bjoernager/rust
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Reuse CollectAndPatch for normal ConstProp.

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This commit is contained in:
Camille GILLOT 2023-08-03 12:06:37 +00:00
parent 8a3a0dd64e
commit 32fe00ae85
2 changed files with 75 additions and 93 deletions
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86
compiler/rustc_mir_transform/src/const_prop.rs
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@ -15,10 +15,11 @@ use rustc_middle::mir::visit::{
use rustc_middle::mir::*;
use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
use rustc_middle::ty::{self, GenericArgs, Instance, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
use rustc_span::{def_id::DefId, Span, DUMMY_SP};
use rustc_span::{def_id::DefId, Span};
use rustc_target::abi::{self, Align, HasDataLayout, Size, TargetDataLayout};
use rustc_target::spec::abi::Abi as CallAbi;
use crate::dataflow_const_prop::Patch;
use crate::MirPass;
use rustc_const_eval::interpret::{
self, compile_time_machine, AllocId, ConstAllocation, ConstValue, FnArg, Frame, ImmTy,
@ -120,6 +121,8 @@ impl<'tcx> MirPass<'tcx> for ConstProp {
optimization_finder.visit_basic_block_data(bb, data);
}
optimization_finder.patch.visit_body_preserves_cfg(body);
trace!("ConstProp done for {:?}", def_id);
}
}
@ -302,6 +305,7 @@ struct ConstPropagator<'mir, 'tcx> {
tcx: TyCtxt<'tcx>,
param_env: ParamEnv<'tcx>,
local_decls: &'mir IndexSlice<Local, LocalDecl<'tcx>>,
patch: Patch<'tcx>,
}
impl<'tcx> LayoutOfHelpers<'tcx> for ConstPropagator<'_, 'tcx> {
@ -385,7 +389,8 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
ecx.frame_mut().locals[local].make_live_uninit();
}
ConstPropagator { ecx, tcx, param_env, local_decls: &dummy_body.local_decls }
let patch = Patch::new(tcx);
ConstPropagator { ecx, tcx, param_env, local_decls: &dummy_body.local_decls, patch }
}
fn get_const(&self, place: Place<'tcx>) -> Option<OpTy<'tcx>> {
@ -422,12 +427,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
ecx.machine.written_only_inside_own_block_locals.remove(&local);
}
fn propagate_operand(&mut self, operand: &mut Operand<'tcx>) {
if let Some(place) = operand.place() && let Some(op) = self.replace_with_const(place) {
*operand = op;
}
}
fn check_rvalue(&mut self, rvalue: &Rvalue<'tcx>) -> Option<()> {
// Perform any special handling for specific Rvalue types.
// Generally, checks here fall into one of two categories:
@ -543,16 +542,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
}
}
/// Creates a new `Operand::Constant` from a `Scalar` value
fn operand_from_scalar(&self, scalar: Scalar, ty: Ty<'tcx>) -> Operand<'tcx> {
Operand::Constant(Box::new(Constant {
span: DUMMY_SP,
user_ty: None,
literal: ConstantKind::from_scalar(self.tcx, scalar, ty),
}))
}
fn replace_with_const(&mut self, place: Place<'tcx>) -> Option<Operand<'tcx>> {
fn replace_with_const(&mut self, place: Place<'tcx>) -> Option<ConstantKind<'tcx>> {
// This will return None if the above `const_prop` invocation only "wrote" a
// type whose creation requires no write. E.g. a generator whose initial state
// consists solely of uninitialized memory (so it doesn't capture any locals).
@ -568,7 +558,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
let Right(imm) = imm else { return None };
match *imm {
Immediate::Scalar(scalar) if scalar.try_to_int().is_ok() => {
Some(self.operand_from_scalar(scalar, value.layout.ty))
Some(ConstantKind::from_scalar(self.tcx, scalar, value.layout.ty))
}
Immediate::ScalarPair(l, r) if l.try_to_int().is_ok() && r.try_to_int().is_ok() => {
let alloc = self
@ -578,15 +568,10 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
})
.ok()?;
let literal = ConstantKind::Val(
Some(ConstantKind::Val(
ConstValue::ByRef { alloc, offset: Size::ZERO },
value.layout.ty,
);
Some(Operand::Constant(Box::new(Constant {
span: DUMMY_SP,
user_ty: None,
literal,
})))
))
}
// Scalars or scalar pairs that contain undef values are assumed to not have
// successfully evaluated and are thus not propagated.
@ -728,40 +713,29 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
}
}
impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn visit_operand(&mut self, operand: &mut Operand<'tcx>, location: Location) {
impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) {
self.super_operand(operand, location);
self.propagate_operand(operand)
}
fn process_projection_elem(
&mut self,
elem: PlaceElem<'tcx>,
_: Location,
) -> Option<PlaceElem<'tcx>> {
if let PlaceElem::Index(local) = elem
&& let Some(value) = self.get_const(local.into())
&& let Some(imm) = value.as_mplace_or_imm().right()
&& let Immediate::Scalar(scalar) = *imm
&& let Ok(offset) = scalar.to_target_usize(&self.tcx)
&& let Some(min_length) = offset.checked_add(1)
{
Some(PlaceElem::ConstantIndex { offset, min_length, from_end: false })
} else {
None
if let Some(place) = operand.place() && let Some(value) = self.replace_with_const(place) {
self.patch.before_effect.insert((location, place), value);
}
}
fn visit_assign(
fn visit_projection_elem(
&mut self,
place: &mut Place<'tcx>,
rvalue: &mut Rvalue<'tcx>,
_: PlaceRef<'tcx>,
elem: PlaceElem<'tcx>,
_: PlaceContext,
location: Location,
) {
if let PlaceElem::Index(local) = elem
&& let Some(value) = self.replace_with_const(local.into())
{
self.patch.before_effect.insert((location, local.into()), value);
}
}
fn visit_assign(&mut self, place: &Place<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) {
self.super_assign(place, rvalue, location);
let Some(()) = self.check_rvalue(rvalue) else { return };
@ -778,7 +752,7 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
{
trace!("skipping replace of Rvalue::Use({:?} because it is already a const", c);
} else if let Some(operand) = self.replace_with_const(*place) {
*rvalue = Rvalue::Use(operand);
self.patch.assignments.insert(location, operand);
}
} else {
// Const prop failed, so erase the destination, ensuring that whatever happens
@ -802,7 +776,7 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
}
}
fn visit_statement(&mut self, statement: &mut Statement<'tcx>, location: Location) {
fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
trace!("visit_statement: {:?}", statement);
// We want to evaluate operands before any change to the assigned-to value,
@ -846,7 +820,7 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
}
}
fn visit_basic_block_data(&mut self, block: BasicBlock, data: &mut BasicBlockData<'tcx>) {
fn visit_basic_block_data(&mut self, block: BasicBlock, data: &BasicBlockData<'tcx>) {
self.super_basic_block_data(block, data);
// We remove all Locals which are restricted in propagation to their containing blocks and