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Return a Result from the TargetIsa::encode() method.

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When an instruction can't be encoded, provide a viable legalization
action in the form of a Legalize enum.
This commit is contained in:
Jakob Stoklund Olesen
2016-11-03 18:59:32 -07:00
parent 9c02fe3553
commit e59b47c41a
4 changed files with 64 additions and 40 deletions
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21
lib/cretonne/src/isa/enc_tables.rs
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@@ -3,7 +3,7 @@
//! This module contains types and functions for working with the encoding tables generated by
//! `lib/cretonne/meta/gen_encoding.py`.
use ir::{Type, Opcode};
use isa::Encoding;
use isa::{Encoding, Legalize};
use constant_hash::{Table, probe};
/// Level 1 hash table entry.
@@ -83,16 +83,21 @@ pub fn lookup_enclist<OffT1, OffT2>(ctrl_typevar: Type,
opcode: Opcode,
level1_table: &[Level1Entry<OffT1>],
level2_table: &[Level2Entry<OffT2>])
-> Option<usize>
-> Result<usize, Legalize>
where OffT1: Into<u32> + Copy,
OffT2: Into<u32> + Copy
{
probe(level1_table, ctrl_typevar, ctrl_typevar.index()).and_then(|l1idx| {
let l1ent = &level1_table[l1idx];
let l2off = l1ent.offset.into() as usize;
let l2tab = &level2_table[l2off..l2off + (1 << l1ent.log2len)];
probe(l2tab, opcode, opcode as usize).map(|l2idx| l2tab[l2idx].offset.into() as usize)
})
// TODO: The choice of legalization actions here is naive. This needs to be configurable.
probe(level1_table, ctrl_typevar, ctrl_typevar.index())
.ok_or(Legalize::Narrow)
.and_then(|l1idx| {
let l1ent = &level1_table[l1idx];
let l2off = l1ent.offset.into() as usize;
let l2tab = &level2_table[l2off..l2off + (1 << l1ent.log2len)];
probe(l2tab, opcode, opcode as usize)
.map(|l2idx| l2tab[l2idx].offset.into() as usize)
.ok_or(Legalize::Expand)
})
}
/// Encoding list entry.