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arm64: Use SignedOffset rather than PreIndexed addressing mode for callee-saved registers

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This also passes `fixed_frame_storage_size` (previously `total_sp_adjust`)
into `gen_clobber_save` so that it can be combined with other stack
adjustments.

Copyright (c) 2020, Arm Limited.
This commit is contained in:
Joey Gouly
2020-10-02 16:22:55 +01:00
parent d7fda6ac0e
commit eec60c9b06
5 changed files with 73 additions and 59 deletions
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98
cranelift/codegen/src/isa/aarch64/abi.rs
View File

@@ -129,6 +129,18 @@ impl Into<AMode> for StackAMode {
}
}
// Returns the size of stack space needed to store the
// `int_reg` and `vec_reg`.
fn saved_reg_stack_size(
int_reg: &[Writable<RealReg>],
vec_reg: &[Writable<RealReg>],
) -> (usize, usize) {
// Round up to multiple of 2, to keep 16-byte stack alignment.
let int_save_bytes = (int_reg.len() + (int_reg.len() & 1)) * 8;
let vec_save_bytes = vec_reg.len() * 16;
(int_save_bytes, vec_save_bytes)
}
/// AArch64-specific ABI behavior. This struct just serves as an implementation
/// point for the trait; it is never actually instantiated.
pub(crate) struct AArch64MachineDeps;
@@ -495,11 +507,18 @@ impl ABIMachineSpec for AArch64MachineDeps {
call_conv: isa::CallConv,
_: &settings::Flags,
clobbers: &Set<Writable<RealReg>>,
fixed_frame_storage_size: u32,
) -> (u64, SmallVec<[Inst; 16]>) {
let mut insts = SmallVec::new();
let (clobbered_int, clobbered_vec) = get_callee_saves(call_conv, clobbers);
let mut clobber_size = 0;
for reg_pair in clobbered_int.chunks(2) {
let (int_save_bytes, vec_save_bytes) = saved_reg_stack_size(&clobbered_int, &clobbered_vec);
let total_save_bytes = (vec_save_bytes + int_save_bytes) as i32;
insts.extend(Self::gen_sp_reg_adjust(
-(total_save_bytes + fixed_frame_storage_size as i32),
));
for (i, reg_pair) in clobbered_int.chunks(2).enumerate() {
let (r1, r2) = if reg_pair.len() == 2 {
// .to_reg().to_reg(): Writable<RealReg> --> RealReg --> Reg
(reg_pair[0].to_reg().to_reg(), reg_pair[1].to_reg().to_reg())
@@ -510,36 +529,30 @@ impl ABIMachineSpec for AArch64MachineDeps {
debug_assert!(r1.get_class() == RegClass::I64);
debug_assert!(r2.get_class() == RegClass::I64);
// stp r1, r2, [sp, #-16]!
// stp r1, r2, [sp, #(i * #16)]
insts.push(Inst::StoreP64 {
rt: r1,
rt2: r2,
mem: PairAMode::PreIndexed(
writable_stack_reg(),
SImm7Scaled::maybe_from_i64(-16, types::I64).unwrap(),
mem: PairAMode::SignedOffset(
stack_reg(),
SImm7Scaled::maybe_from_i64((i * 16) as i64, types::I64).unwrap(),
),
});
clobber_size += 16;
}
let vec_save_bytes = clobbered_vec.len() * 16;
if vec_save_bytes != 0 {
insts.push(Inst::AluRRImm12 {
alu_op: ALUOp::Sub64,
rd: writable_stack_reg(),
rn: stack_reg(),
imm12: Imm12::maybe_from_u64(vec_save_bytes as u64).unwrap(),
});
clobber_size += vec_save_bytes;
}
let vec_offset = int_save_bytes;
for (i, reg) in clobbered_vec.iter().enumerate() {
insts.push(Inst::FpuStore128 {
rd: reg.to_reg().to_reg(),
mem: AMode::Unscaled(stack_reg(), SImm9::maybe_from_i64((i * 16) as i64).unwrap()),
mem: AMode::Unscaled(
stack_reg(),
SImm9::maybe_from_i64((vec_offset + (i * 16)) as i64).unwrap(),
),
srcloc: None,
});
}
(clobber_size as u64, insts)
(total_save_bytes as u64, insts)
}
fn gen_clobber_restore(
@@ -550,24 +563,8 @@ impl ABIMachineSpec for AArch64MachineDeps {
let mut insts = SmallVec::new();
let (clobbered_int, clobbered_vec) = get_callee_saves(call_conv, clobbers);
for (i, reg) in clobbered_vec.iter().enumerate() {
insts.push(Inst::FpuLoad128 {
rd: Writable::from_reg(reg.to_reg().to_reg()),
mem: AMode::Unscaled(stack_reg(), SImm9::maybe_from_i64((i * 16) as i64).unwrap()),
srcloc: None,
});
}
let vec_save_bytes = clobbered_vec.len() * 16;
if vec_save_bytes != 0 {
insts.push(Inst::AluRRImm12 {
alu_op: ALUOp::Add64,
rd: writable_stack_reg(),
rn: stack_reg(),
imm12: Imm12::maybe_from_u64(vec_save_bytes as u64).unwrap(),
});
}
for reg_pair in clobbered_int.chunks(2).rev() {
let (int_save_bytes, vec_save_bytes) = saved_reg_stack_size(&clobbered_int, &clobbered_vec);
for (i, reg_pair) in clobbered_int.chunks(2).enumerate() {
let (r1, r2) = if reg_pair.len() == 2 {
(
reg_pair[0].map(|r| r.to_reg()),
@@ -580,17 +577,36 @@ impl ABIMachineSpec for AArch64MachineDeps {
debug_assert!(r1.to_reg().get_class() == RegClass::I64);
debug_assert!(r2.to_reg().get_class() == RegClass::I64);
// ldp r1, r2, [sp], #16
// ldp r1, r2, [sp, #(i * 16)]
insts.push(Inst::LoadP64 {
rt: r1,
rt2: r2,
mem: PairAMode::PostIndexed(
writable_stack_reg(),
SImm7Scaled::maybe_from_i64(16, types::I64).unwrap(),
mem: PairAMode::SignedOffset(
stack_reg(),
SImm7Scaled::maybe_from_i64((i * 16) as i64, types::I64).unwrap(),
),
});
}
for (i, reg) in clobbered_vec.iter().enumerate() {
insts.push(Inst::FpuLoad128 {
rd: Writable::from_reg(reg.to_reg().to_reg()),
mem: AMode::Unscaled(
stack_reg(),
SImm9::maybe_from_i64(((i * 16) + int_save_bytes) as i64).unwrap(),
),
srcloc: None,
});
}
// For non-baldrdash calling conventions, the frame pointer
// will be moved into the stack pointer in the epilogue, so we
// can skip restoring the stack pointer value with this `add`.
if call_conv.extends_baldrdash() {
let total_save_bytes = (int_save_bytes + vec_save_bytes) as i32;
insts.extend(Self::gen_sp_reg_adjust(total_save_bytes));
}
// If this is Baldrdash-2020, restore the callee (i.e., our) TLS
// register. We may have allocated it for something else and clobbered
// it, but the ABI expects us to leave the TLS register unchanged.