diff options
7 files changed, 71 insertions, 90 deletions
diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs index da6ccf21144..2767fe30c6f 100644 --- a/compiler/rustc_mir_transform/src/const_prop.rs +++ b/compiler/rustc_mir_transform/src/const_prop.rs @@ -14,8 +14,7 @@ use rustc_middle::mir::visit::{ }; use rustc_middle::mir::*; use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout}; -use rustc_middle::ty::GenericArgs; -use rustc_middle::ty::{self, ConstKind, Instance, ParamEnv, Ty, TyCtxt, TypeVisitableExt}; +use rustc_middle::ty::{self, GenericArgs, Instance, ParamEnv, Ty, TyCtxt, TypeVisitableExt}; use rustc_span::{def_id::DefId, Span, DUMMY_SP}; use rustc_target::abi::{self, Align, HasDataLayout, Size, TargetDataLayout}; use rustc_target::spec::abi::Abi as CallAbi; @@ -434,24 +433,8 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { } fn propagate_operand(&mut self, operand: &mut Operand<'tcx>) { - match *operand { - Operand::Copy(l) | Operand::Move(l) => { - if let Some(value) = self.get_const(l) && self.should_const_prop(&value) { - // FIXME(felix91gr): this code only handles `Scalar` cases. - // For now, we're not handling `ScalarPair` cases because - // doing so here would require a lot of code duplication. - // We should hopefully generalize `Operand` handling into a fn, - // and use it to do const-prop here and everywhere else - // where it makes sense. - if let interpret::Operand::Immediate(interpret::Immediate::Scalar( - scalar, - )) = *value - { - *operand = self.operand_from_scalar(scalar, value.layout.ty); - } - } - } - Operand::Constant(_) => (), + if let Some(place) = operand.place() && let Some(op) = self.replace_with_const(place) { + *operand = op; } } @@ -579,78 +562,63 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { })) } - fn replace_with_const(&mut self, place: Place<'tcx>, rval: &mut Rvalue<'tcx>) { + fn replace_with_const(&mut self, place: Place<'tcx>) -> Option<Operand<'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). - let Some(ref value) = self.get_const(place) else { return }; - if !self.should_const_prop(value) { - return; - } - trace!("replacing {:?}={:?} with {:?}", place, rval, value); - - if let Rvalue::Use(Operand::Constant(c)) = rval { - match c.literal { - ConstantKind::Ty(c) if matches!(c.kind(), ConstKind::Unevaluated(..)) => {} - _ => { - trace!("skipping replace of Rvalue::Use({:?} because it is already a const", c); - return; - } - } + let value = self.get_const(place)?; + if !self.should_const_prop(&value) { + return None; } + trace!("replacing {:?} with {:?}", place, value); - trace!("attempting to replace {:?} with {:?}", rval, value); // FIXME> figure out what to do when read_immediate_raw fails - let imm = self.ecx.read_immediate_raw(value).ok(); + let imm = self.ecx.read_immediate_raw(&value).ok()?; - if let Some(Right(imm)) = imm { - match *imm { - interpret::Immediate::Scalar(scalar) => { - *rval = Rvalue::Use(self.operand_from_scalar(scalar, value.layout.ty)); - } - Immediate::ScalarPair(..) => { - // Found a value represented as a pair. For now only do const-prop if the type - // of `rvalue` is also a tuple with two scalars. - // FIXME: enable the general case stated above ^. - let ty = value.layout.ty; - // Only do it for tuples - 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 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 }; - let literal = ConstantKind::Val(const_val, ty); - *rval = Rvalue::Use(Operand::Constant(Box::new(Constant { - span: DUMMY_SP, - user_ty: None, - literal, - }))); - } - } - } + let Right(imm) = imm else { return None }; + match *imm { + interpret::Immediate::Scalar(scalar) => { + Some(self.operand_from_scalar(scalar, value.layout.ty)) + } + Immediate::ScalarPair(..) => { + // Found a value represented as a pair. For now only do const-prop if the type + // of `rvalue` is also a tuple with two scalars. + // FIXME: enable the general case stated above ^. + let ty = value.layout.ty; + // Only do it for tuples + let ty::Tuple(types) = ty.kind() else { return None }; + // Only do it if tuple is also a pair with two scalars + if let [ty1, ty2] = types[..] { + 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) { + self.ecx + .intern_with_temp_alloc(value.layout, |ecx, dest| { + ecx.write_immediate(*imm, dest) + }) + .unwrap() + } else { + return None; + }; + + // 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 }; + let literal = ConstantKind::Val(const_val, ty); + Some(Operand::Constant(Box::new(Constant { + span: DUMMY_SP, + user_ty: None, + literal, + }))) + } else { + None } - // Scalars or scalar pairs that contain undef values are assumed to not have - // successfully evaluated and are thus not propagated. - _ => {} } + // Scalars or scalar pairs that contain undef values are assumed to not have + // successfully evaluated and are thus not propagated. + _ => None, } } @@ -847,7 +815,14 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> { ConstPropMode::NoPropagation => self.ensure_not_propagated(place.local), ConstPropMode::OnlyInsideOwnBlock | ConstPropMode::FullConstProp => { if let Some(()) = self.eval_rvalue_with_identities(rvalue, *place) { - self.replace_with_const(*place, rvalue); + // If this was already an evaluated constant, keep it. + if let Rvalue::Use(Operand::Constant(c)) = rvalue + && let ConstantKind::Val(..) = c.literal + { + 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); + } } else { // Const prop failed, so erase the destination, ensuring that whatever happens // from here on, does not know about the previous value. diff --git a/tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.panic-abort.diff b/tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.panic-abort.diff index e77c09848b7..ba2e89f0a74 100644 --- a/tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.panic-abort.diff +++ b/tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.panic-abort.diff @@ -8,8 +8,9 @@ bb0: { StorageLive(_1); - _1 = const _; +- _1 = const _; - switchInt(move _1) -> [0: bb2, otherwise: bb1]; ++ _1 = const false; + switchInt(const false) -> [0: bb2, otherwise: bb1]; } diff --git a/tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.panic-unwind.diff b/tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.panic-unwind.diff index 7496d254309..e0a610f60a7 100644 --- a/tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.panic-unwind.diff +++ b/tests/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.panic-unwind.diff @@ -8,8 +8,9 @@ bb0: { StorageLive(_1); - _1 = const _; +- _1 = const _; - switchInt(move _1) -> [0: bb2, otherwise: bb1]; ++ _1 = const false; + switchInt(const false) -> [0: bb2, otherwise: bb1]; } diff --git a/tests/mir-opt/const_prop/issue_67019.main.ConstProp.panic-abort.diff b/tests/mir-opt/const_prop/issue_67019.main.ConstProp.panic-abort.diff index 96b4093726c..0b03f3f71d3 100644 --- a/tests/mir-opt/const_prop/issue_67019.main.ConstProp.panic-abort.diff +++ b/tests/mir-opt/const_prop/issue_67019.main.ConstProp.panic-abort.diff @@ -11,8 +11,9 @@ StorageLive(_2); StorageLive(_3); - _3 = (const 1_u8, const 2_u8); +- _2 = (move _3,); + _3 = const (1_u8, 2_u8); - _2 = (move _3,); ++ _2 = (const (1_u8, 2_u8),); StorageDead(_3); _1 = test(move _2) -> [return: bb1, unwind unreachable]; } diff --git a/tests/mir-opt/const_prop/issue_67019.main.ConstProp.panic-unwind.diff b/tests/mir-opt/const_prop/issue_67019.main.ConstProp.panic-unwind.diff index 95776030162..97215425ee6 100644 --- a/tests/mir-opt/const_prop/issue_67019.main.ConstProp.panic-unwind.diff +++ b/tests/mir-opt/const_prop/issue_67019.main.ConstProp.panic-unwind.diff @@ -11,8 +11,9 @@ StorageLive(_2); StorageLive(_3); - _3 = (const 1_u8, const 2_u8); +- _2 = (move _3,); + _3 = const (1_u8, 2_u8); - _2 = (move _3,); ++ _2 = (const (1_u8, 2_u8),); StorageDead(_3); _1 = test(move _2) -> [return: bb1, unwind continue]; } diff --git a/tests/mir-opt/const_prop/tuple_literal_propagation.main.ConstProp.panic-abort.diff b/tests/mir-opt/const_prop/tuple_literal_propagation.main.ConstProp.panic-abort.diff index a72f24152fb..9e705695ac0 100644 --- a/tests/mir-opt/const_prop/tuple_literal_propagation.main.ConstProp.panic-abort.diff +++ b/tests/mir-opt/const_prop/tuple_literal_propagation.main.ConstProp.panic-abort.diff @@ -17,8 +17,9 @@ StorageLive(_2); StorageLive(_3); - _3 = _1; +- _2 = consume(move _3) -> [return: bb1, unwind unreachable]; + _3 = const (1_u32, 2_u32); - _2 = consume(move _3) -> [return: bb1, unwind unreachable]; ++ _2 = consume(const (1_u32, 2_u32)) -> [return: bb1, unwind unreachable]; } bb1: { diff --git a/tests/mir-opt/const_prop/tuple_literal_propagation.main.ConstProp.panic-unwind.diff b/tests/mir-opt/const_prop/tuple_literal_propagation.main.ConstProp.panic-unwind.diff index 6255f9ec596..882dd97cc16 100644 --- a/tests/mir-opt/const_prop/tuple_literal_propagation.main.ConstProp.panic-unwind.diff +++ b/tests/mir-opt/const_prop/tuple_literal_propagation.main.ConstProp.panic-unwind.diff @@ -17,8 +17,9 @@ StorageLive(_2); StorageLive(_3); - _3 = _1; +- _2 = consume(move _3) -> [return: bb1, unwind continue]; + _3 = const (1_u32, 2_u32); - _2 = consume(move _3) -> [return: bb1, unwind continue]; ++ _2 = consume(const (1_u32, 2_u32)) -> [return: bb1, unwind continue]; } bb1: { |