Index: llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -4096,13 +4096,14 @@
   // is a load, return the new registers in ValRegs. For a store, each elements
   // of ValRegs should be PartTy. Returns the next offset that needs to be
   // handled.
+  bool isBigEndian = MIRBuilder.getDataLayout().isBigEndian();
   auto MMO = LdStMI.getMMO();
   auto splitTypePieces = [=](LLT PartTy, SmallVectorImpl<Register> &ValRegs,
-                             unsigned Offset) -> unsigned {
+                             unsigned NumParts, unsigned Offset) -> unsigned {
     MachineFunction &MF = MIRBuilder.getMF();
     unsigned PartSize = PartTy.getSizeInBits();
     for (unsigned Idx = 0, E = NumParts; Idx != E && Offset < TotalSize;
-         Offset += PartSize, ++Idx) {
+         ++Idx) {
       unsigned ByteOffset = Offset / 8;
       Register NewAddrReg;
 
@@ -4118,16 +4119,19 @@
       } else {
         MIRBuilder.buildStore(ValRegs[Idx], NewAddrReg, *NewMMO);
       }
+      Offset = isBigEndian ? Offset - PartSize : Offset + PartSize;
     }
 
     return Offset;
   };
 
-  unsigned HandledOffset = splitTypePieces(NarrowTy, NarrowRegs, 0);
+  unsigned Offset = isBigEndian ? TotalSize - NarrowTy.getSizeInBits() : 0;
+  unsigned HandledOffset =
+      splitTypePieces(NarrowTy, NarrowRegs, NumParts, Offset);
 
   // Handle the rest of the register if this isn't an even type breakdown.
   if (LeftoverTy.isValid())
-    splitTypePieces(LeftoverTy, NarrowLeftoverRegs, HandledOffset);
+    splitTypePieces(LeftoverTy, NarrowLeftoverRegs, NumLeftover, HandledOffset);
 
   if (IsLoad) {
     insertParts(ValReg, ValTy, NarrowTy, NarrowRegs,
Index: llvm/test/CodeGen/M68k/GlobalISel/legalizer_load_store.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/M68k/GlobalISel/legalizer_load_store.ll
@@ -0,0 +1,31 @@
+; RUN: llc -mtriple=m68k -global-isel -stop-after=legalizer %s -o - | FileCheck %s
+
+define void @test_store_i64(i64* %0) nounwind {
+; CHECK-LABEL: name: test_store_i64
+; CHECK:  [[FI:%[0-9]+]]:_(p0) = G_FRAME_INDEX %fixed-stack.0
+; CHECK-NEXT:  [[PTR_Hi:%[0-9]+]]:_(p0) = G_LOAD [[FI]](p0)
+; CHECK-NEXT:  [[Lo:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
+; CHECK-NEXT:  [[Hi:%[0-9]+]]:_(s32) = G_CONSTANT i32 2
+; CHECK-NEXT:  [[Offset:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
+; CHECK-NEXT:  [[PTR_Lo:%[0-9]+]]:_(p0) = G_PTR_ADD [[PTR_Hi]], [[Offset]](s32)
+; CHECK-NEXT:  G_STORE [[Lo]](s32), [[PTR_Lo]](p0)
+; CHECK-NEXT:  G_STORE [[Hi]](s32), [[PTR_Hi]](p0)
+; CHECK-NEXT:  RTS
+  store i64 8589934593, i64* %0
+  ret void
+}
+
+define i64 @test_load_i64(i64* %0) nounwind {
+; CHECK-LABEL: name: test_load_i64
+; CHECK:       [[FI:%[0-9]+]]:_(p0) = G_FRAME_INDEX %fixed-stack.0
+; CHECK-NEXT:  [[PTR_Hi:%[0-9]+]]:_(p0) = G_LOAD [[FI]](p0)
+; CHECK-NEXT:  [[Offset:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
+; CHECK-NEXT:  [[PTR_Lo:%[0-9]+]]:_(p0) = G_PTR_ADD [[PTR_Hi]], [[Offset]](s32)
+; CHECK-NEXT:  [[Lo:%[0-9]+]]:_(s32) = G_LOAD [[PTR_Lo]]
+; CHECK-NEXT:  [[Hi:%[0-9]+]]:_(s32) = G_LOAD [[PTR_Hi]]
+; CHECK-NEXT:  $d1 = COPY [[Lo]]
+; CHECK-NEXT:  $d0 = COPY [[Hi]]
+; RTS implicit $d1, implicit $d0
+  %2 = load i64, i64* %0
+  ret i64 %2
+}
\ No newline at end of file