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/dag-combine-store-merge.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/dag-combine-store-merge.ll
@@ -0,0 +1,52 @@
+; 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 like this:
+; llc: /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:6366: llvm::SDValue llvm::SelectionDAG::getNode(unsigned int, const llvm::SDLoc &, llvm::EVT, llvm::SDValue, llvm::SDValue, const llvm::SDNodeFlags): Assertion `N2C && "Extract subvector index must be a constant"' failed.
+; PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
+; Stack dump:
+; 0.	Program arguments: ./llvm-project/build-debug/bin/llc ./crash-reports/dagisel-aarch64/1.ll -mtriple=aarch64
+; 1.	Running pass 'Function Pass Manager' on module './crash-reports/dagisel-aarch64/1.ll'.
+; 2.	Running pass 'AArch64 Instruction Selection' on function '@f'
+;  #0 0x0000000003af78fa llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /llvm_path/llvm-project/llvm/lib/Support/Unix/Signals.inc:569:11
+;  #1 0x0000000003af7aab PrintStackTraceSignalHandler(void*) /llvm_path/llvm-project/llvm/lib/Support/Unix/Signals.inc:636:1
+;  #2 0x0000000003af60f6 llvm::sys::RunSignalHandlers() /llvm_path/llvm-project/llvm/lib/Support/Signals.cpp:104:5
+;  #3 0x0000000003af81d5 SignalHandler(int) /llvm_path/llvm-project/llvm/lib/Support/Unix/Signals.inc:407:1
+;  #4 0x00007f614194c980 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12980)
+;  #5 0x00007f614083ce87 raise /build/glibc-uZu3wS/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
+;  #6 0x00007f614083e7f1 abort /build/glibc-uZu3wS/glibc-2.27/stdlib/abort.c:81:0
+;  #7 0x00007f614082e3fa __assert_fail_base /build/glibc-uZu3wS/glibc-2.27/assert/assert.c:89:0
+;  #8 0x00007f614082e472 (/lib/x86_64-linux-gnu/libc.so.6+0x30472)
+;  #9 0x0000000003800507 llvm::SelectionDAG::getNode(unsigned int, llvm::SDLoc const&, llvm::EVT, llvm::SDValue, llvm::SDValue, llvm::SDNodeFlags) /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:6367:5
+; #10 0x00000000037dbf90 llvm::SelectionDAG::getNode(unsigned int, llvm::SDLoc const&, llvm::EVT, llvm::SDValue, llvm::SDValue) /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:5975:10
+; #11 0x00000000036b73d2 (anonymous namespace)::DAGCombiner::mergeStoresOfConstantsOrVecElts(llvm::SmallVectorImpl<(anonymous namespace)::DAGCombiner::MemOpLink>&, llvm::EVT, unsigned int, bool, bool, bool) /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:18329:23
+; #12 0x00000000036b209a (anonymous namespace)::DAGCombiner::tryStoreMergeOfExtracts(llvm::SmallVectorImpl<(anonymous namespace)::DAGCombiner::MemOpLink>&, unsigned int, llvm::EVT, llvm::SDNode*) /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:18866:19
+; #13 0x00000000036ac2f5 (anonymous namespace)::DAGCombiner::mergeConsecutiveStores(llvm::StoreSDNode*) /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:19229:21
+; #14 0x00000000036464e2 (anonymous namespace)::DAGCombiner::visitSTORE(llvm::SDNode*) /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:19538:12
+; #15 0x00000000035fd9a8 (anonymous namespace)::DAGCombiner::visit(llvm::SDNode*) /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1787:40
+; #16 0x00000000035fcae8 (anonymous namespace)::DAGCombiner::combine(llvm::SDNode*) /llvm_path/llvm-project/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1828:10
+
+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
+}