use rustc_abi::ExternAbi;
use rustc_ast::attr;
use rustc_hir::LangItem;
use rustc_middle::bug;
use rustc_middle::mir::*;
use rustc_middle::ty::layout::ValidityRequirement;
use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, layout};
use rustc_span::symbol::Symbol;
use rustc_span::{DUMMY_SP, sym};
use crate::simplify::simplify_duplicate_switch_targets;
use crate::take_array;
pub(super) enum InstSimplify {
BeforeInline,
AfterSimplifyCfg,
}
impl<'tcx> crate::MirPass<'tcx> for InstSimplify {
fn name(&self) -> &'static str {
match self {
InstSimplify::BeforeInline => "InstSimplify-before-inline",
InstSimplify::AfterSimplifyCfg => "InstSimplify-after-simplifycfg",
}
}
fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
sess.mir_opt_level() > 0
}
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let ctx = InstSimplifyContext {
tcx,
local_decls: &body.local_decls,
typing_env: body.typing_env(tcx),
};
let preserve_ub_checks =
attr::contains_name(tcx.hir().krate_attrs(), sym::rustc_preserve_ub_checks);
for block in body.basic_blocks.as_mut() {
for statement in block.statements.iter_mut() {
match statement.kind {
StatementKind::Assign(box (_place, ref mut rvalue)) => {
if !preserve_ub_checks {
ctx.simplify_ub_check(rvalue);
}
ctx.simplify_bool_cmp(rvalue);
ctx.simplify_ref_deref(rvalue);
ctx.simplify_len(rvalue);
ctx.simplify_ptr_aggregate(rvalue);
ctx.simplify_cast(rvalue);
}
_ => {}
}
}
ctx.simplify_primitive_clone(block.terminator.as_mut().unwrap(), &mut block.statements);
ctx.simplify_intrinsic_assert(block.terminator.as_mut().unwrap());
ctx.simplify_nounwind_call(block.terminator.as_mut().unwrap());
simplify_duplicate_switch_targets(block.terminator.as_mut().unwrap());
}
}
}
struct InstSimplifyContext<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
local_decls: &'a LocalDecls<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
}
impl<'tcx> InstSimplifyContext<'_, 'tcx> {
fn simplify_bool_cmp(&self, rvalue: &mut Rvalue<'tcx>) {
match rvalue {
Rvalue::BinaryOp(op @ (BinOp::Eq | BinOp::Ne), box (a, b)) => {
let new = match (op, self.try_eval_bool(a), self.try_eval_bool(b)) {
(BinOp::Eq, _, Some(true)) => Some(Rvalue::Use(a.clone())),
(BinOp::Ne, _, Some(false)) => Some(Rvalue::Use(a.clone())),
(BinOp::Eq, Some(true), _) => Some(Rvalue::Use(b.clone())),
(BinOp::Ne, Some(false), _) => Some(Rvalue::Use(b.clone())),
(BinOp::Eq, Some(false), _) => Some(Rvalue::UnaryOp(UnOp::Not, b.clone())),
(BinOp::Ne, Some(true), _) => Some(Rvalue::UnaryOp(UnOp::Not, b.clone())),
(BinOp::Eq, _, Some(false)) => Some(Rvalue::UnaryOp(UnOp::Not, a.clone())),
(BinOp::Ne, _, Some(true)) => Some(Rvalue::UnaryOp(UnOp::Not, a.clone())),
_ => None,
};
if let Some(new) = new {
*rvalue = new;
}
}
_ => {}
}
}
fn try_eval_bool(&self, a: &Operand<'_>) -> Option<bool> {
let a = a.constant()?;
if a.const_.ty().is_bool() { a.const_.try_to_bool() } else { None }
}
fn simplify_ref_deref(&self, rvalue: &mut Rvalue<'tcx>) {
if let Rvalue::Ref(_, _, place) | Rvalue::RawPtr(_, place) = rvalue {
if let Some((base, ProjectionElem::Deref)) = place.as_ref().last_projection() {
if rvalue.ty(self.local_decls, self.tcx) != base.ty(self.local_decls, self.tcx).ty {
return;
}
*rvalue = Rvalue::Use(Operand::Copy(Place {
local: base.local,
projection: self.tcx.mk_place_elems(base.projection),
}));
}
}
}
fn simplify_len(&self, rvalue: &mut Rvalue<'tcx>) {
if let Rvalue::Len(ref place) = *rvalue {
let place_ty = place.ty(self.local_decls, self.tcx).ty;
if let ty::Array(_, len) = *place_ty.kind() {
let const_ = Const::from_ty_const(len, self.tcx.types.usize, self.tcx);
let constant = ConstOperand { span: DUMMY_SP, const_, user_ty: None };
*rvalue = Rvalue::Use(Operand::Constant(Box::new(constant)));
}
}
}
fn simplify_ptr_aggregate(&self, rvalue: &mut Rvalue<'tcx>) {
if let Rvalue::Aggregate(box AggregateKind::RawPtr(pointee_ty, mutability), fields) = rvalue
{
let meta_ty = fields.raw[1].ty(self.local_decls, self.tcx);
if meta_ty.is_unit() {
let mut fields = std::mem::take(fields);
let _meta = fields.pop().unwrap();
let data = fields.pop().unwrap();
let ptr_ty = Ty::new_ptr(self.tcx, *pointee_ty, *mutability);
*rvalue = Rvalue::Cast(CastKind::PtrToPtr, data, ptr_ty);
}
}
}
fn simplify_ub_check(&self, rvalue: &mut Rvalue<'tcx>) {
if let Rvalue::NullaryOp(NullOp::UbChecks, _) = *rvalue {
let const_ = Const::from_bool(self.tcx, self.tcx.sess.ub_checks());
let constant = ConstOperand { span: DUMMY_SP, const_, user_ty: None };
*rvalue = Rvalue::Use(Operand::Constant(Box::new(constant)));
}
}
fn simplify_cast(&self, rvalue: &mut Rvalue<'tcx>) {
if let Rvalue::Cast(kind, operand, cast_ty) = rvalue {
let operand_ty = operand.ty(self.local_decls, self.tcx);
if operand_ty == *cast_ty {
*rvalue = Rvalue::Use(operand.clone());
} else if *kind == CastKind::Transmute {
if let (ty::Int(int), ty::Uint(uint)) | (ty::Uint(uint), ty::Int(int)) =
(operand_ty.kind(), cast_ty.kind())
&& int.bit_width() == uint.bit_width()
{
*kind = CastKind::IntToInt;
return;
}
if let ty::Adt(adt_def, args) = operand_ty.kind()
&& adt_def.repr().transparent()
&& (adt_def.is_struct() || adt_def.is_union())
&& let Some(place) = operand.place()
{
let variant = adt_def.non_enum_variant();
for (i, field) in variant.fields.iter_enumerated() {
let field_ty = field.ty(self.tcx, args);
if field_ty == *cast_ty {
let place = place
.project_deeper(&[ProjectionElem::Field(i, *cast_ty)], self.tcx);
let operand = if operand.is_move() {
Operand::Move(place)
} else {
Operand::Copy(place)
};
*rvalue = Rvalue::Use(operand);
return;
}
}
}
}
}
}
fn simplify_primitive_clone(
&self,
terminator: &mut Terminator<'tcx>,
statements: &mut Vec<Statement<'tcx>>,
) {
let TerminatorKind::Call { func, args, destination, target, .. } = &mut terminator.kind
else {
return;
};
let [arg] = &args[..] else { return };
let Some(destination_block) = *target else { return };
let Some((fn_def_id, fn_args)) = func.const_fn_def() else { return };
if fn_args.len() != 1 {
return;
}
let arg_ty = arg.node.ty(self.local_decls, self.tcx);
let ty::Ref(_region, inner_ty, Mutability::Not) = *arg_ty.kind() else { return };
if !inner_ty.is_trivially_pure_clone_copy() {
return;
}
if !self.tcx.is_lang_item(fn_def_id, LangItem::CloneFn) {
return;
}
let Ok([arg]) = take_array(args) else { return };
let Some(arg_place) = arg.node.place() else { return };
statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::Use(Operand::Copy(
arg_place.project_deeper(&[ProjectionElem::Deref], self.tcx),
)),
))),
});
terminator.kind = TerminatorKind::Goto { target: destination_block };
}
fn simplify_nounwind_call(&self, terminator: &mut Terminator<'tcx>) {
let TerminatorKind::Call { func, unwind, .. } = &mut terminator.kind else {
return;
};
let Some((def_id, _)) = func.const_fn_def() else {
return;
};
let body_ty = self.tcx.type_of(def_id).skip_binder();
let body_abi = match body_ty.kind() {
ty::FnDef(..) => body_ty.fn_sig(self.tcx).abi(),
ty::Closure(..) => ExternAbi::RustCall,
ty::Coroutine(..) => ExternAbi::Rust,
_ => bug!("unexpected body ty: {:?}", body_ty),
};
if !layout::fn_can_unwind(self.tcx, Some(def_id), body_abi) {
*unwind = UnwindAction::Unreachable;
}
}
fn simplify_intrinsic_assert(&self, terminator: &mut Terminator<'tcx>) {
let TerminatorKind::Call { func, target, .. } = &mut terminator.kind else {
return;
};
let Some(target_block) = target else {
return;
};
let func_ty = func.ty(self.local_decls, self.tcx);
let Some((intrinsic_name, args)) = resolve_rust_intrinsic(self.tcx, func_ty) else {
return;
};
if args.is_empty() {
return;
}
let known_is_valid =
intrinsic_assert_panics(self.tcx, self.typing_env, args[0], intrinsic_name);
match known_is_valid {
None => {}
Some(true) => {
*target = None;
}
Some(false) => {
terminator.kind = TerminatorKind::Goto { target: *target_block };
}
}
}
}
fn intrinsic_assert_panics<'tcx>(
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
arg: ty::GenericArg<'tcx>,
intrinsic_name: Symbol,
) -> Option<bool> {
let requirement = ValidityRequirement::from_intrinsic(intrinsic_name)?;
let ty = arg.expect_ty();
Some(!tcx.check_validity_requirement((requirement, typing_env.as_query_input(ty))).ok()?)
}
fn resolve_rust_intrinsic<'tcx>(
tcx: TyCtxt<'tcx>,
func_ty: Ty<'tcx>,
) -> Option<(Symbol, GenericArgsRef<'tcx>)> {
if let ty::FnDef(def_id, args) = *func_ty.kind() {
let intrinsic = tcx.intrinsic(def_id)?;
return Some((intrinsic.name, args));
}
None
}