Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -18321,6 +18321,9 @@
           // We may need to add a bitcast here to get types to line up.
           if (MemVTScalarTy != Val.getValueType().getScalarType()) {
             Val = DAG.getBitcast(MemVT, Val);
+          } else if (MemVT.isVector() &&
+                     Val.getOpcode() == ISD::EXTRACT_VECTOR_ELT) {
+            Val = DAG.getNode(ISD::BUILD_VECTOR, DL, MemVT, Val);
           } else {
             unsigned OpC = MemVT.isVector() ? ISD::EXTRACT_SUBVECTOR
                                             : ISD::EXTRACT_VECTOR_ELT;
Index: llvm/test/CodeGen/AArch64/pr58350.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/pr58350.ll
@@ -0,0 +1,31 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=aarch64-none-linux-gnu | FileCheck %s
+
+; This used to hit an assertion caused by dagcombine merge store.
+; When the store memVT is v1f32 and the other store to be merged
+; is f32, we need to build vector for the f32 store.
+
+define void @f(<1 x float> %a, i64 %b) {
+; CHECK-LABEL: f:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    sub sp, sp, #16
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    adrp x8, .LCPI0_0
+; CHECK-NEXT:    and x9, x0, #0x1
+; CHECK-NEXT:    mov x10, sp
+; CHECK-NEXT:    // kill: def $d0 killed $d0 def $q0
+; CHECK-NEXT:    ldr d1, [x8, :lo12:.LCPI0_0]
+; CHECK-NEXT:    bfi x10, x9, #2, #1
+; CHECK-NEXT:    str d1, [sp]
+; CHECK-NEXT:    ldr s1, [x10]
+; CHECK-NEXT:    mov v1.s[1], v0.s[0]
+; CHECK-NEXT:    str d1, [sp, #8]
+; CHECK-NEXT:    add sp, sp, #16
+; CHECK-NEXT:    ret
+  %P = alloca i64
+  %E = extractelement <2 x float> <float 0.5, float 1.0>, i64 %b
+  %G = getelementptr <1 x float>, ptr %P, i64 1
+  store float %E, ptr %P
+  store <1 x float> %a, ptr %G
+  ret void
+}