Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -20266,7 +20266,15 @@
 
   // Replace a SCALAR_TO_VECTOR(EXTRACT_VECTOR_ELT(V,C0)) pattern
   // with a VECTOR_SHUFFLE and possible truncate.
-  if (InVal.getOpcode() == ISD::EXTRACT_VECTOR_ELT) {
+
+  // We currently only perform this optimisation for fixed length vectors as
+  // the code assumes we know the vector length. In theory, we could do
+  // something similar using SPLAT_VECTORs for scalable vector types when
+  // extracting from an index less than the minimum number of elements.
+  // However, since we don't know if this is even profitable or not it seems
+  // better to bail out for now.
+  if (InVal.getOpcode() == ISD::EXTRACT_VECTOR_ELT &&
+      InVal->getOperand(0).getValueType().isFixedLengthVector()) {
     SDValue InVec = InVal->getOperand(0);
     SDValue EltNo = InVal->getOperand(1);
     auto InVecT = InVec.getValueType();
Index: llvm/test/CodeGen/AArch64/sve-fp.ll
===================================================================
--- llvm/test/CodeGen/AArch64/sve-fp.ll
+++ llvm/test/CodeGen/AArch64/sve-fp.ll
@@ -123,6 +123,19 @@
   ret <vscale x 2 x double> %res
 }
 
+%complex = type { { double, double } }
+
+define void @scalar_to_vector(%complex* %outval, <vscale x 2 x i1> %pred, <vscale x 2 x double> %in1, <vscale x 2 x double> %in2) {
+; CHECK-LABEL: foo1:
+  %realp = getelementptr inbounds %complex, %complex* %outval, i64 0, i32 0, i32 0
+  %imagp = getelementptr inbounds %complex, %complex* %outval, i64 0, i32 0, i32 1
+  %1 = call double @llvm.aarch64.sve.faddv.nxv2f64(<vscale x 2 x i1> %pred, <vscale x 2 x double> %in1)
+  %2 = call double @llvm.aarch64.sve.faddv.nxv2f64(<vscale x 2 x i1> %pred, <vscale x 2 x double> %in2)
+  store double %1, double* %realp, align 8
+  store double %2, double* %imagp, align 8
+  ret void
+}
+
 declare <vscale x 8 x half> @llvm.aarch64.sve.frecps.x.nxv8f16(<vscale x 8 x half>, <vscale x 8 x half>)
 declare <vscale x 4 x float>  @llvm.aarch64.sve.frecps.x.nxv4f32(<vscale x 4 x float> , <vscale x 4 x float>)
 declare <vscale x 2 x double> @llvm.aarch64.sve.frecps.x.nxv2f64(<vscale x 2 x double>, <vscale x 2 x double>)
@@ -130,3 +143,6 @@
 declare <vscale x 8 x half> @llvm.aarch64.sve.frsqrts.x.nxv8f16(<vscale x 8 x half>, <vscale x 8 x half>)
 declare <vscale x 4 x float> @llvm.aarch64.sve.frsqrts.x.nxv4f32(<vscale x 4 x float>, <vscale x 4 x float>)
 declare <vscale x 2 x double> @llvm.aarch64.sve.frsqrts.x.nxv2f64(<vscale x 2 x double>, <vscale x 2 x double>)
+
+; Function Attrs: nounwind readnone
+declare double @llvm.aarch64.sve.faddv.nxv2f64(<vscale x 2 x i1>, <vscale x 2 x double>) #2