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mach backend: have mem_finalize return a SmallVec;

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This avoids a spurious reallocation of the SmallVec containing the
load_constants result to a Vec, which appeared in dhat profiles.
This commit is contained in:
Benjamin Bouvier
2020-06-01 14:45:51 +02:00
parent 1acbad089a
commit cfa0527794
1 changed files with 11 additions and 6 deletions
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17
cranelift/codegen/src/isa/aarch64/inst/emit.rs
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@@ -8,7 +8,6 @@ use crate::isa::aarch64::inst::*;
use regalloc::{Reg, RegClass, Writable};
use alloc::vec::Vec;
use core::convert::TryFrom;
use log::debug;
@@ -24,7 +23,11 @@ pub fn memlabel_finalize(_insn_off: CodeOffset, label: &MemLabel) -> i32 {
/// generic arbitrary stack offset) into real addressing modes, possibly by
/// emitting some helper instructions that come immediately before the use
/// of this amode.
pub fn mem_finalize(insn_off: CodeOffset, mem: &MemArg, state: &EmitState) -> (Vec<Inst>, MemArg) {
pub fn mem_finalize(
insn_off: CodeOffset,
mem: &MemArg,
state: &EmitState,
) -> (SmallVec<[Inst; 4]>, MemArg) {
match mem {
&MemArg::SPOffset(off) | &MemArg::FPOffset(off) | &MemArg::NominalSPOffset(off) => {
let basereg = match mem {
@@ -48,7 +51,7 @@ pub fn mem_finalize(insn_off: CodeOffset, mem: &MemArg, state: &EmitState) -> (V
if let Some(simm9) = SImm9::maybe_from_i64(off) {
let mem = MemArg::Unscaled(basereg, simm9);
(vec![], mem)
(smallvec![], mem)
} else {
let tmp = writable_spilltmp_reg();
let mut const_insts = Inst::load_constant(tmp, off as u64);
@@ -64,14 +67,16 @@ pub fn mem_finalize(insn_off: CodeOffset, mem: &MemArg, state: &EmitState) -> (V
extendop: ExtendOp::UXTX,
};
const_insts.push(add_inst);
(const_insts.to_vec(), MemArg::reg(tmp.to_reg()))
(const_insts, MemArg::reg(tmp.to_reg()))
}
}
&MemArg::Label(ref label) => {
let off = memlabel_finalize(insn_off, label);
(vec![], MemArg::Label(MemLabel::PCRel(off)))
(smallvec![], MemArg::Label(MemLabel::PCRel(off)))
}
_ => (vec![], mem.clone()),
_ => (smallvec![], mem.clone()),
}
}