_si8 = fptosi <vscale x 1 x float> undef to <vscale x 1 x i8>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f32_to_ui8 = fptoui <vscale x 1 x float> undef to <vscale x 1 x i8>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f32_to_si16 = fptosi <vscale x 1 x float> undef to <vscale x 1 x i16>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f32_to_ui16 = fptoui <vscale x 1 x float> undef to <vscale x 1 x i16>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f32_to_si64 = fptosi <vscale x 1 x float> undef to <vscale x 1 x i64>
+; CHECK-NEXT: Cost Model: Invalid cost for instruction: %nv1f32_to_ui64 = fptoui <vscale x 1 x float> undef to <vscale x 1 x i64>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv1f64_to_si8 = fptosi <vscale x 1 x double> undef to <vscale x 1 x i8>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv1f64_to_ui8 = fptoui <vscale x 1 x double> undef to <vscale x 1 x i8>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv1f64_to_si16 = fptosi <vscale x 1 x double> undef to <vscale x 1 x i16>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv1f64_to_ui16 = fptoui <vscale x 1 x double> undef to <vscale x 1 x i16>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv1f64_to_si32 = fptosi <vscale x 1 x double> undef to <vscale x 1 x i32>
+; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv1f64_to_ui32 = fptoui <vscale x 1 x double> undef to <vscale x 1 x i32>
 ; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv2f16_to_si8 = fptosi <vscale x 2 x half> undef to <vscale x 2 x i8>
 ; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv2f16_to_ui8 = fptoui <vscale x 2 x half> undef to <vscale x 2 x i8>
 ; CHECK-NEXT: Cost Model: Found an estimated cost of 1 for instruction:   %nv2f16_to_si32 = fptosi <vscale x 2 x half> undef to <vscale x 2 x i32>
@@ -59,6 +77,26 @@
 ; CHECK-NEXT: Cost Model: Found an estimated cost of 7 for instruction:   %nv8f64_to_ui16 = fptoui <vscale x 8 x double> undef to <vscale x 8 x i16>
 ; CHECK-NEXT: Cost Model: Found an estimated cost of 6 for instruction:   %nv8f64_to_si32 = fptosi <vscale x 8 x double> undef to <vscale x 8 x i32>
 ; CHECK-NEXT: Cost Model: Found an estimated cost of 6 for instruction:   %nv8f64_to_ui32 = fptoui <vscale x 8 x double> undef to <vscale x 8 x i32>
+  %nv1f16_to_si8  = fptosi <vscale x 1 x half> undef to <vscale x 1 x i8>
+  %nv1f16_to_ui8  = fptoui <vscale x 1 x half> undef to <vscale x 1 x i8>
+  %nv1f16_to_si32 = fptosi <vscale x 1 x half> undef to <vscale x 1 x i32>
+  %nv1f16_to_ui32 = fptoui <vscale x 1 x half> undef to <vscale x 1 x i32>
+  %nv1f16_to_si64 = fptosi <vscale x 1 x half> undef to <vscale x 1 x i64>
+  %nv1f16_to_ui64 = fptoui <vscale x 1 x half> undef to <vscale x 1 x i64>
+
+  %nv1f32_to_si8  = fptosi <vscale x 1 x float> undef to <vscale x 1 x i8>
+  %nv1f32_to_ui8  = fptoui <vscale x 1 x float> undef to <vscale x 1 x i8>
+  %nv1f32_to_si16 = fptosi <vscale x 1 x float> undef to <vscale x 1 x i16>
+  %nv1f32_to_ui16 = fptoui <vscale x 1 x float> undef to <vscale x 1 x i16>
+  %nv1f32_to_si64 = fptosi <vscale x 1 x float> undef to <vscale x 1 x i64>
+  %nv1f32_to_ui64 = fptoui <vscale x 1 x float> undef to <vscale x 1 x i64>
+
+  %nv1f64_to_si8  = fptosi <vscale x 1 x double> undef to <vscale x 1 x i8>
+  %nv1f64_to_ui8  = fptoui <vscale x 1 x double> undef to <vscale x 1 x i8>
+  %nv1f64_to_si16 = fptosi <vscale x 1 x double> undef to <vscale x 1 x i16>
+  %nv1f64_to_ui16 = fptoui <vscale x 1 x double> undef to <vscale x 1 x i16>
+  %nv1f64_to_si32 = fptosi <vscale x 1 x double> undef to <vscale x 1 x i32>
+  %nv1f64_to_ui32 = fptoui <vscale x 1 x double> undef to <vscale x 1 x i32>
 
   %nv2f16_to_si8  = fptosi <vscale x 2 x half> undef to <vscale x 2 x i8>
   %nv2f16_to_ui8  = fptoui <vscale x 2 x half> undef to <vscale x 2 x i8>