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Fix Switch for 128bit integers

pull/1939/head
bjorn3 4 years ago
parent
c91a9313b5
commit
88a84e90ef
1 changed files with 97 additions and 16 deletions
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  1. 113
      cranelift/frontend/src/switch.rs

113
cranelift/frontend/src/switch.rs
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@ -1,11 +1,12 @@
use super::HashMap;
use crate::frontend::FunctionBuilder;
use alloc::vec::Vec;
use core::convert::TryFrom;
use cranelift_codegen::ir::condcodes::IntCC;
use cranelift_codegen::ir::*;
use log::debug;
type EntryIndex = u64;
type EntryIndex = u128;
/// Unlike with `br_table`, `Switch` cases may be sparse or non-0-based.
/// They emit efficient code using branches, jump tables, or a combination of both.
@ -152,11 +153,9 @@ impl Switch {
let left_block = bx.create_block();
let right_block = bx.create_block();
let should_take_right_side = bx.ins().icmp_imm(
IntCC::UnsignedGreaterThanOrEqual,
val,
right[0].first_index as i64,
);
let first_index = right[0].first_index;
let should_take_right_side =
icmp_imm_u128(bx, IntCC::UnsignedGreaterThanOrEqual, val, first_index);
bx.ins().brnz(should_take_right_side, right_block, &[]);
bx.ins().jump(left_block, &[]);
@ -200,7 +199,7 @@ impl Switch {
}
(1, _) => {
ins_fallthrough_jump(was_branch, bx);
let is_good_val = bx.ins().icmp_imm(IntCC::Equal, val, first_index as i64);
let is_good_val = icmp_imm_u128(bx, IntCC::Equal, val, first_index);
bx.ins().brnz(is_good_val, blocks[0], &[]);
}
(_, 0) => {
@ -217,11 +216,8 @@ impl Switch {
(_, _) => {
ins_fallthrough_jump(was_branch, bx);
let jt_block = bx.create_block();
let is_good_val = bx.ins().icmp_imm(
IntCC::UnsignedGreaterThanOrEqual,
val,
first_index as i64,
);
let is_good_val =
icmp_imm_u128(bx, IntCC::UnsignedGreaterThanOrEqual, val, first_index);
bx.ins().brnz(is_good_val, jt_block, &[]);
bx.seal_block(jt_block);
cases_and_jt_blocks.push((first_index, jt_block, blocks));
@ -241,6 +237,13 @@ impl Switch {
cases_and_jt_blocks: Vec<(EntryIndex, Block, Vec<Block>)>,
) {
for (first_index, jt_block, blocks) in cases_and_jt_blocks.into_iter().rev() {
// There are currently no 128bit systems supported by rustc, but once we do ensure that
// we don't silently ignore a part of the jump table for 128bit integers on 128bit systems.
assert!(
u64::try_from(blocks.len()).is_ok(),
"Jump tables bigger than 2^64-1 are not yet supported"
);
let mut jt_data = JumpTableData::new();
for block in blocks {
jt_data.push_entry(block);
@ -251,8 +254,33 @@ impl Switch {
let discr = if first_index == 0 {
val
} else {
bx.ins().iadd_imm(val, (first_index as i64).wrapping_neg())
if let Ok(first_index) = u64::try_from(first_index) {
bx.ins().iadd_imm(val, (first_index as i64).wrapping_neg())
} else {
let (lsb, msb) = (first_index as u64, (first_index >> 64) as u64);
let lsb = bx.ins().iconst(types::I64, lsb as i64);
let msb = bx.ins().iconst(types::I64, msb as i64);
let index = bx.ins().iconcat(lsb, msb);
bx.ins().isub(val, index)
}
};
let discr = if bx.func.dfg.value_type(discr).bits() > 64 {
// Check for overflow of cast to u64.
let new_block = bx.create_block();
let bigger_than_u64 =
bx.ins()
.icmp_imm(IntCC::UnsignedGreaterThan, discr, u64::max_value() as i64);
bx.ins().brnz(bigger_than_u64, otherwise, &[]);
bx.ins().jump(new_block, &[]);
bx.switch_to_block(new_block);
// Cast to u64, as br_table is not implemented for integers bigger than 64bits.
bx.ins().ireduce(types::I64, discr)
} else {
discr
};
bx.ins().br_table(discr, otherwise, jump_table);
}
}
@ -278,6 +306,18 @@ impl Switch {
}
}
fn icmp_imm_u128(bx: &mut FunctionBuilder, cond: IntCC, x: Value, y: u128) -> Value {
if let Ok(index) = u64::try_from(y) {
bx.ins().icmp_imm(cond, x, index as i64)
} else {
let (lsb, msb) = (y as u64, (y >> 64) as u64);
let lsb = bx.ins().iconst(types::I64, lsb as i64);
let msb = bx.ins().iconst(types::I64, msb as i64);
let index = bx.ins().iconcat(lsb, msb);
bx.ins().icmp(cond, x, index)
}
}
/// This represents a contiguous range of cases to switch on.
///
/// For example 10 => block1, 11 => block2, 12 => block7 will be represented as:
@ -440,7 +480,7 @@ block10:
#[test]
fn switch_min_index_value() {
let func = setup!(0, [::core::i64::MIN as u64, 1,]);
let func = setup!(0, [::core::i64::MIN as u64 as u128, 1,]);
assert_eq!(
func,
"block0:
@ -459,7 +499,7 @@ block3:
#[test]
fn switch_max_index_value() {
let func = setup!(0, [::core::i64::MAX as u64, 1,]);
let func = setup!(0, [::core::i64::MAX as u64 as u128, 1,]);
assert_eq!(
func,
"block0:
@ -478,7 +518,7 @@ block3:
#[test]
fn switch_optimal_codegen() {
let func = setup!(0, [-1i64 as u64, 0, 1,]);
let func = setup!(0, [-1i64 as u64 as u128, 0, 1,]);
assert_eq!(
func,
" jt0 = jump_table [block2, block3]
@ -530,4 +570,45 @@ block4:
builder.finalize(); // Will panic if some blocks are not sealed
}
#[test]
fn switch_128bit() {
let mut func = Function::new();
let mut func_ctx = FunctionBuilderContext::new();
{
let mut bx = FunctionBuilder::new(&mut func, &mut func_ctx);
let block0 = bx.create_block();
bx.switch_to_block(block0);
let val = bx.ins().iconst(types::I128, 0);
let mut switch = Switch::new();
let block1 = bx.create_block();
switch.set_entry(1, block1);
let block2 = bx.create_block();
switch.set_entry(0, block2);
let block3 = bx.create_block();
switch.emit(&mut bx, val, block3);
}
let func = func
.to_string()
.trim_start_matches("function u0:0() fast {\n")
.trim_end_matches("\n}\n")
.to_string();
assert_eq!(
func,
" jt0 = jump_table [block2, block1]
block0:
v0 = iconst.i128 0
jump block4
block4:
v1 = icmp_imm.i128 ugt v0, -1
brnz v1, block3
jump block5
block5:
v2 = ireduce.i64 v0
br_table v2, block3, jt0"
);
}
}

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