Revert "[ARM] Correctly handle execute-only in EmitStructByval"

[Caslyn]

Summary

This reverts commit 210f61cbddeddac47b347db072d674ee142520f6.

llvm/lib/Target/ARM/ARMISelLowering.cpp

ARMTargetLowering::EmitStructByval(MachineInstr &MI,
   // Transfer the remainder of BB and its successor edges to exitMBB.
   exitMBB->splice(exitMBB->begin(), BB,
                   std::next(MachineBasicBlock::iterator(MI)), BB->end());
   exitMBB->transferSuccessorsAndUpdatePHIs(BB);
 
   // Load an immediate to varEnd.
   Register varEnd = MRI.createVirtualRegister(TRC);
   if (Subtarget->useMovt()) {
-    BuildMI(BB, dl, TII->get(IsThumb ? ARM::t2MOVi32imm : ARM::MOVi32imm),
-            varEnd)
-        .addImm(LoopSize);
-  } else if (Subtarget->genExecuteOnly()) {
-    assert(IsThumb && "Non-thumb expected to have used movt");
-    BuildMI(BB, dl, TII->get(ARM::tMOVi32imm), varEnd).addImm(LoopSize);
+    unsigned Vtmp = varEnd;
+    if ((LoopSize & 0xFFFF0000) != 0)
+      Vtmp = MRI.createVirtualRegister(TRC);
+    BuildMI(BB, dl, TII->get(IsThumb ? ARM::t2MOVi16 : ARM::MOVi16), Vtmp)
+        .addImm(LoopSize & 0xFFFF)
+        .add(predOps(ARMCC::AL));
+
+    if ((LoopSize & 0xFFFF0000) != 0)
+      BuildMI(BB, dl, TII->get(IsThumb ? ARM::t2MOVTi16 : ARM::MOVTi16), varEnd)
+          .addReg(Vtmp)
+          .addImm(LoopSize >> 16)
+          .add(predOps(ARMCC::AL));
   } else {
     MachineConstantPool *ConstantPool = MF->getConstantPool();
     Type *Int32Ty = Type::getInt32Ty(MF->getFunction().getContext());
     const Constant *C = ConstantInt::get(Int32Ty, LoopSize);
 
     // MachineConstantPool wants an explicit alignment.
     Align Alignment = MF->getDataLayout().getPrefTypeAlign(Int32Ty);
     unsigned Idx = ConstantPool->getConstantPoolIndex(C, Alignment);