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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:43 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:43 +0000 |
commit | 3e3e70d529d8c7d7c4d7bc4fefc9f109393b9245 (patch) | |
tree | daf049b282ab10e8c3d03e409b3cd84ff3f7690c /compiler/rustc_mir_transform/src/const_prop.rs | |
parent | Adding debian version 1.68.2+dfsg1-1. (diff) | |
download | rustc-3e3e70d529d8c7d7c4d7bc4fefc9f109393b9245.tar.xz rustc-3e3e70d529d8c7d7c4d7bc4fefc9f109393b9245.zip |
Merging upstream version 1.69.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'compiler/rustc_mir_transform/src/const_prop.rs')
-rw-r--r-- | compiler/rustc_mir_transform/src/const_prop.rs | 351 |
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. |