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Cranelift: Simplify leaf functions that do not use the stack (#2960)

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* Cranelift AArch64: Simplify leaf functions that do not use the stack

Leaf functions that do not use the stack (e.g. do not clobber any
callee-saved registers) do not need a frame record.

Copyright (c) 2021, Arm Limited.
This commit is contained in:
Anton Kirilov
2021-08-27 11:12:37 +01:00
committed by GitHub
parent 12515e6646
commit 7b98be1bee
34 changed files with 650 additions and 1385 deletions
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89
cranelift/codegen/src/isa/x64/abi.rs
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@@ -496,18 +496,17 @@ impl ABIMachineSpec for X64ABIMachineSpec {
}
fn gen_clobber_save(
call_conv: isa::CallConv,
_call_conv: isa::CallConv,
setup_frame: bool,
flags: &settings::Flags,
clobbers: &Set<Writable<RealReg>>,
clobbered_callee_saves: &Vec<Writable<RealReg>>,
fixed_frame_storage_size: u32,
_outgoing_args_size: u32,
) -> (u64, SmallVec<[Self::I; 16]>) {
let mut insts = SmallVec::new();
// Find all clobbered registers that are callee-save.
let clobbered = get_callee_saves(&call_conv, clobbers);
let clobbered_size = compute_clobber_size(&clobbered);
let clobbered_size = compute_clobber_size(&clobbered_callee_saves);
if flags.unwind_info() {
if flags.unwind_info() && setup_frame {
// Emit unwind info: start the frame. The frame (from unwind
// consumers' point of view) starts at clobbbers, just below
// the FP and return address. Spill slots and stack slots are
@@ -534,7 +533,7 @@ impl ABIMachineSpec for X64ABIMachineSpec {
// Store each clobbered register in order at offsets from RSP,
// placing them above the fixed frame slots.
let mut cur_offset = fixed_frame_storage_size;
for reg in &clobbered {
for reg in clobbered_callee_saves {
let r_reg = reg.to_reg();
let off = cur_offset;
match r_reg.get_class() {
@@ -579,14 +578,14 @@ impl ABIMachineSpec for X64ABIMachineSpec {
) -> SmallVec<[Self::I; 16]> {
let mut insts = SmallVec::new();
let clobbered = get_callee_saves(&call_conv, clobbers);
let stack_size = fixed_frame_storage_size + compute_clobber_size(&clobbered);
let clobbered_callee_saves = Self::get_clobbered_callee_saves(call_conv, clobbers);
let stack_size = fixed_frame_storage_size + compute_clobber_size(&clobbered_callee_saves);
// Restore regs by loading from offsets of RSP. RSP will be
// returned to nominal-RSP at this point, so we can use the
// same offsets that we used when saving clobbers above.
let mut cur_offset = fixed_frame_storage_size;
for reg in &clobbered {
for reg in &clobbered_callee_saves {
let rreg = reg.to_reg();
match rreg.get_class() {
RegClass::I64 => {
@@ -797,6 +796,47 @@ impl ABIMachineSpec for X64ABIMachineSpec {
ir::ArgumentExtension::None
}
}
fn get_clobbered_callee_saves(
call_conv: CallConv,
regs: &Set<Writable<RealReg>>,
) -> Vec<Writable<RealReg>> {
let mut regs: Vec<Writable<RealReg>> = match call_conv {
CallConv::BaldrdashSystemV | CallConv::Baldrdash2020 => regs
.iter()
.cloned()
.filter(|r| is_callee_save_baldrdash(r.to_reg()))
.collect(),
CallConv::BaldrdashWindows => {
todo!("baldrdash windows");
}
CallConv::Fast | CallConv::Cold | CallConv::SystemV | CallConv::WasmtimeSystemV => regs
.iter()
.cloned()
.filter(|r| is_callee_save_systemv(r.to_reg()))
.collect(),
CallConv::WindowsFastcall | CallConv::WasmtimeFastcall => regs
.iter()
.cloned()
.filter(|r| is_callee_save_fastcall(r.to_reg()))
.collect(),
CallConv::Probestack => todo!("probestack?"),
CallConv::AppleAarch64 | CallConv::WasmtimeAppleAarch64 => unreachable!(),
};
// Sort registers for deterministic code output. We can do an unstable sort because the
// registers will be unique (there are no dups).
regs.sort_unstable_by_key(|r| r.to_reg().get_index());
regs
}
fn is_frame_setup_needed(
_is_leaf: bool,
_stack_args_size: u32,
_num_clobbered_callee_saves: usize,
_fixed_frame_storage_size: u32,
) -> bool {
true
}
}
impl From<StackAMode> for SyntheticAmode {
@@ -984,35 +1024,6 @@ fn is_callee_save_fastcall(r: RealReg) -> bool {
}
}
fn get_callee_saves(call_conv: &CallConv, regs: &Set<Writable<RealReg>>) -> Vec<Writable<RealReg>> {
let mut regs: Vec<Writable<RealReg>> = match call_conv {
CallConv::BaldrdashSystemV | CallConv::Baldrdash2020 => regs
.iter()
.cloned()
.filter(|r| is_callee_save_baldrdash(r.to_reg()))
.collect(),
CallConv::BaldrdashWindows => {
todo!("baldrdash windows");
}
CallConv::Fast | CallConv::Cold | CallConv::SystemV | CallConv::WasmtimeSystemV => regs
.iter()
.cloned()
.filter(|r| is_callee_save_systemv(r.to_reg()))
.collect(),
CallConv::WindowsFastcall | CallConv::WasmtimeFastcall => regs
.iter()
.cloned()
.filter(|r| is_callee_save_fastcall(r.to_reg()))
.collect(),
CallConv::Probestack => todo!("probestack?"),
CallConv::AppleAarch64 | CallConv::WasmtimeAppleAarch64 => unreachable!(),
};
// Sort registers for deterministic code output. We can do an unstable sort because the
// registers will be unique (there are no dups).
regs.sort_unstable_by_key(|r| r.to_reg().get_index());
regs
}
fn compute_clobber_size(clobbers: &Vec<Writable<RealReg>>) -> u32 {
let mut clobbered_size = 0;
for reg in clobbers {