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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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52
cranelift/codegen/src/isa/aarch64/abi.rs
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@@ -693,20 +693,30 @@ impl ABIMachineSpec for AArch64MachineDeps {
// nominal SP offset; abi_impl generic code will do that.
fn gen_clobber_save(
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<[Inst; 16]>) {
let mut insts = SmallVec::new();
let (clobbered_int, clobbered_vec) = get_regs_saved_in_prologue(call_conv, clobbers);
let mut clobbered_int = vec![];
let mut clobbered_vec = vec![];
for &reg in clobbered_callee_saves.iter() {
match reg.to_reg().get_class() {
RegClass::I64 => clobbered_int.push(reg),
RegClass::V128 => clobbered_vec.push(reg),
class => panic!("Unexpected RegClass: {:?}", class),
}
}
let (int_save_bytes, vec_save_bytes) =
saved_reg_stack_size(call_conv, &clobbered_int, &clobbered_vec);
let total_save_bytes = int_save_bytes + vec_save_bytes;
let clobber_size = total_save_bytes as i32;
let mut insts = SmallVec::new();
if flags.unwind_info() {
if flags.unwind_info() && setup_frame {
// The *unwind* frame (but not the actual frame) starts at the
// clobbers, just below the saved FP/LR pair.
insts.push(Inst::Unwind {
@@ -916,7 +926,7 @@ impl ABIMachineSpec for AArch64MachineDeps {
_outgoing_args_size: u32,
) -> SmallVec<[Inst; 16]> {
let mut insts = SmallVec::new();
let (clobbered_int, clobbered_vec) = get_regs_saved_in_prologue(call_conv, clobbers);
let (clobbered_int, clobbered_vec) = get_regs_restored_in_epilogue(call_conv, clobbers);
// Free the fixed frame if necessary.
if fixed_frame_storage_size > 0 {
@@ -1180,6 +1190,36 @@ impl ABIMachineSpec for AArch64MachineDeps {
ir::ArgumentExtension::None
}
}
fn get_clobbered_callee_saves(
call_conv: isa::CallConv,
regs: &Set<Writable<RealReg>>,
) -> Vec<Writable<RealReg>> {
let mut regs: Vec<Writable<RealReg>> = regs
.iter()
.cloned()
.filter(|r| is_reg_saved_in_prologue(call_conv, r.to_reg()))
.collect();
// 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 {
!is_leaf
// The function arguments that are passed on the stack are addressed
// relative to the Frame Pointer.
|| stack_args_size > 0
|| num_clobbered_callee_saves > 0
|| fixed_frame_storage_size > 0
}
}
/// Is this type supposed to be seen on this machine? E.g. references of the
@@ -1224,7 +1264,7 @@ fn is_reg_saved_in_prologue(call_conv: isa::CallConv, r: RealReg) -> bool {
/// Return the set of all integer and vector registers that must be saved in the
/// prologue and restored in the epilogue, given the set of all registers
/// written by the function's body.
fn get_regs_saved_in_prologue(
fn get_regs_restored_in_epilogue(
call_conv: isa::CallConv,
regs: &Set<Writable<RealReg>>,
) -> (Vec<Writable<RealReg>>, Vec<Writable<RealReg>>) {