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YJIT: Optimize putobject+opt_ltlt for integers #10401

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Mar 28, 2024
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YJIT: Optimize putobject+opt_ltlt for integers #10401

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17 changes: 17 additions & 0 deletions bootstraptest/test_yjit.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -4769,3 +4769,20 @@ def tests

tests
}

# test integer left shift with constant rhs
assert_equal [0x80000000000, 'a+', :ok].inspect, %q{
def shift(val) = val << 43

def tests
int = shift(1)
str = shift("a")

Integer.define_method(:<<) { |_| :ok }
redef = shift(1)

[int, str, redef]
end

tests
}
137 changes: 81 additions & 56 deletions yjit/src/codegen.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@ pub use crate::virtualmem::CodePtr;
/// Status returned by code generation functions
#[derive(PartialEq, Debug)]
enum CodegenStatus {
SkipNextInsn,
KeepCompiling,
EndBlock,
}
Expand Down Expand Up @@ -1197,6 +1198,13 @@ pub fn gen_single_block(
// Move to the next instruction to compile
insn_idx += insn_len(opcode) as u16;

// Move past next instruction when instructed
if status == Some(SkipNextInsn) {
let next_pc = unsafe { rb_iseq_pc_at_idx(iseq, insn_idx.into()) };
let next_opcode: usize = unsafe { rb_iseq_opcode_at_pc(iseq, next_pc) }.try_into().unwrap();
insn_idx += insn_len(next_opcode) as u16;
}

// If the instruction terminates this block
if status == Some(EndBlock) {
break;
Expand Down Expand Up @@ -1343,30 +1351,94 @@ fn jit_putobject(asm: &mut Assembler, arg: VALUE) {
fn gen_putobject_int2fix(
jit: &mut JITState,
asm: &mut Assembler,
_ocb: &mut OutlinedCb,
ocb: &mut OutlinedCb,
) -> Option<CodegenStatus> {
let opcode = jit.opcode;
let cst_val: usize = if opcode == YARVINSN_putobject_INT2FIX_0_.as_usize() {
0
} else {
1
};
let cst_val = VALUE::fixnum_from_usize(cst_val);

if let Some(result) = fuse_putobject_opt_ltlt(jit, asm, cst_val, ocb) {
return Some(result);
}

jit_putobject(asm, VALUE::fixnum_from_usize(cst_val));
jit_putobject(asm, cst_val);
Some(KeepCompiling)
}

fn gen_putobject(
jit: &mut JITState,
asm: &mut Assembler,
_ocb: &mut OutlinedCb,
ocb: &mut OutlinedCb,
) -> Option<CodegenStatus> {
let arg: VALUE = jit.get_arg(0);

if let Some(result) = fuse_putobject_opt_ltlt(jit, asm, arg, ocb) {
return Some(result);
}

jit_putobject(asm, arg);
Some(KeepCompiling)
}

/// Combine `putobject` and and `opt_ltlt` together if profitable, for example when
/// left shifting an integer by a constant amount.
fn fuse_putobject_opt_ltlt(
jit: &mut JITState,
asm: &mut Assembler,
constant_object: VALUE,
ocb: &mut OutlinedCb,
) -> Option<CodegenStatus> {
let next_opcode = unsafe { rb_vm_insn_addr2opcode(jit.pc.add(insn_len(jit.opcode).as_usize()).read().as_ptr()) };
if next_opcode == YARVINSN_opt_ltlt as i32 && constant_object.fixnum_p() {
// Untag the fixnum shift amount
let shift_amt = constant_object.as_isize() >> 1;
if shift_amt > 63 || shift_amt < 0 {
return None;
}
if !jit.at_current_insn() {
defer_compilation(jit, asm, ocb);
return Some(EndBlock);
}

let lhs = jit.peek_at_stack(&asm.ctx, 0);
if !lhs.fixnum_p() {
return None;
}

if !assume_bop_not_redefined(jit, asm, ocb, INTEGER_REDEFINED_OP_FLAG, BOP_LTLT) {
return None;
}

asm_comment!(asm, "integer left shift with rhs={shift_amt}");
let lhs = asm.stack_opnd(0);

// Guard that lhs is a fixnum if necessary
let lhs_type = asm.ctx.get_opnd_type(lhs.into());
if lhs_type != Type::Fixnum {
asm_comment!(asm, "guard arg0 fixnum");
asm.test(lhs, Opnd::UImm(RUBY_FIXNUM_FLAG as u64));

jit_chain_guard(
JCC_JZ,
jit,
asm,
ocb,
SEND_MAX_DEPTH,
Counter::guard_send_not_fixnums,
);
}

asm.stack_pop(1);
fixnum_left_shift_body(asm, lhs, shift_amt as u64);
return Some(SkipNextInsn);
}
return None;
}

fn gen_putself(
_jit: &mut JITState,
asm: &mut Assembler,
Expand Down Expand Up @@ -5073,8 +5145,13 @@ fn jit_rb_int_lshift(
Counter::lshift_amount_changed,
);

fixnum_left_shift_body(asm, lhs, shift_amt as u64);
true
}

fn fixnum_left_shift_body(asm: &mut Assembler, lhs: Opnd, shift_amt: u64) {
let in_val = asm.sub(lhs, 1.into());
let shift_opnd = Opnd::UImm(shift_amt as u64);
let shift_opnd = Opnd::UImm(shift_amt);
let out_val = asm.lshift(in_val, shift_opnd);
let unshifted = asm.rshift(out_val, shift_opnd);

Expand All @@ -5087,7 +5164,6 @@ fn jit_rb_int_lshift(

let ret_opnd = asm.stack_push(Type::Fixnum);
asm.mov(ret_opnd, out_val);
true
}

fn jit_rb_int_rshift(
Expand Down Expand Up @@ -10384,57 +10460,6 @@ mod tests {
assert!(cb.get_write_pos() > 0);
}

#[test]
fn test_putobject_qtrue() {
// Test gen_putobject with Qtrue
let (mut jit, _context, mut asm, mut cb, mut ocb) = setup_codegen();

let mut value_array: [u64; 2] = [0, Qtrue.into()];
let pc: *mut VALUE = &mut value_array as *mut u64 as *mut VALUE;
jit.pc = pc;

let status = gen_putobject(&mut jit, &mut asm, &mut ocb);

let tmp_type_top = asm.ctx.get_opnd_type(StackOpnd(0));

assert_eq!(status, Some(KeepCompiling));
assert_eq!(tmp_type_top, Type::True);
asm.compile(&mut cb, None).unwrap();
assert!(cb.get_write_pos() > 0);
}

#[test]
fn test_putobject_fixnum() {
// Test gen_putobject with a Fixnum to test another conditional branch
let (mut jit, _context, mut asm, mut cb, mut ocb) = setup_codegen();

// The Fixnum 7 is encoded as 7 * 2 + 1, or 15
let mut value_array: [u64; 2] = [0, 15];
let pc: *mut VALUE = &mut value_array as *mut u64 as *mut VALUE;
jit.pc = pc;

let status = gen_putobject(&mut jit, &mut asm, &mut ocb);

let tmp_type_top = asm.ctx.get_opnd_type(StackOpnd(0));

assert_eq!(status, Some(KeepCompiling));
assert_eq!(tmp_type_top, Type::Fixnum);
asm.compile(&mut cb, None).unwrap();
assert!(cb.get_write_pos() > 0);
}

#[test]
fn test_int2fix() {
let (mut jit, _context, mut asm, _cb, mut ocb) = setup_codegen();
jit.opcode = YARVINSN_putobject_INT2FIX_0_.as_usize();
let status = gen_putobject_int2fix(&mut jit, &mut asm, &mut ocb);

let tmp_type_top = asm.ctx.get_opnd_type(StackOpnd(0));

// Right now we're not testing the generated machine code to make sure a literal 1 or 0 was pushed. I've checked locally.
assert_eq!(status, Some(KeepCompiling));
assert_eq!(tmp_type_top, Type::Fixnum);
}

#[test]
fn test_putself() {
Expand Down