Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -20610,7 +20610,7 @@
     // If the concatenated source types match this extract, it's a direct
     // simplification:
     // extract_subvec (concat V1, V2, ...), i --> Vi
-    if (ConcatSrcNumElts == ExtNumElts)
+    if (NVT.getVectorElementCount() == ConcatSrcVT.getVectorElementCount())
       return V.getOperand(ConcatOpIdx);
 
     // If the concatenated source vectors are a multiple length of this extract,
@@ -20618,7 +20618,8 @@
     // concat operand. Example:
     //   v2i8 extract_subvec (v16i8 concat (v8i8 X), (v8i8 Y), 14 -->
     //   v2i8 extract_subvec v8i8 Y, 6
-    if (NVT.isFixedLengthVector() && ConcatSrcNumElts % ExtNumElts == 0) {
+    if (NVT.isFixedLengthVector() && ConcatSrcVT.isFixedLengthVector() &&
+        ConcatSrcNumElts % ExtNumElts == 0) {
       SDLoc DL(N);
       unsigned NewExtIdx = ExtIdx - ConcatOpIdx * ConcatSrcNumElts;
       assert(NewExtIdx + ExtNumElts <= ConcatSrcNumElts &&
Index: llvm/test/CodeGen/AArch64/sve-extract-fixed-from-scalable-vector.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/sve-extract-fixed-from-scalable-vector.ll
@@ -0,0 +1,11 @@
+; RUN: not --crash llc -mtriple=aarch64-linux-gnu -mattr=+sve < %s -o - 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR
+
+; Extracting a fixed-length vector from an illegal subvector
+
+; CHECK-ERROR: ERROR: Extracting a fixed-length vector from an illegal scalable vector is not yet supported
+define <4 x i32> @extract_v4i32_nxv16i32_12(<vscale x 16 x i32> %arg) {
+  %ext = call <4 x i32> @llvm.experimental.vector.extract.v4i32.nxv16i32(<vscale x 16 x i32> %arg, i64 12)
+  ret <4 x i32> %ext
+}
+
+declare <4 x i32> @llvm.experimental.vector.extract.v4i32.nxv16i32(<vscale x 16 x i32>, i64)