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[AVR] fix interrupt stack pointer restoration #78

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Merged
merged 1 commit into from
Oct 2, 2020
Merged

[AVR] fix interrupt stack pointer restoration #78

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33 changes: 23 additions & 10 deletions llvm/lib/Target/AVR/AVRFrameLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,26 @@ void AVRFrameLowering::emitPrologue(MachineFunction &MF,
.setMIFlag(MachineInstr::FrameSetup);
}

static void restoreStatusRegister(MachineFunction &MF, MachineBasicBlock &MBB) {
const AVRMachineFunctionInfo *AFI = MF.getInfo<AVRMachineFunctionInfo>();

MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();

DebugLoc DL = MBBI->getDebugLoc();
const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
const AVRInstrInfo &TII = *STI.getInstrInfo();

// Emit special epilogue code to restore R1, R0 and SREG in interrupt/signal
// handlers at the very end of the function, just before reti.
if (AFI->isInterruptOrSignalHandler()) {
BuildMI(MBB, MBBI, DL, TII.get(AVR::POPRd), AVR::R0);
BuildMI(MBB, MBBI, DL, TII.get(AVR::OUTARr))
.addImm(0x3f)
.addReg(AVR::R0, RegState::Kill);
BuildMI(MBB, MBBI, DL, TII.get(AVR::POPWRd), AVR::R1R0);
}
}

void AVRFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
const AVRMachineFunctionInfo *AFI = MF.getInfo<AVRMachineFunctionInfo>();
Expand All @@ -151,18 +171,9 @@ void AVRFrameLowering::emitEpilogue(MachineFunction &MF,
const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
const AVRInstrInfo &TII = *STI.getInstrInfo();

// Emit special epilogue code to restore R1, R0 and SREG in interrupt/signal
// handlers at the very end of the function, just before reti.
if (AFI->isInterruptOrSignalHandler()) {
BuildMI(MBB, MBBI, DL, TII.get(AVR::POPRd), AVR::R0);
BuildMI(MBB, MBBI, DL, TII.get(AVR::OUTARr))
.addImm(0x3f)
.addReg(AVR::R0, RegState::Kill);
BuildMI(MBB, MBBI, DL, TII.get(AVR::POPWRd), AVR::R1R0);
}

// Early exit if there is no need to restore the frame pointer.
if (!FrameSize) {
restoreStatusRegister(MF, MBB);
return;
}

Expand Down Expand Up @@ -198,6 +209,8 @@ void AVRFrameLowering::emitEpilogue(MachineFunction &MF,
// Write back R29R28 to SP and temporarily disable interrupts.
BuildMI(MBB, MBBI, DL, TII.get(AVR::SPWRITE), AVR::SP)
.addReg(AVR::R29R28, RegState::Kill);

restoreStatusRegister(MF, MBB);
}

// Return true if the specified function should have a dedicated frame
Expand Down
35 changes: 35 additions & 0 deletions llvm/test/CodeGen/AVR/interrupts.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -64,5 +64,40 @@ define void @signal_handler_via_attribute() #1 {
ret void
}

define avr_intrcc void @interrupt_alloca() {
; CHECK-LABEL: interrupt_alloca:
; CHECK: sei
; CHECK-NEXT: push r0
; CHECK-NEXT: push r1
; CHECK-NEXT: in r0, 63
; CHECK-NEXT: push r0
; CHECK: clr r0
; CHECK: push r28
; CHECK-NEXT: push r29
; CHECK-NEXT: in r28, 61
; CHECK-NEXT: in r29, 62
; CHECK-NEXT: sbiw r28, 1
; CHECK-NEXT: in r0, 63
; CHECK-NEXT: cli
; CHECK-NEXT: out 62, r29
; CHECK-NEXT: out 63, r0
; CHECK-NEXT: out 61, r28
; CHECK: adiw r28, 1
; CHECK-NEXT: in r0, 63
; CHECK-NEXT: cli
; CHECK-NEXT: out 62, r29
; CHECK-NEXT: out 63, r0
; CHECK-NEXT: out 61, r28
; CHECK-NEXT: pop r29
; CHECK-NEXT: pop r28
; CHECK: pop r0
; CHECK-NEXT: out 63, r0
; CHECK-NEXT: pop r1
; CHECK-NEXT: pop r0
; CHECK-NEXT: reti
alloca i8
ret void
}

attributes #0 = { "interrupt" }
attributes #1 = { "signal" }