diff --git a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
--- a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
@@ -1152,6 +1152,11 @@
     }
   }
 
+  // Type legalization (via getNumberOfParts) can't handle structs
+  if (TLI->getValueType(DL, Src, true) == MVT::Other)
+    return BaseT::getMemoryOpCost(Opcode, Src, Alignment, AddressSpace,
+                                  CostKind);
+
   unsigned NumOps =
     (Src->isVectorTy() ? getNumVectorRegs(Src) : getNumberOfParts(Src));
 
diff --git a/llvm/test/Analysis/CostModel/SystemZ/struct-cost-crash.ll b/llvm/test/Analysis/CostModel/SystemZ/struct-cost-crash.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Analysis/CostModel/SystemZ/struct-cost-crash.ll
@@ -0,0 +1,25 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -passes="print<cost-model>" 2>&1 -disable-output < %s | FileCheck %s
+;
+; Check that SystemZTTIImpl::getMemoryOpCost doesn't try to legalize structs,
+; which was failing llvm_unreachable in MVT::getVT.
+
+target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
+target triple = "s390x-unknown-linux-gnu"
+
+declare { i64, i32 } @bar()
+
+define i8 @foo() {
+; CHECK-LABEL: 'foo'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %1
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %2 = call { i64, i32 } @bar()
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: store { i64, i32 } %2, ptr inttoptr (i64 16 to ptr), align 16
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %1
+;
+  br label %1
+
+1:                                                ; preds = %1, %0
+  %2 = call { i64, i32 } @bar()
+  store { i64, i32 } %2, ptr inttoptr (i64 16 to ptr), align 16
+  br label %1
+}