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WIP: cranelift: omit function prologue and epilogue on x64 if possible #8516

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WIP: cranelift: omit function prologue and epilogue on x64 if possible #8516

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73 changes: 46 additions & 27 deletions cranelift/codegen/src/isa/x64/abi.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -535,25 +535,29 @@ impl ABIMachineSpec for X64ABIMachineSpec {
_isa_flags: &x64_settings::Flags,
frame_layout: &FrameLayout,
) -> SmallInstVec<Self::I> {
let r_rsp = regs::rsp();
let r_rbp = regs::rbp();
let w_rbp = Writable::from_reg(r_rbp);
let setup_frame = frame_layout.setup_area_size > 0;
let mut insts = SmallVec::new();
// `push %rbp`
// RSP before the call will be 0 % 16. So here, it is 8 % 16.
insts.push(Inst::push64(RegMemImm::reg(r_rbp)));

if flags.unwind_info() {
insts.push(Inst::Unwind {
inst: UnwindInst::PushFrameRegs {
offset_upward_to_caller_sp: frame_layout.setup_area_size,
},
});
}
if setup_frame {
let r_rsp = regs::rsp();
let r_rbp = regs::rbp();
let w_rbp = Writable::from_reg(r_rbp);
// `push %rbp`
// RSP before the call will be 0 % 16. So here, it is 8 % 16.
insts.push(Inst::push64(RegMemImm::reg(r_rbp)));

// `mov %rsp, %rbp`
// RSP is now 0 % 16
insts.push(Inst::mov_r_r(OperandSize::Size64, r_rsp, w_rbp));
if flags.unwind_info() {
insts.push(Inst::Unwind {
inst: UnwindInst::PushFrameRegs {
offset_upward_to_caller_sp: frame_layout.setup_area_size,
},
});
}

// `mov %rsp, %rbp`
// RSP is now 0 % 16
insts.push(Inst::mov_r_r(OperandSize::Size64, r_rsp, w_rbp));
}

insts
}
Expand All @@ -562,17 +566,21 @@ impl ABIMachineSpec for X64ABIMachineSpec {
_call_conv: isa::CallConv,
_flags: &settings::Flags,
_isa_flags: &x64_settings::Flags,
_frame_layout: &FrameLayout,
frame_layout: &FrameLayout,
) -> SmallInstVec<Self::I> {
let setup_frame = frame_layout.setup_area_size > 0;
let mut insts = SmallVec::new();
// `mov %rbp, %rsp`
insts.push(Inst::mov_r_r(
OperandSize::Size64,
regs::rbp(),
Writable::from_reg(regs::rsp()),
));
// `pop %rbp`
insts.push(Inst::pop64(Writable::from_reg(regs::rbp())));

if setup_frame {
// `mov %rbp, %rsp`
insts.push(Inst::mov_r_r(
OperandSize::Size64,
regs::rbp(),
Writable::from_reg(regs::rsp()),
));
// `pop %rbp`
insts.push(Inst::pop64(Writable::from_reg(regs::rbp())));
}
insts
}

Expand Down Expand Up @@ -966,7 +974,7 @@ impl ABIMachineSpec for X64ABIMachineSpec {
flags: &settings::Flags,
_sig: &Signature,
regs: &[Writable<RealReg>],
_is_leaf: bool,
is_leaf: bool,
incoming_args_size: u32,
tail_args_size: u32,
fixed_frame_storage_size: u32,
Expand Down Expand Up @@ -999,7 +1007,18 @@ impl ABIMachineSpec for X64ABIMachineSpec {
let clobber_size = compute_clobber_size(&regs);

// Compute setup area size.
let setup_area_size = 16; // RBP, return address
let setup_area_size = if flags.preserve_frame_pointers()
|| !dbg!(is_leaf)
|| incoming_args_size > 0
|| clobber_size > 0
|| fixed_frame_storage_size > 0
{
16 // RBP, return address
} else {
0
};

dbg!(setup_area_size);

// Return FrameLayout structure.
FrameLayout {
Expand Down