diff --git a/llvm/lib/Target/AVR/AVRISelLowering.cpp b/llvm/lib/Target/AVR/AVRISelLowering.cpp
--- a/llvm/lib/Target/AVR/AVRISelLowering.cpp
+++ b/llvm/lib/Target/AVR/AVRISelLowering.cpp
@@ -1496,9 +1496,11 @@
 
   // Create loop block.
   MachineBasicBlock *LoopBB = F->CreateMachineBasicBlock(LLVM_BB);
+  MachineBasicBlock *CheckBB = F->CreateMachineBasicBlock(LLVM_BB);
   MachineBasicBlock *RemBB = F->CreateMachineBasicBlock(LLVM_BB);
 
   F->insert(I, LoopBB);
+  F->insert(I, CheckBB);
   F->insert(I, RemBB);
 
   // Update machine-CFG edges by transferring all successors of the current
@@ -1507,14 +1509,14 @@
                 BB->end());
   RemBB->transferSuccessorsAndUpdatePHIs(BB);
 
-  // Add adges BB => LoopBB => RemBB, BB => RemBB, LoopBB => LoopBB.
-  BB->addSuccessor(LoopBB);
-  BB->addSuccessor(RemBB);
-  LoopBB->addSuccessor(RemBB);
-  LoopBB->addSuccessor(LoopBB);
+  // Add edges BB => LoopBB => CheckBB => RemBB, CheckBB => LoopBB.
+  BB->addSuccessor(CheckBB);
+  LoopBB->addSuccessor(CheckBB);
+  CheckBB->addSuccessor(LoopBB);
+  CheckBB->addSuccessor(RemBB);
 
-  Register ShiftAmtReg = RI.createVirtualRegister(&AVR::LD8RegClass);
-  Register ShiftAmtReg2 = RI.createVirtualRegister(&AVR::LD8RegClass);
+  Register ShiftAmtReg = RI.createVirtualRegister(&AVR::GPR8RegClass);
+  Register ShiftAmtReg2 = RI.createVirtualRegister(&AVR::GPR8RegClass);
   Register ShiftReg = RI.createVirtualRegister(RC);
   Register ShiftReg2 = RI.createVirtualRegister(RC);
   Register ShiftAmtSrcReg = MI.getOperand(2).getReg();
@@ -1522,44 +1524,41 @@
   Register DstReg = MI.getOperand(0).getReg();
 
   // BB:
-  // cpi N, 0
-  // breq RemBB
-  BuildMI(BB, dl, TII.get(AVR::CPIRdK)).addReg(ShiftAmtSrcReg).addImm(0);
-  BuildMI(BB, dl, TII.get(AVR::BREQk)).addMBB(RemBB);
+  // rjmp CheckBB
+  BuildMI(BB, dl, TII.get(AVR::RJMPk)).addMBB(CheckBB);
 
   // LoopBB:
-  // ShiftReg = phi [%SrcReg, BB], [%ShiftReg2, LoopBB]
-  // ShiftAmt = phi [%N, BB],      [%ShiftAmt2, LoopBB]
   // ShiftReg2 = shift ShiftReg
+  auto ShiftMI = BuildMI(LoopBB, dl, TII.get(Opc), ShiftReg2).addReg(ShiftReg);
+  if (HasRepeatedOperand)
+    ShiftMI.addReg(ShiftReg);
+
+  // CheckBB:
+  // ShiftReg = phi [%SrcReg, BB], [%ShiftReg2, LoopBB]
+  // ShiftAmt = phi [%N,      BB], [%ShiftAmt2, LoopBB]
+  // DestReg  = phi [%SrcReg, BB], [%ShiftReg,  LoopBB]
   // ShiftAmt2 = ShiftAmt - 1;
-  BuildMI(LoopBB, dl, TII.get(AVR::PHI), ShiftReg)
+  // if (ShiftAmt2 >= 0) goto LoopBB;
+  BuildMI(CheckBB, dl, TII.get(AVR::PHI), ShiftReg)
       .addReg(SrcReg)
       .addMBB(BB)
       .addReg(ShiftReg2)
       .addMBB(LoopBB);
-  BuildMI(LoopBB, dl, TII.get(AVR::PHI), ShiftAmtReg)
+  BuildMI(CheckBB, dl, TII.get(AVR::PHI), ShiftAmtReg)
       .addReg(ShiftAmtSrcReg)
       .addMBB(BB)
       .addReg(ShiftAmtReg2)
       .addMBB(LoopBB);
-
-  auto ShiftMI = BuildMI(LoopBB, dl, TII.get(Opc), ShiftReg2).addReg(ShiftReg);
-  if (HasRepeatedOperand)
-    ShiftMI.addReg(ShiftReg);
-
-  BuildMI(LoopBB, dl, TII.get(AVR::SUBIRdK), ShiftAmtReg2)
-      .addReg(ShiftAmtReg)
-      .addImm(1);
-  BuildMI(LoopBB, dl, TII.get(AVR::BRNEk)).addMBB(LoopBB);
-
-  // RemBB:
-  // DestReg = phi [%SrcReg, BB], [%ShiftReg, LoopBB]
-  BuildMI(*RemBB, RemBB->begin(), dl, TII.get(AVR::PHI), DstReg)
+  BuildMI(CheckBB, dl, TII.get(AVR::PHI), DstReg)
       .addReg(SrcReg)
       .addMBB(BB)
       .addReg(ShiftReg2)
       .addMBB(LoopBB);
 
+  BuildMI(CheckBB, dl, TII.get(AVR::DECRd), ShiftAmtReg2)
+      .addReg(ShiftAmtReg);
+  BuildMI(CheckBB, dl, TII.get(AVR::BRPLk)).addMBB(LoopBB);
+
   MI.eraseFromParent(); // The pseudo instruction is gone now.
   return RemBB;
 }
diff --git a/llvm/test/CodeGen/AVR/rot.ll b/llvm/test/CodeGen/AVR/rot.ll
--- a/llvm/test/CodeGen/AVR/rot.ll
+++ b/llvm/test/CodeGen/AVR/rot.ll
@@ -6,14 +6,14 @@
 define i8 @rol8(i8 %val, i8 %amt) {
   ; CHECK:      andi r22, 7
 
-  ; CHECK-NEXT: cpi r22, 0
-  ; CHECK-NEXT: breq .LBB0_2
+  ; CHECK-NEXT: dec r22
+  ; CHECK-NEXT: brmi .LBB0_2
 
 ; CHECK-NEXT: .LBB0_1:
   ; CHECK-NEXT: lsl r24
   ; CHECK-NEXT: adc r24, r1
-  ; CHECK-NEXT: subi r22, 1
-  ; CHECK-NEXT: brne .LBB0_1
+  ; CHECK-NEXT: dec r22
+  ; CHECK-NEXT: brpl .LBB0_1
 
 ; CHECK-NEXT: .LBB0_2:
   ; CHECK-NEXT: ret
@@ -33,16 +33,16 @@
 define i8 @ror8(i8 %val, i8 %amt) {
   ; CHECK:      andi r22, 7
 
-  ; CHECK-NEXT: cpi r22, 0
-  ; CHECK-NEXT: breq .LBB1_2
+  ; CHECK-NEXT: dec r22
+  ; CHECK-NEXT: brmi .LBB1_2
 
 ; CHECK-NEXT: .LBB1_1:
   ; CHECK-NEXT: lsr r24
   ; CHECK-NEXT: ldi r0, 0
   ; CHECK-NEXT: ror r0
   ; CHECK-NEXT: or r24, r0
-  ; CHECK-NEXT: subi r22, 1
-  ; CHECK-NEXT: brne .LBB1_1
+  ; CHECK-NEXT: dec r22
+  ; CHECK-NEXT: brpl .LBB1_1
 
 ; CHECK-NEXT: .LBB1_2:
   ; CHECK-NEXT: ret
diff --git a/llvm/test/CodeGen/AVR/shift.ll b/llvm/test/CodeGen/AVR/shift.ll
--- a/llvm/test/CodeGen/AVR/shift.ll
+++ b/llvm/test/CodeGen/AVR/shift.ll
@@ -1,5 +1,49 @@
 ; RUN: llc < %s -march=avr | FileCheck %s
 
+; Optimize for speed.
+; CHECK-LABEL: shift_i8_i8_speed
+define i8 @shift_i8_i8_speed(i8 %a, i8 %b) {
+  ; CHECK:        dec r22
+  ; CHECK-NEXT:   brmi .LBB0_2
+  ; CHECK-NEXT: .LBB0_1:
+  ; CHECK-NEXT:   lsl r24
+  ; CHECK-NEXT:   dec r22
+  ; CHECK-NEXT:   brpl .LBB0_1
+  ; CHECK-NEXT: .LBB0_2:
+  ; CHECK-NEXT:   ret
+  %result = shl i8 %a, %b
+  ret i8 %result
+}
+
+; Optimize for size (producing slightly smaller code).
+; CHECK-LABEL: shift_i8_i8_size
+define i8 @shift_i8_i8_size(i8 %a, i8 %b) optsize {
+  ; CHECK:      .LBB1_1:
+  ; CHECK-NEXT:   dec r22
+  ; CHECK-NEXT:   brmi .LBB1_3
+  ; CHECK:        lsl r24
+  ; CHECK-NEXT:   rjmp .LBB1_1
+  ; CHECK-NEXT: .LBB1_3:
+  ; CHECK-NEXT:   ret
+  %result = shl i8 %a, %b
+  ret i8 %result
+}
+
+; CHECK-LABEL: shift_i16_i16
+define i16 @shift_i16_i16(i16 %a, i16 %b) {
+  ; CHECK:        dec r22
+  ; CHECK-NEXT:   brmi .LBB2_2
+  ; CHECK-NEXT: .LBB2_1:
+  ; CHECK-NEXT:   lsl r24
+  ; CHECK-NEXT:   rol r25
+  ; CHECK-NEXT:   dec r22
+  ; CHECK-NEXT:   brpl .LBB2_1
+  ; CHECK-NEXT: .LBB2_2:
+  ; CHECK-NEXT:   ret
+  %result = shl i16 %a, %b
+  ret i16 %result
+}
+
 ; CHECK-LABEL: shift_i64_i64
 define i64 @shift_i64_i64(i64 %a, i64 %b) {
   ; CHECK: call    __ashldi3