From afff169f17cd66a9d0399c2ae560e12b4925ef25 Mon Sep 17 00:00:00 2001
From: Dylan McKay <dylanmckay34@gmail.com>
Date: Wed, 5 Oct 2016 13:38:29 +0000
Subject: [PATCH] [AVR] Don't select 'MOVW' instructions when they are not
 supported

We have a subtarget feature which we were ignoring, which was causing us
to generate unsupported instructions for some older chips.

llvm-svn: 283317
---
 llvm/lib/Target/AVR/AVRInstrInfo.cpp | 56 ++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 15 deletions(-)

diff --git a/llvm/lib/Target/AVR/AVRInstrInfo.cpp b/llvm/lib/Target/AVR/AVRInstrInfo.cpp
index 634d83d..88f8892 100644
--- a/llvm/lib/Target/AVR/AVRInstrInfo.cpp
+++ b/llvm/lib/Target/AVR/AVRInstrInfo.cpp
@@ -27,6 +27,7 @@
 
 #include "AVR.h"
 #include "AVRMachineFunctionInfo.h"
+#include "AVRRegisterInfo.h"
 #include "AVRTargetMachine.h"
 #include "MCTargetDesc/AVRMCTargetDesc.h"
 
@@ -42,22 +43,41 @@ void AVRInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
                                MachineBasicBlock::iterator MI,
                                const DebugLoc &DL, unsigned DestReg,
                                unsigned SrcReg, bool KillSrc) const {
+  const AVRSubtarget &STI = MBB.getParent()->getSubtarget<AVRSubtarget>();
+  const AVRRegisterInfo &TRI = *STI.getRegisterInfo();
   unsigned Opc;
 
-  if (AVR::GPR8RegClass.contains(DestReg, SrcReg)) {
-    Opc = AVR::MOVRdRr;
-  } else if (AVR::DREGSRegClass.contains(DestReg, SrcReg)) {
-    Opc = AVR::MOVWRdRr;
-  } else if (SrcReg == AVR::SP && AVR::DREGSRegClass.contains(DestReg)) {
-    Opc = AVR::SPREAD;
-  } else if (DestReg == AVR::SP && AVR::DREGSRegClass.contains(SrcReg)) {
-    Opc = AVR::SPWRITE;
+  // Not all AVR devices support the 16-bit `MOVW` instruction.
+  if (AVR::DREGSRegClass.contains(DestReg, SrcReg)) {
+    if (STI.hasMOVW()) {
+      BuildMI(MBB, MI, DL, get(AVR::MOVWRdRr), DestReg)
+          .addReg(SrcReg, getKillRegState(KillSrc));
+    } else {
+      unsigned DestLo, DestHi, SrcLo, SrcHi;
+
+      TRI.splitReg(DestReg, DestLo, DestHi);
+      TRI.splitReg(SrcReg,  SrcLo,  SrcHi);
+
+      // Copy each individual register with the `MOV` instruction.
+      BuildMI(MBB, MI, DL, get(AVR::MOVRdRr), DestLo)
+        .addReg(SrcLo, getKillRegState(KillSrc));
+      BuildMI(MBB, MI, DL, get(AVR::MOVRdRr), DestHi)
+        .addReg(SrcHi, getKillRegState(KillSrc));
+    }
   } else {
-    llvm_unreachable("Impossible reg-to-reg copy");
-  }
+    if (AVR::GPR8RegClass.contains(DestReg, SrcReg)) {
+      Opc = AVR::MOVRdRr;
+    } else if (SrcReg == AVR::SP && AVR::DREGSRegClass.contains(DestReg)) {
+      Opc = AVR::SPREAD;
+    } else if (DestReg == AVR::SP && AVR::DREGSRegClass.contains(SrcReg)) {
+      Opc = AVR::SPWRITE;
+    } else {
+      llvm_unreachable("Impossible reg-to-reg copy");
+    }
 
-  BuildMI(MBB, MI, DL, get(Opc), DestReg)
-      .addReg(SrcReg, getKillRegState(KillSrc));
+    BuildMI(MBB, MI, DL, get(Opc), DestReg)
+        .addReg(SrcReg, getKillRegState(KillSrc));
+  }
 }
 
 unsigned AVRInstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
@@ -105,6 +125,9 @@ void AVRInstrInfo::storeRegToStackSlot(MachineBasicBlock &MBB,
                                        const TargetRegisterClass *RC,
                                        const TargetRegisterInfo *TRI) const {
   MachineFunction &MF = *MBB.getParent();
+  AVRMachineFunctionInfo *AFI = MF.getInfo<AVRMachineFunctionInfo>();
+
+  AFI->setHasSpills(true);
 
   DebugLoc DL;
   if (MI != MBB.end()) {
@@ -460,9 +483,11 @@ unsigned AVRInstrInfo::getInstSizeInBytes(const MachineInstr &MI) const {
   case TargetOpcode::DBG_VALUE:
     return 0;
   case TargetOpcode::INLINEASM: {
-    const MachineFunction *MF = MI.getParent()->getParent();
-    const AVRTargetMachine &TM = static_cast<const AVRTargetMachine&>(MF->getTarget());
-    const TargetInstrInfo &TII = *TM.getSubtargetImpl()->getInstrInfo();
+    const MachineFunction &MF = *MI.getParent()->getParent();
+    const AVRTargetMachine &TM = static_cast<const AVRTargetMachine&>(MF.getTarget());
+    const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
+    const TargetInstrInfo &TII = *STI.getInstrInfo();
+
     return TII.getInlineAsmLength(MI.getOperand(0).getSymbolName(),
                                   *TM.getMCAsmInfo());
   }
@@ -470,3 +495,4 @@ unsigned AVRInstrInfo::getInstSizeInBytes(const MachineInstr &MI) const {
 }
 
 } // end of namespace llvm
+
-- 
2.7.4