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-rw-r--r--compiler/rustc_mir_transform/src/const_prop.rs351
1 files changed, 121 insertions, 230 deletions
diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index 5c45abc5a..6b2eefce2 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -5,7 +5,6 @@ use std::cell::Cell;
use either::Right;
-use rustc_ast::Mutability;
use rustc_const_eval::const_eval::CheckAlignment;
use rustc_data_structures::fx::FxHashSet;
use rustc_hir::def::DefKind;
@@ -14,14 +13,10 @@ use rustc_index::vec::IndexVec;
use rustc_middle::mir::visit::{
MutVisitor, MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor,
};
-use rustc_middle::mir::{
- BasicBlock, BinOp, Body, Constant, ConstantKind, Local, LocalDecl, LocalKind, Location,
- Operand, Place, Rvalue, SourceInfo, Statement, StatementKind, Terminator, TerminatorKind, UnOp,
- RETURN_PLACE,
-};
+use rustc_middle::mir::*;
use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
use rustc_middle::ty::InternalSubsts;
-use rustc_middle::ty::{self, ConstKind, Instance, ParamEnv, Ty, TyCtxt, TypeVisitable};
+use rustc_middle::ty::{self, ConstKind, Instance, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
use rustc_span::{def_id::DefId, Span};
use rustc_target::abi::{self, Align, HasDataLayout, Size, TargetDataLayout};
use rustc_target::spec::abi::Abi as CallAbi;
@@ -83,7 +78,7 @@ impl<'tcx> MirPass<'tcx> for ConstProp {
return;
}
- let is_generator = tcx.type_of(def_id.to_def_id()).is_generator();
+ let is_generator = tcx.type_of(def_id.to_def_id()).subst_identity().is_generator();
// FIXME(welseywiser) const prop doesn't work on generators because of query cycles
// computing their layout.
if is_generator {
@@ -289,7 +284,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx>
}
// If the static allocation is mutable, then we can't const prop it as its content
// might be different at runtime.
- if alloc.inner().mutability == Mutability::Mut {
+ if alloc.inner().mutability.is_mut() {
throw_machine_stop_str!("can't access mutable globals in ConstProp");
}
@@ -457,27 +452,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
};
}
- fn use_ecx<F, T>(&mut self, f: F) -> Option<T>
- where
- F: FnOnce(&mut Self) -> InterpResult<'tcx, T>,
- {
- match f(self) {
- Ok(val) => Some(val),
- Err(error) => {
- trace!("InterpCx operation failed: {:?}", error);
- // Some errors shouldn't come up because creating them causes
- // an allocation, which we should avoid. When that happens,
- // dedicated error variants should be introduced instead.
- assert!(
- !error.kind().formatted_string(),
- "const-prop encountered formatting error: {}",
- error
- );
- None
- }
- }
- }
-
/// Returns the value, if any, of evaluating `c`.
fn eval_constant(&mut self, c: &Constant<'tcx>) -> Option<OpTy<'tcx>> {
// FIXME we need to revisit this for #67176
@@ -492,7 +466,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
/// Returns the value, if any, of evaluating `place`.
fn eval_place(&mut self, place: Place<'tcx>) -> Option<OpTy<'tcx>> {
trace!("eval_place(place={:?})", place);
- self.use_ecx(|this| this.ecx.eval_place_to_op(place, None))
+ self.ecx.eval_place_to_op(place, None).ok()
}
/// Returns the value, if any, of evaluating `op`. Calls upon `eval_constant`
@@ -504,55 +478,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
}
}
- fn check_unary_op(&mut self, op: UnOp, arg: &Operand<'tcx>) -> Option<()> {
- if self.use_ecx(|this| {
- let val = this.ecx.read_immediate(&this.ecx.eval_operand(arg, None)?)?;
- let (_res, overflow, _ty) = this.ecx.overflowing_unary_op(op, &val)?;
- Ok(overflow)
- })? {
- // `AssertKind` only has an `OverflowNeg` variant, so make sure that is
- // appropriate to use.
- assert_eq!(op, UnOp::Neg, "Neg is the only UnOp that can overflow");
- return None;
- }
-
- Some(())
- }
-
- fn check_binary_op(
- &mut self,
- op: BinOp,
- left: &Operand<'tcx>,
- right: &Operand<'tcx>,
- ) -> Option<()> {
- let r = self.use_ecx(|this| this.ecx.read_immediate(&this.ecx.eval_operand(right, None)?));
- let l = self.use_ecx(|this| this.ecx.read_immediate(&this.ecx.eval_operand(left, None)?));
- // Check for exceeding shifts *even if* we cannot evaluate the LHS.
- if op == BinOp::Shr || op == BinOp::Shl {
- let r = r.clone()?;
- // We need the type of the LHS. We cannot use `place_layout` as that is the type
- // of the result, which for checked binops is not the same!
- let left_ty = left.ty(self.local_decls, self.tcx);
- let left_size = self.ecx.layout_of(left_ty).ok()?.size;
- let right_size = r.layout.size;
- let r_bits = r.to_scalar().to_bits(right_size).ok();
- if r_bits.map_or(false, |b| b >= left_size.bits() as u128) {
- return None;
- }
- }
-
- if let (Some(l), Some(r)) = (&l, &r) {
- // The remaining operators are handled through `overflowing_binary_op`.
- if self.use_ecx(|this| {
- let (_res, overflow, _ty) = this.ecx.overflowing_binary_op(op, l, r)?;
- Ok(overflow)
- })? {
- return None;
- }
- }
- Some(())
- }
-
fn propagate_operand(&mut self, operand: &mut Operand<'tcx>) {
match *operand {
Operand::Copy(l) | Operand::Move(l) => {
@@ -588,28 +513,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
// 2. Working around bugs in other parts of the compiler
// - In this case, we'll return `None` from this function to stop evaluation.
match rvalue {
- // Additional checking: give lints to the user if an overflow would occur.
- // We do this here and not in the `Assert` terminator as that terminator is
- // only sometimes emitted (overflow checks can be disabled), but we want to always
- // lint.
- Rvalue::UnaryOp(op, arg) => {
- trace!("checking UnaryOp(op = {:?}, arg = {:?})", op, arg);
- self.check_unary_op(*op, arg)?;
- }
- Rvalue::BinaryOp(op, box (left, right)) => {
- trace!("checking BinaryOp(op = {:?}, left = {:?}, right = {:?})", op, left, right);
- self.check_binary_op(*op, left, right)?;
- }
- Rvalue::CheckedBinaryOp(op, box (left, right)) => {
- trace!(
- "checking CheckedBinaryOp(op = {:?}, left = {:?}, right = {:?})",
- op,
- left,
- right
- );
- self.check_binary_op(*op, left, right)?;
- }
-
// Do not try creating references (#67862)
Rvalue::AddressOf(_, place) | Rvalue::Ref(_, _, place) => {
trace!("skipping AddressOf | Ref for {:?}", place);
@@ -639,7 +542,10 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
| Rvalue::Cast(..)
| Rvalue::ShallowInitBox(..)
| Rvalue::Discriminant(..)
- | Rvalue::NullaryOp(..) => {}
+ | Rvalue::NullaryOp(..)
+ | Rvalue::UnaryOp(..)
+ | Rvalue::BinaryOp(..)
+ | Rvalue::CheckedBinaryOp(..) => {}
}
// FIXME we need to revisit this for #67176
@@ -664,35 +570,37 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
rvalue: &Rvalue<'tcx>,
place: Place<'tcx>,
) -> Option<()> {
- self.use_ecx(|this| match rvalue {
+ match rvalue {
Rvalue::BinaryOp(op, box (left, right))
| Rvalue::CheckedBinaryOp(op, box (left, right)) => {
- let l = this.ecx.eval_operand(left, None).and_then(|x| this.ecx.read_immediate(&x));
+ let l = self.ecx.eval_operand(left, None).and_then(|x| self.ecx.read_immediate(&x));
let r =
- this.ecx.eval_operand(right, None).and_then(|x| this.ecx.read_immediate(&x));
+ self.ecx.eval_operand(right, None).and_then(|x| self.ecx.read_immediate(&x));
let const_arg = match (l, r) {
(Ok(x), Err(_)) | (Err(_), Ok(x)) => x, // exactly one side is known
- (Err(e), Err(_)) => return Err(e), // neither side is known
- (Ok(_), Ok(_)) => return this.ecx.eval_rvalue_into_place(rvalue, place), // both sides are known
+ (Err(_), Err(_)) => return None, // neither side is known
+ (Ok(_), Ok(_)) => return self.ecx.eval_rvalue_into_place(rvalue, place).ok(), // both sides are known
};
if !matches!(const_arg.layout.abi, abi::Abi::Scalar(..)) {
// We cannot handle Scalar Pair stuff.
// No point in calling `eval_rvalue_into_place`, since only one side is known
- throw_machine_stop_str!("cannot optimize this")
+ return None;
}
- let arg_value = const_arg.to_scalar().to_bits(const_arg.layout.size)?;
- let dest = this.ecx.eval_place(place)?;
+ let arg_value = const_arg.to_scalar().to_bits(const_arg.layout.size).ok()?;
+ let dest = self.ecx.eval_place(place).ok()?;
match op {
- BinOp::BitAnd if arg_value == 0 => this.ecx.write_immediate(*const_arg, &dest),
+ BinOp::BitAnd if arg_value == 0 => {
+ self.ecx.write_immediate(*const_arg, &dest).ok()
+ }
BinOp::BitOr
if arg_value == const_arg.layout.size.truncate(u128::MAX)
|| (const_arg.layout.ty.is_bool() && arg_value == 1) =>
{
- this.ecx.write_immediate(*const_arg, &dest)
+ self.ecx.write_immediate(*const_arg, &dest).ok()
}
BinOp::Mul if const_arg.layout.ty.is_integral() && arg_value == 0 => {
if let Rvalue::CheckedBinaryOp(_, _) = rvalue {
@@ -700,16 +608,16 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
const_arg.to_scalar(),
Scalar::from_bool(false),
);
- this.ecx.write_immediate(val, &dest)
+ self.ecx.write_immediate(val, &dest).ok()
} else {
- this.ecx.write_immediate(*const_arg, &dest)
+ self.ecx.write_immediate(*const_arg, &dest).ok()
}
}
- _ => throw_machine_stop_str!("cannot optimize this"),
+ _ => None,
}
}
- _ => this.ecx.eval_rvalue_into_place(rvalue, place),
- })
+ _ => self.ecx.eval_rvalue_into_place(rvalue, place).ok(),
+ }
}
/// Creates a new `Operand::Constant` from a `Scalar` value
@@ -751,7 +659,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
}
// FIXME> figure out what to do when read_immediate_raw fails
- let imm = self.use_ecx(|this| this.ecx.read_immediate_raw(value));
+ let imm = self.ecx.read_immediate_raw(value).ok();
if let Some(Right(imm)) = imm {
match *imm {
@@ -771,25 +679,23 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
if let ty::Tuple(types) = ty.kind() {
// Only do it if tuple is also a pair with two scalars
if let [ty1, ty2] = types[..] {
- let alloc = self.use_ecx(|this| {
- let ty_is_scalar = |ty| {
- this.ecx.layout_of(ty).ok().map(|layout| layout.abi.is_scalar())
- == Some(true)
- };
- if ty_is_scalar(ty1) && ty_is_scalar(ty2) {
- let alloc = this
- .ecx
- .intern_with_temp_alloc(value.layout, |ecx, dest| {
- ecx.write_immediate(*imm, dest)
- })
- .unwrap();
- Ok(Some(alloc))
- } else {
- Ok(None)
- }
- });
-
- if let Some(Some(alloc)) = alloc {
+ let ty_is_scalar = |ty| {
+ self.ecx.layout_of(ty).ok().map(|layout| layout.abi.is_scalar())
+ == Some(true)
+ };
+ let alloc = if ty_is_scalar(ty1) && ty_is_scalar(ty2) {
+ let alloc = self
+ .ecx
+ .intern_with_temp_alloc(value.layout, |ecx, dest| {
+ ecx.write_immediate(*imm, dest)
+ })
+ .unwrap();
+ Some(alloc)
+ } else {
+ None
+ };
+
+ if let Some(alloc) = alloc {
// Assign entire constant in a single statement.
// We can't use aggregates, as we run after the aggregate-lowering `MirPhase`.
let const_val = ConstValue::ByRef { alloc, offset: Size::ZERO };
@@ -990,84 +896,80 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
trace!("visit_statement: {:?}", statement);
let source_info = statement.source_info;
self.source_info = Some(source_info);
- if let StatementKind::Assign(box (place, ref mut rval)) = statement.kind {
- let can_const_prop = self.ecx.machine.can_const_prop[place.local];
- if let Some(()) = self.const_prop(rval, place) {
- // 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).
- if let Some(ref value) = self.get_const(place) && self.should_const_prop(value) {
- trace!("replacing {:?} with {:?}", rval, value);
- self.replace_with_const(rval, value, source_info);
- if can_const_prop == ConstPropMode::FullConstProp
- || can_const_prop == ConstPropMode::OnlyInsideOwnBlock
- {
- trace!("propagated into {:?}", place);
+ match statement.kind {
+ StatementKind::Assign(box (place, ref mut rval)) => {
+ let can_const_prop = self.ecx.machine.can_const_prop[place.local];
+ if let Some(()) = self.const_prop(rval, place) {
+ // 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).
+ if let Some(ref value) = self.get_const(place) && self.should_const_prop(value) {
+ trace!("replacing {:?} with {:?}", rval, value);
+ self.replace_with_const(rval, value, source_info);
+ if can_const_prop == ConstPropMode::FullConstProp
+ || can_const_prop == ConstPropMode::OnlyInsideOwnBlock
+ {
+ trace!("propagated into {:?}", place);
+ }
}
- }
- match can_const_prop {
- ConstPropMode::OnlyInsideOwnBlock => {
- trace!(
- "found local restricted to its block. \
+ match can_const_prop {
+ ConstPropMode::OnlyInsideOwnBlock => {
+ trace!(
+ "found local restricted to its block. \
Will remove it from const-prop after block is finished. Local: {:?}",
- place.local
- );
- }
- ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
- trace!("can't propagate into {:?}", place);
- if place.local != RETURN_PLACE {
- Self::remove_const(&mut self.ecx, place.local);
+ place.local
+ );
}
- }
- ConstPropMode::FullConstProp => {}
- }
- } else {
- // Const prop failed, so erase the destination, ensuring that whatever happens
- // from here on, does not know about the previous value.
- // This is important in case we have
- // ```rust
- // let mut x = 42;
- // x = SOME_MUTABLE_STATIC;
- // // x must now be uninit
- // ```
- // FIXME: we overzealously erase the entire local, because that's easier to
- // implement.
- trace!(
- "propagation into {:?} failed.
- Nuking the entire site from orbit, it's the only way to be sure",
- place,
- );
- Self::remove_const(&mut self.ecx, place.local);
- }
- } else {
- match statement.kind {
- StatementKind::SetDiscriminant { ref place, .. } => {
- match self.ecx.machine.can_const_prop[place.local] {
- ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => {
- if self.use_ecx(|this| this.ecx.statement(statement)).is_some() {
- trace!("propped discriminant into {:?}", place);
- } else {
+ ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
+ trace!("can't propagate into {:?}", place);
+ if place.local != RETURN_PLACE {
Self::remove_const(&mut self.ecx, place.local);
}
}
- ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
- Self::remove_const(&mut self.ecx, place.local);
- }
+ ConstPropMode::FullConstProp => {}
}
+ } else {
+ // Const prop failed, so erase the destination, ensuring that whatever happens
+ // from here on, does not know about the previous value.
+ // This is important in case we have
+ // ```rust
+ // let mut x = 42;
+ // x = SOME_MUTABLE_STATIC;
+ // // x must now be uninit
+ // ```
+ // FIXME: we overzealously erase the entire local, because that's easier to
+ // implement.
+ trace!(
+ "propagation into {:?} failed.
+ Nuking the entire site from orbit, it's the only way to be sure",
+ place,
+ );
+ Self::remove_const(&mut self.ecx, place.local);
}
- StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => {
- let frame = self.ecx.frame_mut();
- frame.locals[local].value =
- if let StatementKind::StorageLive(_) = statement.kind {
- LocalValue::Live(interpret::Operand::Immediate(
- interpret::Immediate::Uninit,
- ))
+ }
+ StatementKind::SetDiscriminant { ref place, .. } => {
+ match self.ecx.machine.can_const_prop[place.local] {
+ ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => {
+ if self.ecx.statement(statement).is_ok() {
+ trace!("propped discriminant into {:?}", place);
} else {
- LocalValue::Dead
- };
+ Self::remove_const(&mut self.ecx, place.local);
+ }
+ }
+ ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
+ Self::remove_const(&mut self.ecx, place.local);
+ }
}
- _ => {}
}
+ StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => {
+ let frame = self.ecx.frame_mut();
+ frame.locals[local].value = if let StatementKind::StorageLive(_) = statement.kind {
+ LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit))
+ } else {
+ LocalValue::Dead
+ };
+ }
+ _ => {}
}
self.super_statement(statement, location);
@@ -1077,34 +979,19 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
let source_info = terminator.source_info;
self.source_info = Some(source_info);
self.super_terminator(terminator, location);
- // Do NOT early return in this function, it does some crucial fixup of the state at the end!
+
match &mut terminator.kind {
TerminatorKind::Assert { expected, ref mut cond, .. } => {
- if let Some(ref value) = self.eval_operand(&cond) {
+ if let Some(ref value) = self.eval_operand(&cond)
+ && let Ok(value_const) = self.ecx.read_scalar(&value)
+ && self.should_const_prop(value)
+ {
trace!("assertion on {:?} should be {:?}", value, expected);
- let expected = Scalar::from_bool(*expected);
- // FIXME should be used use_ecx rather than a local match... but we have
- // quite a few of these read_scalar/read_immediate that need fixing.
- if let Ok(value_const) = self.ecx.read_scalar(&value) {
- if expected != value_const {
- // Poison all places this operand references so that further code
- // doesn't use the invalid value
- match cond {
- Operand::Move(ref place) | Operand::Copy(ref place) => {
- Self::remove_const(&mut self.ecx, place.local);
- }
- Operand::Constant(_) => {}
- }
- } else {
- if self.should_const_prop(value) {
- *cond = self.operand_from_scalar(
- value_const,
- self.tcx.types.bool,
- source_info.span,
- );
- }
- }
- }
+ *cond = self.operand_from_scalar(
+ value_const,
+ self.tcx.types.bool,
+ source_info.span,
+ );
}
}
TerminatorKind::SwitchInt { ref mut discr, .. } => {
@@ -1132,6 +1019,10 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
// gated on `mir_opt_level=3`.
TerminatorKind::Call { .. } => {}
}
+ }
+
+ fn visit_basic_block_data(&mut self, block: BasicBlock, data: &mut BasicBlockData<'tcx>) {
+ self.super_basic_block_data(block, data);
// We remove all Locals which are restricted in propagation to their containing blocks and
// which were modified in the current block.
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-21 09:51:58 +0000