bjoernager/rust
bjoernager/rust
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Leave FIXME for wasm layout difference.

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There is a distinction between running this on wasm and i686, even though they should be
identical. This technically is not _incorrect_, it's just an unexpected difference, which is
worth investigating, but not for correctness.
This commit is contained in:
kadmin 2022-06-24 08:48:07 +00:00
parent 610e1a1e05
commit 15f4eec7a9
11 changed files with 297 additions and 315 deletions
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42
compiler/rustc_mir_transform/src/large_enums.rs
View file

@ -1,6 +1,6 @@
use crate::rustc_middle::ty::util::IntTypeExt;
use crate::MirPass;
use rustc_data_structures::stable_map::FxHashMap;
use rustc_data_structures::fx::FxHashMap;
use rustc_middle::mir::interpret::AllocId;
use rustc_middle::mir::*;
use rustc_middle::ty::{self, AdtDef, Const, ParamEnv, Ty, TyCtxt};
@ -19,6 +19,10 @@ use rustc_target::abi::{HasDataLayout, Size, TagEncoding, Variants};
/// Instead of emitting moves of the large variant,
/// Perform a memcpy instead.
/// Based off of [this HackMD](https://hackmd.io/@ft4bxUsFT5CEUBmRKYHr7w/rJM8BBPzD).
///
/// In summary, what this does is at runtime determine which enum variant is active,
/// and instead of copying all the bytes of the largest possible variant,
/// copy only the bytes for the currently active variant.
pub struct EnumSizeOpt {
pub(crate) discrepancy: u64,
}
@ -26,7 +30,10 @@ pub struct EnumSizeOpt {
impl<'tcx> MirPass<'tcx> for EnumSizeOpt {
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let sess = tcx.sess;
if (!sess.opts.debugging_opts.unsound_mir_opts) || sess.mir_opt_level() < 3 {
// FIXME(julianknodt): one thing noticed while testing this mir-opt is that there is a
// different layout of large enums on wasm. It's not clear what is causing this layout
// difference, as it should be identical to i686 (32 bit).
if (!sess.opts.unstable_opts.unsound_mir_opts) || sess.mir_opt_level() < 3 {
return;
}
self.optim(tcx, body);
@ -56,8 +63,8 @@ impl EnumSizeOpt {
Variants::Multiple { variants, .. } if variants.len() <= 1 => return None,
Variants::Multiple { variants, .. } => variants,
};
let min = variants.iter().map(|v| v.size()).min().unwrap();
let max = variants.iter().map(|v| v.size()).max().unwrap();
let min = variants.iter().map(|v| v.size).min().unwrap();
let max = variants.iter().map(|v| v.size).max().unwrap();
if max.bytes() - min.bytes() < self.discrepancy {
return None;
}
@ -92,7 +99,7 @@ impl EnumSizeOpt {
for (var_idx, layout) in variants.iter_enumerated() {
let curr_idx =
target_bytes * adt_def.discriminant_for_variant(tcx, var_idx).val as usize;
let sz = layout.size();
let sz = layout.size;
match ptr_sized_int {
rustc_target::abi::Integer::I32 => {
encode_store!(curr_idx, data_layout.endian, sz.bytes() as u32);
@ -115,8 +122,11 @@ impl EnumSizeOpt {
let mut alloc_cache = FxHashMap::default();
let body_did = body.source.def_id();
let param_env = tcx.param_env(body_did);
let (bbs, local_decls) = body.basic_blocks_and_local_decls_mut();
for bb in bbs {
let blocks = body.basic_blocks.as_mut();
let local_decls = &mut body.local_decls;
for bb in blocks {
bb.expand_statements(|st| {
if let StatementKind::Assign(box (
lhs,
@ -175,7 +185,7 @@ impl EnumSizeOpt {
kind: StatementKind::Assign(box (
discr_cast_place,
Rvalue::Cast(
CastKind::Misc,
CastKind::IntToInt,
Operand::Copy(discr_place),
tcx.types.usize,
),
@ -217,7 +227,7 @@ impl EnumSizeOpt {
source_info,
kind: StatementKind::Assign(box (
dst_cast_place,
Rvalue::Cast(CastKind::Misc, Operand::Copy(dst), dst_cast_ty),
Rvalue::Cast(CastKind::PtrToPtr, Operand::Copy(dst), dst_cast_ty),
)),
};
@ -240,17 +250,19 @@ impl EnumSizeOpt {
source_info,
kind: StatementKind::Assign(box (
src_cast_place,
Rvalue::Cast(CastKind::Misc, Operand::Copy(src), src_cast_ty),
Rvalue::Cast(CastKind::PtrToPtr, Operand::Copy(src), src_cast_ty),
)),
};
let copy_bytes = Statement {
source_info,
kind: StatementKind::CopyNonOverlapping(box CopyNonOverlapping {
src: Operand::Copy(src_cast_place),
dst: Operand::Copy(dst_cast_place),
count: Operand::Copy(size_place),
}),
kind: StatementKind::Intrinsic(
box NonDivergingIntrinsic::CopyNonOverlapping(CopyNonOverlapping {
src: Operand::Copy(src_cast_place),
dst: Operand::Copy(dst_cast_place),
count: Operand::Copy(size_place),
}),
),
};
let store_dead = Statement {

2
compiler/rustc_mir_transform/src/lib.rs
View file

@ -1,8 +1,8 @@
#![allow(rustc::potential_query_instability)]
#![feature(box_patterns)]
#![feature(drain_filter)]
#![feature(box_syntax)]
#![feature(let_chains)]
#![feature(let_else)]
#![feature(map_try_insert)]
#![feature(min_specialization)]
#![feature(never_type)]