diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src/instsimplify.rs')
| -rw-r--r-- | compiler/rustc_mir_transform/src/instsimplify.rs | 217 |
1 files changed, 94 insertions, 123 deletions
diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs index 2eff6b31372..5f0c55ddc09 100644 --- a/compiler/rustc_mir_transform/src/instsimplify.rs +++ b/compiler/rustc_mir_transform/src/instsimplify.rs @@ -10,7 +10,6 @@ use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, layout}; use rustc_span::{DUMMY_SP, Symbol, sym}; use crate::simplify::simplify_duplicate_switch_targets; -use crate::take_array; pub(super) enum InstSimplify { BeforeInline, @@ -39,26 +38,26 @@ impl<'tcx> crate::MirPass<'tcx> for InstSimplify { 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_ptr_aggregate(rvalue); - ctx.simplify_cast(rvalue); - ctx.simplify_repeated_aggregate(rvalue); - ctx.simplify_repeat_once(rvalue); - } - _ => {} + let StatementKind::Assign(box (.., rvalue)) = &mut statement.kind else { + continue; + }; + + if !preserve_ub_checks { + ctx.simplify_ub_check(rvalue); } + ctx.simplify_bool_cmp(rvalue); + ctx.simplify_ref_deref(rvalue); + ctx.simplify_ptr_aggregate(rvalue); + ctx.simplify_cast(rvalue); + ctx.simplify_repeated_aggregate(rvalue); + ctx.simplify_repeat_once(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()); + let terminator = block.terminator.as_mut().unwrap(); + ctx.simplify_primitive_clone(terminator, &mut block.statements); + ctx.simplify_intrinsic_assert(terminator); + ctx.simplify_nounwind_call(terminator); + simplify_duplicate_switch_targets(terminator); } } @@ -105,43 +104,34 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { /// Transform boolean comparisons into logical operations. 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)) { - // Transform "Eq(a, true)" ==> "a" - (BinOp::Eq, _, Some(true)) => Some(Rvalue::Use(a.clone())), + let Rvalue::BinaryOp(op @ (BinOp::Eq | BinOp::Ne), box (a, b)) = &*rvalue else { return }; + *rvalue = match (op, self.try_eval_bool(a), self.try_eval_bool(b)) { + // Transform "Eq(a, true)" ==> "a" + (BinOp::Eq, _, Some(true)) => Rvalue::Use(a.clone()), - // Transform "Ne(a, false)" ==> "a" - (BinOp::Ne, _, Some(false)) => Some(Rvalue::Use(a.clone())), + // Transform "Ne(a, false)" ==> "a" + (BinOp::Ne, _, Some(false)) => Rvalue::Use(a.clone()), - // Transform "Eq(true, b)" ==> "b" - (BinOp::Eq, Some(true), _) => Some(Rvalue::Use(b.clone())), + // Transform "Eq(true, b)" ==> "b" + (BinOp::Eq, Some(true), _) => Rvalue::Use(b.clone()), - // Transform "Ne(false, b)" ==> "b" - (BinOp::Ne, Some(false), _) => Some(Rvalue::Use(b.clone())), + // Transform "Ne(false, b)" ==> "b" + (BinOp::Ne, Some(false), _) => Rvalue::Use(b.clone()), - // Transform "Eq(false, b)" ==> "Not(b)" - (BinOp::Eq, Some(false), _) => Some(Rvalue::UnaryOp(UnOp::Not, b.clone())), + // Transform "Eq(false, b)" ==> "Not(b)" + (BinOp::Eq, Some(false), _) => Rvalue::UnaryOp(UnOp::Not, b.clone()), - // Transform "Ne(true, b)" ==> "Not(b)" - (BinOp::Ne, Some(true), _) => Some(Rvalue::UnaryOp(UnOp::Not, b.clone())), + // Transform "Ne(true, b)" ==> "Not(b)" + (BinOp::Ne, Some(true), _) => Rvalue::UnaryOp(UnOp::Not, b.clone()), - // Transform "Eq(a, false)" ==> "Not(a)" - (BinOp::Eq, _, Some(false)) => Some(Rvalue::UnaryOp(UnOp::Not, a.clone())), + // Transform "Eq(a, false)" ==> "Not(a)" + (BinOp::Eq, _, Some(false)) => Rvalue::UnaryOp(UnOp::Not, a.clone()), - // Transform "Ne(a, true)" ==> "Not(a)" - (BinOp::Ne, _, Some(true)) => Some(Rvalue::UnaryOp(UnOp::Not, a.clone())), + // Transform "Ne(a, true)" ==> "Not(a)" + (BinOp::Ne, _, Some(true)) => Rvalue::UnaryOp(UnOp::Not, a.clone()), - _ => None, - }; - - if let Some(new) = new { - *rvalue = new; - } - } - - _ => {} - } + _ => return, + }; } fn try_eval_bool(&self, a: &Operand<'_>) -> Option<bool> { @@ -151,64 +141,58 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { /// Transform `&(*a)` ==> `a`. 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), - })); - } + if let Rvalue::Ref(_, _, place) | Rvalue::RawPtr(_, place) = rvalue + && let Some((base, ProjectionElem::Deref)) = place.as_ref().last_projection() + && rvalue.ty(self.local_decls, self.tcx) == base.ty(self.local_decls, self.tcx).ty + { + *rvalue = Rvalue::Use(Operand::Copy(Place { + local: base.local, + projection: self.tcx.mk_place_elems(base.projection), + })); } } /// Transform `Aggregate(RawPtr, [p, ()])` ==> `Cast(PtrToPtr, p)`. 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) + && meta_ty.is_unit() { - let meta_ty = fields.raw[1].ty(self.local_decls, self.tcx); - if meta_ty.is_unit() { - // The mutable borrows we're holding prevent printing `rvalue` here - 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); - } + // The mutable borrows we're holding prevent printing `rvalue` here + 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))); - } + let Rvalue::NullaryOp(NullOp::UbChecks, _) = *rvalue else { return }; + + 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 { - // Transmuting an integer to another integer is just a signedness cast - 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() - { - // The width check isn't strictly necessary, as different widths - // are UB and thus we'd be allowed to turn it into a cast anyway. - // But let's keep the UB around for codegen to exploit later. - // (If `CastKind::Transmute` ever becomes *not* UB for mismatched sizes, - // then the width check is necessary for big-endian correctness.) - *kind = CastKind::IntToInt; - return; - } - } + let Rvalue::Cast(kind, operand, cast_ty) = rvalue else { return }; + + 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 + // Transmuting an integer to another integer is just a signedness cast + && 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() + { + // The width check isn't strictly necessary, as different widths + // are UB and thus we'd be allowed to turn it into a cast anyway. + // But let's keep the UB around for codegen to exploit later. + // (If `CastKind::Transmute` ever becomes *not* UB for mismatched sizes, + // then the width check is necessary for big-endian correctness.) + *kind = CastKind::IntToInt; } } @@ -229,7 +213,9 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { terminator: &mut Terminator<'tcx>, statements: &mut Vec<Statement<'tcx>>, ) { - let TerminatorKind::Call { func, args, destination, target, .. } = &mut terminator.kind + let TerminatorKind::Call { + func, args, destination, target: Some(destination_block), .. + } = &terminator.kind else { return; }; @@ -237,15 +223,8 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { // It's definitely not a clone if there are multiple arguments let [arg] = &args[..] else { return }; - let Some(destination_block) = *target else { return }; - // Only bother looking more if it's easy to know what we're calling - let Some((fn_def_id, fn_args)) = func.const_fn_def() else { return }; - - // Clone needs one arg, so we can cheaply rule out other stuff - if fn_args.len() != 1 { - return; - } + let Some((fn_def_id, ..)) = func.const_fn_def() else { return }; // These types are easily available from locals, so check that before // doing DefId lookups to figure out what we're actually calling. @@ -253,15 +232,12 @@ impl<'tcx> InstSimplifyContext<'_, '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) { + if !self.tcx.is_lang_item(fn_def_id, LangItem::CloneFn) + || !inner_ty.is_trivially_pure_clone_copy() + { return; } - let Ok([arg]) = take_array(args) else { return }; let Some(arg_place) = arg.node.place() else { return }; statements.push(Statement { @@ -273,11 +249,11 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { )), ))), }); - terminator.kind = TerminatorKind::Goto { target: destination_block }; + 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 { + let TerminatorKind::Call { ref func, ref mut unwind, .. } = terminator.kind else { return; }; @@ -290,7 +266,7 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { ty::FnDef(..) => body_ty.fn_sig(self.tcx).abi(), ty::Closure(..) => ExternAbi::RustCall, ty::Coroutine(..) => ExternAbi::Rust, - _ => bug!("unexpected body ty: {:?}", body_ty), + _ => bug!("unexpected body ty: {body_ty:?}"), }; if !layout::fn_can_unwind(self.tcx, Some(def_id), body_abi) { @@ -299,10 +275,9 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { } 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 { + let TerminatorKind::Call { ref func, target: ref mut target @ Some(target_block), .. } = + terminator.kind + else { return; }; let func_ty = func.ty(self.local_decls, self.tcx); @@ -310,12 +285,10 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { return; }; // The intrinsics we are interested in have one generic parameter - if args.is_empty() { - return; - } + let [arg, ..] = args[..] else { return }; let known_is_valid = - intrinsic_assert_panics(self.tcx, self.typing_env, args[0], intrinsic_name); + intrinsic_assert_panics(self.tcx, self.typing_env, arg, intrinsic_name); match known_is_valid { // We don't know the layout or it's not validity assertion at all, don't touch it None => {} @@ -325,7 +298,7 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> { } Some(false) => { // If we know the assert does not panic, turn the call into a Goto - terminator.kind = TerminatorKind::Goto { target: *target_block }; + terminator.kind = TerminatorKind::Goto { target: target_block }; } } } @@ -346,9 +319,7 @@ 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 + let ty::FnDef(def_id, args) = *func_ty.kind() else { return None }; + let intrinsic = tcx.intrinsic(def_id)?; + Some((intrinsic.name, args)) } |