From f20af8d43d9193a2f865ae0361e80158bce0a0a2 Mon Sep 17 00:00:00 2001 From: Scott McMurray Date: Sat, 25 Mar 2023 14:32:31 -0700 Subject: [PATCH] Simplify transmutes in MIR InstCombine Thanks to the combination of #108246 and #108442 it could already remove identity transmutes. With this PR, it can also simplify them to `IntToInt` casts, `Discriminant` reads, or `Field` projections. --- .../rustc_mir_transform/src/instcombine.rs | 54 +++++- ...transmutes.adt_transmutes.InstCombine.diff | 158 ++++++++++++++++++ ...mutes.identity_transmutes.InstCombine.diff | 43 +++++ ...smutes.integer_transmutes.InstCombine.diff | 24 +++ tests/mir-opt/combine_transmutes.rs | 65 +++++++ 5 files changed, 340 insertions(+), 4 deletions(-) create mode 100644 tests/mir-opt/combine_transmutes.adt_transmutes.InstCombine.diff create mode 100644 tests/mir-opt/combine_transmutes.identity_transmutes.InstCombine.diff create mode 100644 tests/mir-opt/combine_transmutes.integer_transmutes.InstCombine.diff create mode 100644 tests/mir-opt/combine_transmutes.rs diff --git a/compiler/rustc_mir_transform/src/instcombine.rs b/compiler/rustc_mir_transform/src/instcombine.rs index c926390aa2b87..c9750e899a51e 100644 --- a/compiler/rustc_mir_transform/src/instcombine.rs +++ b/compiler/rustc_mir_transform/src/instcombine.rs @@ -3,10 +3,12 @@ use crate::MirPass; use rustc_hir::Mutability; use rustc_middle::mir::{ - BinOp, Body, Constant, ConstantKind, LocalDecls, Operand, Place, ProjectionElem, Rvalue, - SourceInfo, Statement, StatementKind, SwitchTargets, Terminator, TerminatorKind, UnOp, + BinOp, Body, CastKind, Constant, ConstantKind, Field, LocalDecls, Operand, Place, + ProjectionElem, Rvalue, SourceInfo, Statement, StatementKind, SwitchTargets, Terminator, + TerminatorKind, UnOp, }; use rustc_middle::ty::layout::ValidityRequirement; +use rustc_middle::ty::util::IntTypeExt; use rustc_middle::ty::{self, ParamEnv, SubstsRef, Ty, TyCtxt}; use rustc_span::symbol::Symbol; @@ -145,9 +147,53 @@ impl<'tcx> InstCombineContext<'tcx, '_> { } fn combine_cast(&self, _source_info: &SourceInfo, rvalue: &mut Rvalue<'tcx>) { - if let Rvalue::Cast(_kind, operand, ty) = rvalue { - if operand.ty(self.local_decls, self.tcx) == *ty { + 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; + } + + // Transmuting a fieldless enum to its repr is a discriminant read + if let ty::Adt(adt_def, ..) = operand_ty.kind() + && adt_def.is_enum() + && adt_def.is_payloadfree() + && let Some(place) = operand.place() + && let Some(repr_int) = adt_def.repr().int + && repr_int.to_ty(self.tcx) == *cast_ty + { + *rvalue = Rvalue::Discriminant(place); + return; + } + + // Transmuting a transparent struct/union to a field's type is a projection + if let ty::Adt(adt_def, substs) = 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().enumerate() { + let field_ty = field.ty(self.tcx, substs); + if field_ty == *cast_ty { + let place = place.project_deeper(&[ProjectionElem::Field(Field::from_usize(i), *cast_ty)], self.tcx); + let operand = if operand.is_move() { Operand::Move(place) } else { Operand::Copy(place) }; + *rvalue = Rvalue::Use(operand); + return; + } + } + } } } } diff --git a/tests/mir-opt/combine_transmutes.adt_transmutes.InstCombine.diff b/tests/mir-opt/combine_transmutes.adt_transmutes.InstCombine.diff new file mode 100644 index 0000000000000..c44a14075ef6f --- /dev/null +++ b/tests/mir-opt/combine_transmutes.adt_transmutes.InstCombine.diff @@ -0,0 +1,158 @@ +- // MIR for `adt_transmutes` before InstCombine ++ // MIR for `adt_transmutes` after InstCombine + + fn adt_transmutes() -> () { + let mut _0: (); // return place in scope 0 at $DIR/combine_transmutes.rs:+0:32: +0:32 + let _1: u8; // in scope 0 at $DIR/combine_transmutes.rs:+1:9: +1:11 + let mut _2: EnumNoRepr; // in scope 0 at $DIR/combine_transmutes.rs:+1:28: +1:41 + let mut _4: EnumNoRepr; // in scope 0 at $DIR/combine_transmutes.rs:+2:28: +2:41 + let mut _6: EnumReprIsize; // in scope 0 at $DIR/combine_transmutes.rs:+3:31: +3:47 + let mut _8: EnumReprIsize; // in scope 0 at $DIR/combine_transmutes.rs:+4:31: +4:47 + let mut _10: std::cmp::Ordering; // in scope 0 at $DIR/combine_transmutes.rs:+5:28: +5:52 + let mut _12: std::cmp::Ordering; // in scope 0 at $DIR/combine_transmutes.rs:+6:28: +6:52 + let mut _14: std::option::Option; // in scope 0 at $DIR/combine_transmutes.rs:+7:28: +7:58 + let mut _16: std::num::Wrapping; // in scope 0 at $DIR/combine_transmutes.rs:+8:29: +8:54 + let mut _18: std::num::Wrapping; // in scope 0 at $DIR/combine_transmutes.rs:+9:29: +9:54 + let mut _20: Union32; // in scope 0 at $DIR/combine_transmutes.rs:+10:29: +10:47 + let mut _22: Union32; // in scope 0 at $DIR/combine_transmutes.rs:+11:29: +11:47 + let mut _24: std::mem::MaybeUninit; // in scope 0 at $DIR/combine_transmutes.rs:+12:46: +12:77 + scope 1 { + debug _a => _1; // in scope 1 at $DIR/combine_transmutes.rs:+1:9: +1:11 + let _3: i8; // in scope 1 at $DIR/combine_transmutes.rs:+2:9: +2:11 + scope 2 { + debug _a => _3; // in scope 2 at $DIR/combine_transmutes.rs:+2:9: +2:11 + let _5: usize; // in scope 2 at $DIR/combine_transmutes.rs:+3:9: +3:11 + scope 3 { + debug _a => _5; // in scope 3 at $DIR/combine_transmutes.rs:+3:9: +3:11 + let _7: isize; // in scope 3 at $DIR/combine_transmutes.rs:+4:9: +4:11 + scope 4 { + debug _a => _7; // in scope 4 at $DIR/combine_transmutes.rs:+4:9: +4:11 + let _9: u8; // in scope 4 at $DIR/combine_transmutes.rs:+5:9: +5:11 + scope 5 { + debug _a => _9; // in scope 5 at $DIR/combine_transmutes.rs:+5:9: +5:11 + let _11: i8; // in scope 5 at $DIR/combine_transmutes.rs:+6:9: +6:11 + scope 6 { + debug _a => _11; // in scope 6 at $DIR/combine_transmutes.rs:+6:9: +6:11 + let _13: u8; // in scope 6 at $DIR/combine_transmutes.rs:+7:9: +7:11 + scope 7 { + debug _a => _13; // in scope 7 at $DIR/combine_transmutes.rs:+7:9: +7:11 + let _15: i16; // in scope 7 at $DIR/combine_transmutes.rs:+8:9: +8:11 + scope 8 { + debug _a => _15; // in scope 8 at $DIR/combine_transmutes.rs:+8:9: +8:11 + let _17: u16; // in scope 8 at $DIR/combine_transmutes.rs:+9:9: +9:11 + scope 9 { + debug _a => _17; // in scope 9 at $DIR/combine_transmutes.rs:+9:9: +9:11 + let _19: u32; // in scope 9 at $DIR/combine_transmutes.rs:+10:9: +10:11 + scope 10 { + debug _a => _19; // in scope 10 at $DIR/combine_transmutes.rs:+10:9: +10:11 + let _21: i32; // in scope 10 at $DIR/combine_transmutes.rs:+11:9: +11:11 + scope 11 { + debug _a => _21; // in scope 11 at $DIR/combine_transmutes.rs:+11:9: +11:11 + let _23: std::mem::ManuallyDrop; // in scope 11 at $DIR/combine_transmutes.rs:+12:9: +12:11 + scope 12 { + debug _a => _23; // in scope 12 at $DIR/combine_transmutes.rs:+12:9: +12:11 + } + } + } + } + } + } + } + } + } + } + } + } + + bb0: { + StorageLive(_1); // scope 0 at $DIR/combine_transmutes.rs:+1:9: +1:11 + StorageLive(_2); // scope 0 at $DIR/combine_transmutes.rs:+1:28: +1:41 + _2 = EnumNoRepr::A; // scope 0 at $DIR/combine_transmutes.rs:+1:28: +1:41 + _1 = move _2 as u8 (Transmute); // scope 0 at $DIR/combine_transmutes.rs:+1:18: +1:42 + StorageDead(_2); // scope 0 at $DIR/combine_transmutes.rs:+1:41: +1:42 + StorageLive(_3); // scope 1 at $DIR/combine_transmutes.rs:+2:9: +2:11 + StorageLive(_4); // scope 1 at $DIR/combine_transmutes.rs:+2:28: +2:41 + _4 = EnumNoRepr::B; // scope 1 at $DIR/combine_transmutes.rs:+2:28: +2:41 + _3 = move _4 as i8 (Transmute); // scope 1 at $DIR/combine_transmutes.rs:+2:18: +2:42 + StorageDead(_4); // scope 1 at $DIR/combine_transmutes.rs:+2:41: +2:42 + StorageLive(_5); // scope 2 at $DIR/combine_transmutes.rs:+3:9: +3:11 + StorageLive(_6); // scope 2 at $DIR/combine_transmutes.rs:+3:31: +3:47 + _6 = EnumReprIsize::A; // scope 2 at $DIR/combine_transmutes.rs:+3:31: +3:47 + _5 = move _6 as usize (Transmute); // scope 2 at $DIR/combine_transmutes.rs:+3:21: +3:48 + StorageDead(_6); // scope 2 at $DIR/combine_transmutes.rs:+3:47: +3:48 + StorageLive(_7); // scope 3 at $DIR/combine_transmutes.rs:+4:9: +4:11 + StorageLive(_8); // scope 3 at $DIR/combine_transmutes.rs:+4:31: +4:47 + _8 = EnumReprIsize::B; // scope 3 at $DIR/combine_transmutes.rs:+4:31: +4:47 +- _7 = move _8 as isize (Transmute); // scope 3 at $DIR/combine_transmutes.rs:+4:21: +4:48 ++ _7 = discriminant(_8); // scope 3 at $DIR/combine_transmutes.rs:+4:21: +4:48 + StorageDead(_8); // scope 3 at $DIR/combine_transmutes.rs:+4:47: +4:48 + StorageLive(_9); // scope 4 at $DIR/combine_transmutes.rs:+5:9: +5:11 + StorageLive(_10); // scope 4 at $DIR/combine_transmutes.rs:+5:28: +5:52 + _10 = Less; // scope 4 at $DIR/combine_transmutes.rs:+5:28: +5:52 + _9 = move _10 as u8 (Transmute); // scope 4 at $DIR/combine_transmutes.rs:+5:18: +5:53 + StorageDead(_10); // scope 4 at $DIR/combine_transmutes.rs:+5:52: +5:53 + StorageLive(_11); // scope 5 at $DIR/combine_transmutes.rs:+6:9: +6:11 + StorageLive(_12); // scope 5 at $DIR/combine_transmutes.rs:+6:28: +6:52 + _12 = Less; // scope 5 at $DIR/combine_transmutes.rs:+6:28: +6:52 +- _11 = move _12 as i8 (Transmute); // scope 5 at $DIR/combine_transmutes.rs:+6:18: +6:53 ++ _11 = discriminant(_12); // scope 5 at $DIR/combine_transmutes.rs:+6:18: +6:53 + StorageDead(_12); // scope 5 at $DIR/combine_transmutes.rs:+6:52: +6:53 + StorageLive(_13); // scope 6 at $DIR/combine_transmutes.rs:+7:9: +7:11 + StorageLive(_14); // scope 6 at $DIR/combine_transmutes.rs:+7:28: +7:58 + _14 = Option::::Some(const _); // scope 6 at $DIR/combine_transmutes.rs:+7:28: +7:58 + // mir::Constant + // + span: $DIR/combine_transmutes.rs:41:33: 41:57 + // + literal: Const { ty: NonZeroU8, val: Unevaluated(NonZeroU8::MAX, [], None) } + _13 = move _14 as u8 (Transmute); // scope 6 at $DIR/combine_transmutes.rs:+7:18: +7:59 + StorageDead(_14); // scope 6 at $DIR/combine_transmutes.rs:+7:58: +7:59 + StorageLive(_15); // scope 7 at $DIR/combine_transmutes.rs:+8:9: +8:11 + StorageLive(_16); // scope 7 at $DIR/combine_transmutes.rs:+8:29: +8:54 + _16 = Wrapping::(const 0_i16); // scope 7 at $DIR/combine_transmutes.rs:+8:29: +8:54 +- _15 = move _16 as i16 (Transmute); // scope 7 at $DIR/combine_transmutes.rs:+8:19: +8:55 ++ _15 = move (_16.0: i16); // scope 7 at $DIR/combine_transmutes.rs:+8:19: +8:55 + StorageDead(_16); // scope 7 at $DIR/combine_transmutes.rs:+8:54: +8:55 + StorageLive(_17); // scope 8 at $DIR/combine_transmutes.rs:+9:9: +9:11 + StorageLive(_18); // scope 8 at $DIR/combine_transmutes.rs:+9:29: +9:54 + _18 = Wrapping::(const 0_i16); // scope 8 at $DIR/combine_transmutes.rs:+9:29: +9:54 + _17 = move _18 as u16 (Transmute); // scope 8 at $DIR/combine_transmutes.rs:+9:19: +9:55 + StorageDead(_18); // scope 8 at $DIR/combine_transmutes.rs:+9:54: +9:55 + StorageLive(_19); // scope 9 at $DIR/combine_transmutes.rs:+10:9: +10:11 + StorageLive(_20); // scope 9 at $DIR/combine_transmutes.rs:+10:29: +10:47 + _20 = Union32 { u32: const 0_i32 }; // scope 9 at $DIR/combine_transmutes.rs:+10:29: +10:47 + _19 = move _20 as u32 (Transmute); // scope 9 at $DIR/combine_transmutes.rs:+10:19: +10:48 + StorageDead(_20); // scope 9 at $DIR/combine_transmutes.rs:+10:47: +10:48 + StorageLive(_21); // scope 10 at $DIR/combine_transmutes.rs:+11:9: +11:11 + StorageLive(_22); // scope 10 at $DIR/combine_transmutes.rs:+11:29: +11:47 + _22 = Union32 { u32: const 0_u32 }; // scope 10 at $DIR/combine_transmutes.rs:+11:29: +11:47 + _21 = move _22 as i32 (Transmute); // scope 10 at $DIR/combine_transmutes.rs:+11:19: +11:48 + StorageDead(_22); // scope 10 at $DIR/combine_transmutes.rs:+11:47: +11:48 + StorageLive(_23); // scope 11 at $DIR/combine_transmutes.rs:+12:9: +12:11 + StorageLive(_24); // scope 11 at $DIR/combine_transmutes.rs:+12:46: +12:77 + _24 = MaybeUninit::::uninit() -> bb1; // scope 11 at $DIR/combine_transmutes.rs:+12:46: +12:77 + // mir::Constant + // + span: $DIR/combine_transmutes.rs:46:46: 46:75 + // + user_ty: UserType(23) + // + literal: Const { ty: fn() -> MaybeUninit {MaybeUninit::::uninit}, val: Value() } + } + + bb1: { +- _23 = move _24 as std::mem::ManuallyDrop (Transmute); // scope 11 at $DIR/combine_transmutes.rs:+12:36: +12:78 ++ _23 = move (_24.1: std::mem::ManuallyDrop); // scope 11 at $DIR/combine_transmutes.rs:+12:36: +12:78 + StorageDead(_24); // scope 11 at $DIR/combine_transmutes.rs:+12:77: +12:78 + _0 = const (); // scope 0 at $DIR/combine_transmutes.rs:+0:32: +13:2 + StorageDead(_23); // scope 11 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_21); // scope 10 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_19); // scope 9 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_17); // scope 8 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_15); // scope 7 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_13); // scope 6 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_11); // scope 5 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_9); // scope 4 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_7); // scope 3 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_5); // scope 2 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_3); // scope 1 at $DIR/combine_transmutes.rs:+13:1: +13:2 + StorageDead(_1); // scope 0 at $DIR/combine_transmutes.rs:+13:1: +13:2 + return; // scope 0 at $DIR/combine_transmutes.rs:+13:2: +13:2 + } + } + diff --git a/tests/mir-opt/combine_transmutes.identity_transmutes.InstCombine.diff b/tests/mir-opt/combine_transmutes.identity_transmutes.InstCombine.diff new file mode 100644 index 0000000000000..c83c9f5acf484 --- /dev/null +++ b/tests/mir-opt/combine_transmutes.identity_transmutes.InstCombine.diff @@ -0,0 +1,43 @@ +- // MIR for `identity_transmutes` before InstCombine ++ // MIR for `identity_transmutes` after InstCombine + + fn identity_transmutes() -> () { + let mut _0: (); // return place in scope 0 at $DIR/combine_transmutes.rs:+0:37: +0:37 + let _1: i32; // in scope 0 at $DIR/combine_transmutes.rs:+2:9: +2:11 + let mut _3: std::vec::Vec; // in scope 0 at $DIR/combine_transmutes.rs:+3:46: +3:56 + scope 1 { + debug _a => _1; // in scope 1 at $DIR/combine_transmutes.rs:+2:9: +2:11 + let _2: std::vec::Vec; // in scope 1 at $DIR/combine_transmutes.rs:+3:9: +3:11 + scope 2 { + debug _a => _2; // in scope 2 at $DIR/combine_transmutes.rs:+3:9: +3:11 + } + } + + bb0: { + StorageLive(_1); // scope 0 at $DIR/combine_transmutes.rs:+2:9: +2:11 +- _1 = const 1_i32 as i32 (Transmute); // scope 0 at $DIR/combine_transmutes.rs:+2:14: +2:38 ++ _1 = const 1_i32; // scope 0 at $DIR/combine_transmutes.rs:+2:14: +2:38 + StorageLive(_2); // scope 1 at $DIR/combine_transmutes.rs:+3:9: +3:11 + StorageLive(_3); // scope 1 at $DIR/combine_transmutes.rs:+3:46: +3:56 + _3 = Vec::::new() -> bb1; // scope 1 at $DIR/combine_transmutes.rs:+3:46: +3:56 + // mir::Constant + // + span: $DIR/combine_transmutes.rs:15:46: 15:54 + // + user_ty: UserType(0) + // + literal: Const { ty: fn() -> Vec {Vec::::new}, val: Value() } + } + + bb1: { +- _2 = move _3 as std::vec::Vec (Transmute); // scope 1 at $DIR/combine_transmutes.rs:+3:14: +3:57 ++ _2 = move _3; // scope 1 at $DIR/combine_transmutes.rs:+3:14: +3:57 + StorageDead(_3); // scope 1 at $DIR/combine_transmutes.rs:+3:56: +3:57 + _0 = const (); // scope 0 at $DIR/combine_transmutes.rs:+0:37: +4:2 + drop(_2) -> bb2; // scope 1 at $DIR/combine_transmutes.rs:+4:1: +4:2 + } + + bb2: { + StorageDead(_2); // scope 1 at $DIR/combine_transmutes.rs:+4:1: +4:2 + StorageDead(_1); // scope 0 at $DIR/combine_transmutes.rs:+4:1: +4:2 + return; // scope 0 at $DIR/combine_transmutes.rs:+4:2: +4:2 + } + } + diff --git a/tests/mir-opt/combine_transmutes.integer_transmutes.InstCombine.diff b/tests/mir-opt/combine_transmutes.integer_transmutes.InstCombine.diff new file mode 100644 index 0000000000000..8de7c34e6b2da --- /dev/null +++ b/tests/mir-opt/combine_transmutes.integer_transmutes.InstCombine.diff @@ -0,0 +1,24 @@ +- // MIR for `integer_transmutes` before InstCombine ++ // MIR for `integer_transmutes` after InstCombine + + fn integer_transmutes() -> () { + let mut _0: (); // return place in scope 0 at $DIR/combine_transmutes.rs:+0:36: +0:36 + let mut _1: u32; // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL + let mut _2: i64; // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL + let mut _3: i64; // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL + let mut _4: u32; // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL + let mut _5: usize; // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL + + bb0: { +- _1 = const 1_i32 as u32 (Transmute); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL ++ _1 = const 1_i32 as u32 (IntToInt); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL + _2 = const 1_i32 as i64 (Transmute); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL +- _3 = const 1_u64 as i64 (Transmute); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL ++ _3 = const 1_u64 as i64 (IntToInt); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL + _4 = const 1_u64 as u32 (Transmute); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL +- _5 = const 1_isize as usize (Transmute); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL ++ _5 = const 1_isize as usize (IntToInt); // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL + return; // scope 0 at $DIR/combine_transmutes.rs:+8:13: +8:21 + } + } + diff --git a/tests/mir-opt/combine_transmutes.rs b/tests/mir-opt/combine_transmutes.rs new file mode 100644 index 0000000000000..de9b9c35c030b --- /dev/null +++ b/tests/mir-opt/combine_transmutes.rs @@ -0,0 +1,65 @@ +// unit-test: InstCombine +// compile-flags: -C panic=abort + +#![crate_type = "lib"] +#![feature(core_intrinsics)] +#![feature(custom_mir)] + +use std::intrinsics::mir::*; +use std::mem::{MaybeUninit, ManuallyDrop, transmute}; + +// EMIT_MIR combine_transmutes.identity_transmutes.InstCombine.diff +pub unsafe fn identity_transmutes() { + // These are nops and should be removed + let _a = transmute::(1); + let _a = transmute::, Vec>(Vec::new()); +} + +#[custom_mir(dialect = "runtime", phase = "initial")] +// EMIT_MIR combine_transmutes.integer_transmutes.InstCombine.diff +pub unsafe fn integer_transmutes() { + mir! { + { + let A = CastTransmute::(1); // Can be a cast + let B = CastTransmute::(1); // UB + let C = CastTransmute::(1); // Can be a cast + let D = CastTransmute::(1); // UB + let E = CastTransmute::(1); // Can be a cast + Return() + } + } +} + +// EMIT_MIR combine_transmutes.adt_transmutes.InstCombine.diff +pub unsafe fn adt_transmutes() { + let _a: u8 = transmute(EnumNoRepr::A); + let _a: i8 = transmute(EnumNoRepr::B); + let _a: usize = transmute(EnumReprIsize::A); + let _a: isize = transmute(EnumReprIsize::B); + let _a: u8 = transmute(std::cmp::Ordering::Less); + let _a: i8 = transmute(std::cmp::Ordering::Less); + let _a: u8 = transmute(Some(std::num::NonZeroU8::MAX)); + let _a: i16 = transmute(std::num::Wrapping(0_i16)); + let _a: u16 = transmute(std::num::Wrapping(0_i16)); + let _a: u32 = transmute(Union32 { i32: 0 }); + let _a: i32 = transmute(Union32 { u32: 0 }); + let _a: ManuallyDrop = transmute(MaybeUninit::::uninit()); +} + +#[inline(always)] +#[custom_mir(dialect = "runtime", phase = "initial")] +const unsafe fn mir_transmute(x: T) -> U { + mir!{ + { + RET = CastTransmute(x); + Return() + } + } +} + +pub enum EnumNoRepr { A, B, C } + +#[repr(isize)] +pub enum EnumReprIsize { A, B, C } + +pub union Union32 { u32: u32, i32: i32 }