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Lower unchecked_div/_rem to MIR's BinOp::Div/Rem #112168

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merged 5 commits into from
Jun 3, 2023
Merged

Lower unchecked_div/_rem to MIR's BinOp::Div/Rem #112168

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32cc106
Lower unchecked_{div, rem} to BinOp::{Div, Rem}
scottmcm Jun 1, 2023
bfb9233
remove unchecked_div/_rem from cg_cranelift
scottmcm Jun 1, 2023
dc353f1
remove unchecked_div/_rem from cg_ssa
scottmcm Jun 1, 2023
73f104b
remove unchecked_div/_rem from ctfe
scottmcm Jun 1, 2023
adb37d4
Clarify when MIR `Div`/`Rem` trigger UB
scottmcm Jun 2, 2023
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5 changes: 1 addition & 4 deletions compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
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Expand Up @@ -475,9 +475,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
sym::unchecked_add
| sym::unchecked_sub
| sym::unchecked_mul
| sym::unchecked_div
| sym::exact_div
| sym::unchecked_rem
| sym::unchecked_shl
| sym::unchecked_shr => {
intrinsic_args!(fx, args => (x, y); intrinsic);
Expand All @@ -487,8 +485,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
sym::unchecked_add => BinOp::Add,
sym::unchecked_sub => BinOp::Sub,
sym::unchecked_mul => BinOp::Mul,
sym::unchecked_div | sym::exact_div => BinOp::Div,
sym::unchecked_rem => BinOp::Rem,
sym::exact_div => BinOp::Div,
sym::unchecked_shl => BinOp::Shl,
sym::unchecked_shr => BinOp::Shr,
_ => unreachable!(),
Expand Down
16 changes: 0 additions & 16 deletions compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -211,8 +211,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
args[1].val.unaligned_volatile_store(bx, dst);
return;
}
| sym::unchecked_div
| sym::unchecked_rem
| sym::unchecked_shl
| sym::unchecked_shr
| sym::unchecked_add
Expand All @@ -229,20 +227,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
bx.exactudiv(args[0].immediate(), args[1].immediate())
}
}
sym::unchecked_div => {
if signed {
bx.sdiv(args[0].immediate(), args[1].immediate())
} else {
bx.udiv(args[0].immediate(), args[1].immediate())
}
}
sym::unchecked_rem => {
if signed {
bx.srem(args[0].immediate(), args[1].immediate())
} else {
bx.urem(args[0].immediate(), args[1].immediate())
}
}
sym::unchecked_shl => bx.shl(args[0].immediate(), args[1].immediate()),
sym::unchecked_shr => {
if signed {
Expand Down
6 changes: 1 addition & 5 deletions compiler/rustc_const_eval/src/interpret/intrinsics.rs
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Expand Up @@ -233,9 +233,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
| sym::unchecked_shr
| sym::unchecked_add
| sym::unchecked_sub
| sym::unchecked_mul
| sym::unchecked_div
| sym::unchecked_rem => {
| sym::unchecked_mul => {
let l = self.read_immediate(&args[0])?;
let r = self.read_immediate(&args[1])?;
let bin_op = match intrinsic_name {
Expand All @@ -244,8 +242,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
sym::unchecked_add => BinOp::Add,
sym::unchecked_sub => BinOp::Sub,
sym::unchecked_mul => BinOp::Mul,
sym::unchecked_div => BinOp::Div,
sym::unchecked_rem => BinOp::Rem,
_ => bug!(),
};
let (val, overflowed, _ty) = self.overflowing_binary_op(bin_op, &l, &r)?;
Expand Down
13 changes: 9 additions & 4 deletions compiler/rustc_middle/src/mir/syntax.rs
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Expand Up @@ -1272,13 +1272,18 @@ pub enum BinOp {
Mul,
/// The `/` operator (division)
///
/// Division by zero is UB, because the compiler should have inserted checks
/// prior to this.
/// For integer types, division by zero is UB, as is `MIN / -1` for signed.
/// The compiler should have inserted checks prior to this.
///
/// Floating-point division by zero is safe, and does not need guards.
Div,
/// The `%` operator (modulus)
///
/// Using zero as the modulus (second operand) is UB, because the compiler
/// should have inserted checks prior to this.
/// For integer types, using zero as the modulus (second operand) is UB,
/// as is `MIN % -1` for signed.
/// The compiler should have inserted checks prior to this.
///
/// Floating-point remainder by zero is safe, and does not need guards.
Rem,
/// The `^` operator (bitwise xor)
BitXor,
Expand Down
51 changes: 28 additions & 23 deletions compiler/rustc_mir_transform/src/lower_intrinsics.rs
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Expand Up @@ -82,30 +82,35 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
drop(args);
terminator.kind = TerminatorKind::Goto { target };
}
sym::wrapping_add | sym::wrapping_sub | sym::wrapping_mul => {
if let Some(target) = *target {
let lhs;
let rhs;
{
let mut args = args.drain(..);
lhs = args.next().unwrap();
rhs = args.next().unwrap();
}
let bin_op = match intrinsic_name {
sym::wrapping_add => BinOp::Add,
sym::wrapping_sub => BinOp::Sub,
sym::wrapping_mul => BinOp::Mul,
_ => bug!("unexpected intrinsic"),
};
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::BinaryOp(bin_op, Box::new((lhs, rhs))),
))),
});
terminator.kind = TerminatorKind::Goto { target };
sym::wrapping_add
| sym::wrapping_sub
| sym::wrapping_mul
| sym::unchecked_div
| sym::unchecked_rem => {
let target = target.unwrap();
let lhs;
let rhs;
{
let mut args = args.drain(..);
lhs = args.next().unwrap();
rhs = args.next().unwrap();
}
let bin_op = match intrinsic_name {
sym::wrapping_add => BinOp::Add,
sym::wrapping_sub => BinOp::Sub,
sym::wrapping_mul => BinOp::Mul,
sym::unchecked_div => BinOp::Div,
sym::unchecked_rem => BinOp::Rem,
_ => bug!("unexpected intrinsic"),
};
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::BinaryOp(bin_op, Box::new((lhs, rhs))),
))),
});
terminator.kind = TerminatorKind::Goto { target };
}
sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
if let Some(target) = *target {
Expand Down
2 changes: 1 addition & 1 deletion tests/mir-opt/lower_intrinsics.align_of.LowerIntrinsics.diff
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Expand Up @@ -7,7 +7,7 @@
bb0: {
- _0 = std::intrinsics::min_align_of::<T>() -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:42
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:21:5: 21:40
- // + span: $DIR/lower_intrinsics.rs:27:5: 27:40
- // + literal: Const { ty: extern "rust-intrinsic" fn() -> usize {std::intrinsics::min_align_of::<T>}, val: Value(<ZST>) }
+ _0 = AlignOf(T); // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:42
+ goto -> bb1; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:42
Expand Down
2 changes: 1 addition & 1 deletion tests/mir-opt/lower_intrinsics.assume.LowerIntrinsics.diff
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Expand Up @@ -11,7 +11,7 @@
StorageLive(_1); // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:38
- _1 = std::intrinsics::assume(const true) -> [return: bb1, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:38
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:106:9: 106:32
- // + span: $DIR/lower_intrinsics.rs:112:9: 112:32
- // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(bool) {std::intrinsics::assume}, val: Value(<ZST>) }
+ assume(const true); // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:38
+ goto -> bb1; // scope 1 at $DIR/lower_intrinsics.rs:+2:9: +2:38
Expand Down
14 changes: 7 additions & 7 deletions tests/mir-opt/lower_intrinsics.discriminant.LowerIntrinsics.diff
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Expand Up @@ -31,7 +31,7 @@
_3 = &(*_4); // scope 0 at $DIR/lower_intrinsics.rs:+1:42: +1:44
- _2 = discriminant_value::<T>(move _3) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:45
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:82:5: 82:41
- // + span: $DIR/lower_intrinsics.rs:88:5: 88:41
- // + literal: Const { ty: for<'a> extern "rust-intrinsic" fn(&'a T) -> <T as DiscriminantKind>::Discriminant {discriminant_value::<T>}, val: Value(<ZST>) }
+ _2 = discriminant((*_3)); // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:45
+ goto -> bb1; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:45
Expand All @@ -46,13 +46,13 @@
StorageLive(_7); // scope 0 at $DIR/lower_intrinsics.rs:+2:42: +2:44
_19 = const _; // scope 0 at $DIR/lower_intrinsics.rs:+2:42: +2:44
// mir::Constant
// + span: $DIR/lower_intrinsics.rs:83:42: 83:44
// + span: $DIR/lower_intrinsics.rs:89:42: 89:44
// + literal: Const { ty: &i32, val: Unevaluated(discriminant, [T], Some(promoted[2])) }
_7 = &(*_19); // scope 0 at $DIR/lower_intrinsics.rs:+2:42: +2:44
_6 = &(*_7); // scope 0 at $DIR/lower_intrinsics.rs:+2:42: +2:44
- _5 = discriminant_value::<i32>(move _6) -> [return: bb2, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+2:5: +2:45
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:83:5: 83:41
- // + span: $DIR/lower_intrinsics.rs:89:5: 89:41
- // + literal: Const { ty: for<'a> extern "rust-intrinsic" fn(&'a i32) -> <i32 as DiscriminantKind>::Discriminant {discriminant_value::<i32>}, val: Value(<ZST>) }
+ _5 = discriminant((*_6)); // scope 0 at $DIR/lower_intrinsics.rs:+2:5: +2:45
+ goto -> bb2; // scope 0 at $DIR/lower_intrinsics.rs:+2:5: +2:45
Expand All @@ -67,13 +67,13 @@
StorageLive(_11); // scope 0 at $DIR/lower_intrinsics.rs:+3:42: +3:45
_18 = const _; // scope 0 at $DIR/lower_intrinsics.rs:+3:42: +3:45
// mir::Constant
// + span: $DIR/lower_intrinsics.rs:84:42: 84:45
// + span: $DIR/lower_intrinsics.rs:90:42: 90:45
// + literal: Const { ty: &(), val: Unevaluated(discriminant, [T], Some(promoted[1])) }
_11 = &(*_18); // scope 0 at $DIR/lower_intrinsics.rs:+3:42: +3:45
_10 = &(*_11); // scope 0 at $DIR/lower_intrinsics.rs:+3:42: +3:45
- _9 = discriminant_value::<()>(move _10) -> [return: bb3, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+3:5: +3:46
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:84:5: 84:41
- // + span: $DIR/lower_intrinsics.rs:90:5: 90:41
- // + literal: Const { ty: for<'a> extern "rust-intrinsic" fn(&'a ()) -> <() as DiscriminantKind>::Discriminant {discriminant_value::<()>}, val: Value(<ZST>) }
+ _9 = discriminant((*_10)); // scope 0 at $DIR/lower_intrinsics.rs:+3:5: +3:46
+ goto -> bb3; // scope 0 at $DIR/lower_intrinsics.rs:+3:5: +3:46
Expand All @@ -88,13 +88,13 @@
StorageLive(_15); // scope 0 at $DIR/lower_intrinsics.rs:+4:42: +4:47
_17 = const _; // scope 0 at $DIR/lower_intrinsics.rs:+4:42: +4:47
// mir::Constant
// + span: $DIR/lower_intrinsics.rs:85:42: 85:47
// + span: $DIR/lower_intrinsics.rs:91:42: 91:47
// + literal: Const { ty: &E, val: Unevaluated(discriminant, [T], Some(promoted[0])) }
_15 = &(*_17); // scope 0 at $DIR/lower_intrinsics.rs:+4:42: +4:47
_14 = &(*_15); // scope 0 at $DIR/lower_intrinsics.rs:+4:42: +4:47
- _13 = discriminant_value::<E>(move _14) -> [return: bb4, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+4:5: +4:48
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:85:5: 85:41
- // + span: $DIR/lower_intrinsics.rs:91:5: 91:41
- // + literal: Const { ty: for<'a> extern "rust-intrinsic" fn(&'a E) -> <E as DiscriminantKind>::Discriminant {discriminant_value::<E>}, val: Value(<ZST>) }
+ _13 = discriminant((*_14)); // scope 0 at $DIR/lower_intrinsics.rs:+4:5: +4:48
+ goto -> bb4; // scope 0 at $DIR/lower_intrinsics.rs:+4:5: +4:48
Expand Down
2 changes: 1 addition & 1 deletion tests/mir-opt/lower_intrinsics.f_copy_nonoverlapping.LowerIntrinsics.diff
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Expand Up @@ -49,7 +49,7 @@
StorageDead(_9); // scope 3 at $DIR/lower_intrinsics.rs:+4:90: +4:91
- _3 = copy_nonoverlapping::<i32>(move _4, move _8, const 0_usize) -> [return: bb1, unwind unreachable]; // scope 3 at $DIR/lower_intrinsics.rs:+4:9: +4:95
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:99:9: 99:28
- // + span: $DIR/lower_intrinsics.rs:105:9: 105:28
- // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const i32, *mut i32, usize) {copy_nonoverlapping::<i32>}, val: Value(<ZST>) }
+ copy_nonoverlapping(dst = move _8, src = move _4, count = const 0_usize); // scope 3 at $DIR/lower_intrinsics.rs:+4:9: +4:95
+ goto -> bb1; // scope 3 at $DIR/lower_intrinsics.rs:+4:9: +4:95
Expand Down
2 changes: 1 addition & 1 deletion tests/mir-opt/lower_intrinsics.forget.LowerIntrinsics.diff
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Expand Up @@ -11,7 +11,7 @@
_2 = move _1; // scope 0 at $DIR/lower_intrinsics.rs:+1:30: +1:31
- _0 = std::intrinsics::forget::<T>(move _2) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:32
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:26:5: 26:29
- // + span: $DIR/lower_intrinsics.rs:32:5: 32:29
- // + literal: Const { ty: extern "rust-intrinsic" fn(T) {std::intrinsics::forget::<T>}, val: Value(<ZST>) }
+ _0 = const (); // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:32
+ goto -> bb1; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:32
Expand Down
2 changes: 1 addition & 1 deletion tests/mir-opt/lower_intrinsics.non_const.LowerIntrinsics.diff
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Expand Up @@ -13,7 +13,7 @@
StorageLive(_1); // scope 0 at $DIR/lower_intrinsics.rs:+2:9: +2:18
_1 = std::intrinsics::size_of::<T>; // scope 0 at $DIR/lower_intrinsics.rs:+2:21: +2:51
// mir::Constant
// + span: $DIR/lower_intrinsics.rs:37:21: 37:51
// + span: $DIR/lower_intrinsics.rs:43:21: 43:51
// + literal: Const { ty: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>}, val: Value(<ZST>) }
StorageLive(_2); // scope 1 at $DIR/lower_intrinsics.rs:+3:5: +3:14
_2 = _1; // scope 1 at $DIR/lower_intrinsics.rs:+3:5: +3:14
Expand Down
4 changes: 2 additions & 2 deletions tests/mir-opt/lower_intrinsics.option_payload.LowerIntrinsics.diff
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Expand Up @@ -24,7 +24,7 @@
_4 = &raw const (*_1); // scope 1 at $DIR/lower_intrinsics.rs:+2:55: +2:56
- _3 = option_payload_ptr::<usize>(move _4) -> [return: bb1, unwind unreachable]; // scope 1 at $DIR/lower_intrinsics.rs:+2:18: +2:57
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:137:18: 137:54
- // + span: $DIR/lower_intrinsics.rs:143:18: 143:54
- // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const Option<usize>) -> *const usize {option_payload_ptr::<usize>}, val: Value(<ZST>) }
+ _3 = &raw const (((*_4) as Some).0: usize); // scope 1 at $DIR/lower_intrinsics.rs:+2:18: +2:57
+ goto -> bb1; // scope 1 at $DIR/lower_intrinsics.rs:+2:18: +2:57
Expand All @@ -37,7 +37,7 @@
_6 = &raw const (*_2); // scope 2 at $DIR/lower_intrinsics.rs:+3:55: +3:56
- _5 = option_payload_ptr::<String>(move _6) -> [return: bb2, unwind unreachable]; // scope 2 at $DIR/lower_intrinsics.rs:+3:18: +3:57
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:138:18: 138:54
- // + span: $DIR/lower_intrinsics.rs:144:18: 144:54
- // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const Option<String>) -> *const String {option_payload_ptr::<String>}, val: Value(<ZST>) }
+ _5 = &raw const (((*_6) as Some).0: std::string::String); // scope 2 at $DIR/lower_intrinsics.rs:+3:18: +3:57
+ goto -> bb2; // scope 2 at $DIR/lower_intrinsics.rs:+3:18: +3:57
Expand Down
2 changes: 1 addition & 1 deletion tests/mir-opt/lower_intrinsics.ptr_offset.LowerIntrinsics.diff
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Expand Up @@ -15,7 +15,7 @@
_4 = _2; // scope 0 at $DIR/lower_intrinsics.rs:+1:33: +1:34
- _0 = offset::<*const i32, isize>(move _3, move _4) -> [return: bb1, unwind unreachable]; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:35
- // mir::Constant
- // + span: $DIR/lower_intrinsics.rs:144:5: 144:29
- // + span: $DIR/lower_intrinsics.rs:150:5: 150:29
- // + literal: Const { ty: unsafe extern "rust-intrinsic" fn(*const i32, isize) -> *const i32 {offset::<*const i32, isize>}, val: Value(<ZST>) }
+ _0 = Offset(move _3, move _4); // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:35
+ goto -> bb1; // scope 0 at $DIR/lower_intrinsics.rs:+1:5: +1:35
Expand Down
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