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Auto merge of #59148 - lcnr:unchecked_maths, r=eddyb
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add support for unchecked math

add compiler support for
```rust
/// Returns the result of an unchecked addition, resulting in
/// undefined behavior when `x + y > T::max_value()` or `x + y < T::min_value()`.
pub fn unchecked_add<T>(x: T, y: T) -> T;

/// Returns the result of an unchecked substraction, resulting in
/// undefined behavior when `x - y > T::max_value()` or `x - y < T::min_value()`.
pub fn unchecked_sub<T>(x: T, y: T) -> T;

/// Returns the result of an unchecked multiplication, resulting in
/// undefined behavior when `x * y > T::max_value()` or `x * y < T::min_value()`.
pub fn unchecked_mul<T>(x: T, y: T) -> T;
```

cc rust-lang/rfcs#2508
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bors committed Jun 3, 2019
2 parents 6ffb8f5 + d7e0834 commit e22b7a3
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Showing 11 changed files with 198 additions and 2 deletions.
15 changes: 15 additions & 0 deletions src/libcore/intrinsics.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1240,6 +1240,21 @@ extern "rust-intrinsic" {
/// y < 0 or y >= N, where N is the width of T in bits.
pub fn unchecked_shr<T>(x: T, y: T) -> T;

/// Returns the result of an unchecked addition, resulting in
/// undefined behavior when `x + y > T::max_value()` or `x + y < T::min_value()`.
#[cfg(not(stage0))]
pub fn unchecked_add<T>(x: T, y: T) -> T;

/// Returns the result of an unchecked substraction, resulting in
/// undefined behavior when `x - y > T::max_value()` or `x - y < T::min_value()`.
#[cfg(not(stage0))]
pub fn unchecked_sub<T>(x: T, y: T) -> T;

/// Returns the result of an unchecked multiplication, resulting in
/// undefined behavior when `x * y > T::max_value()` or `x * y < T::min_value()`.
#[cfg(not(stage0))]
pub fn unchecked_mul<T>(x: T, y: T) -> T;

/// Performs rotate left.
/// The stabilized versions of this intrinsic are available on the integer
/// primitives via the `rotate_left` method. For example,
Expand Down
6 changes: 6 additions & 0 deletions src/librustc_codegen_llvm/builder.rs
Original file line number Diff line number Diff line change
Expand Up @@ -265,6 +265,12 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
neg(x) => LLVMBuildNeg,
fneg(x) => LLVMBuildFNeg,
not(x) => LLVMBuildNot,
unchecked_sadd(x, y) => LLVMBuildNSWAdd,
unchecked_uadd(x, y) => LLVMBuildNUWAdd,
unchecked_ssub(x, y) => LLVMBuildNSWSub,
unchecked_usub(x, y) => LLVMBuildNUWSub,
unchecked_smul(x, y) => LLVMBuildNSWMul,
unchecked_umul(x, y) => LLVMBuildNUWMul,
}

fn fadd_fast(&mut self, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
Expand Down
24 changes: 23 additions & 1 deletion src/librustc_codegen_llvm/intrinsic.rs
Original file line number Diff line number Diff line change
Expand Up @@ -334,7 +334,8 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
"ctlz" | "ctlz_nonzero" | "cttz" | "cttz_nonzero" | "ctpop" | "bswap" |
"bitreverse" | "add_with_overflow" | "sub_with_overflow" |
"mul_with_overflow" | "overflowing_add" | "overflowing_sub" | "overflowing_mul" |
"unchecked_div" | "unchecked_rem" | "unchecked_shl" | "unchecked_shr" | "exact_div" |
"unchecked_div" | "unchecked_rem" | "unchecked_shl" | "unchecked_shr" |
"unchecked_add" | "unchecked_sub" | "unchecked_mul" | "exact_div" |
"rotate_left" | "rotate_right" | "saturating_add" | "saturating_sub" => {
let ty = arg_tys[0];
match int_type_width_signed(ty, self) {
Expand Down Expand Up @@ -430,6 +431,27 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
} else {
self.lshr(args[0].immediate(), args[1].immediate())
},
"unchecked_add" => {
if signed {
self.unchecked_sadd(args[0].immediate(), args[1].immediate())
} else {
self.unchecked_uadd(args[0].immediate(), args[1].immediate())
}
},
"unchecked_sub" => {
if signed {
self.unchecked_ssub(args[0].immediate(), args[1].immediate())
} else {
self.unchecked_usub(args[0].immediate(), args[1].immediate())
}
},
"unchecked_mul" => {
if signed {
self.unchecked_smul(args[0].immediate(), args[1].immediate())
} else {
self.unchecked_umul(args[0].immediate(), args[1].immediate())
}
},
"rotate_left" | "rotate_right" => {
let is_left = name == "rotate_left";
let val = args[0].immediate();
Expand Down
30 changes: 30 additions & 0 deletions src/librustc_codegen_llvm/llvm/ffi.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1002,6 +1002,36 @@ extern "C" {
RHS: &'a Value,
Name: *const c_char)
-> &'a Value;
pub fn LLVMBuildNSWAdd(B: &Builder<'a>,
LHS: &'a Value,
RHS: &'a Value,
Name: *const c_char)
-> &'a Value;
pub fn LLVMBuildNUWAdd(B: &Builder<'a>,
LHS: &'a Value,
RHS: &'a Value,
Name: *const c_char)
-> &'a Value;
pub fn LLVMBuildNSWSub(B: &Builder<'a>,
LHS: &'a Value,
RHS: &'a Value,
Name: *const c_char)
-> &'a Value;
pub fn LLVMBuildNUWSub(B: &Builder<'a>,
LHS: &'a Value,
RHS: &'a Value,
Name: *const c_char)
-> &'a Value;
pub fn LLVMBuildNSWMul(B: &Builder<'a>,
LHS: &'a Value,
RHS: &'a Value,
Name: *const c_char)
-> &'a Value;
pub fn LLVMBuildNUWMul(B: &Builder<'a>,
LHS: &'a Value,
RHS: &'a Value,
Name: *const c_char)
-> &'a Value;
pub fn LLVMBuildAnd(B: &Builder<'a>,
LHS: &'a Value,
RHS: &'a Value,
Expand Down
6 changes: 6 additions & 0 deletions src/librustc_codegen_ssa/traits/builder.rs
Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,12 @@ pub trait BuilderMethods<'a, 'tcx: 'a>:
fn shl(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn lshr(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn ashr(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn unchecked_sadd(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn unchecked_uadd(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn unchecked_ssub(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn unchecked_usub(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn unchecked_smul(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn unchecked_umul(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn and(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn or(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
fn xor(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
Expand Down
3 changes: 2 additions & 1 deletion src/librustc_typeck/check/intrinsic.rs
Original file line number Diff line number Diff line change
Expand Up @@ -305,7 +305,8 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
"unchecked_shl" | "unchecked_shr" |
"rotate_left" | "rotate_right" =>
(1, vec![param(0), param(0)], param(0)),

"unchecked_add" | "unchecked_sub" | "unchecked_mul" =>
(1, vec![param(0), param(0)], param(0)),
"overflowing_add" | "overflowing_sub" | "overflowing_mul" =>
(1, vec![param(0), param(0)], param(0)),
"saturating_add" | "saturating_sub" =>
Expand Down
46 changes: 46 additions & 0 deletions src/test/codegen/unchecked_math.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,46 @@
#![crate_type = "lib"]
#![feature(core_intrinsics)]

use std::intrinsics::*;

// CHECK-LABEL: @unchecked_add_signed
#[no_mangle]
pub unsafe fn unchecked_add_signed(a: i32, b: i32) -> i32 {
// CHECK: add nsw
unchecked_add(a, b)
}

// CHECK-LABEL: @unchecked_add_unsigned
#[no_mangle]
pub unsafe fn unchecked_add_unsigned(a: u32, b: u32) -> u32 {
// CHECK: add nuw
unchecked_add(a, b)
}

// CHECK-LABEL: @unchecked_sub_signed
#[no_mangle]
pub unsafe fn unchecked_sub_signed(a: i32, b: i32) -> i32 {
// CHECK: sub nsw
unchecked_sub(a, b)
}

// CHECK-LABEL: @unchecked_sub_unsigned
#[no_mangle]
pub unsafe fn unchecked_sub_unsigned(a: u32, b: u32) -> u32 {
// CHECK: sub nuw
unchecked_sub(a, b)
}

// CHECK-LABEL: @unchecked_mul_signed
#[no_mangle]
pub unsafe fn unchecked_mul_signed(a: i32, b: i32) -> i32 {
// CHECK: mul nsw
unchecked_mul(a, b)
}

// CHECK-LABEL: @unchecked_mul_unsigned
#[no_mangle]
pub unsafe fn unchecked_mul_unsigned(a: u32, b: u32) -> u32 {
// CHECK: mul nuw
unchecked_mul(a, b)
}
8 changes: 8 additions & 0 deletions src/test/ui/intrinsics/unchecked_math_unsafe.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
#![feature(core_intrinsics)]

fn main() {
let (x, y) = (1u32, 2u32);
let add = std::intrinsics::unchecked_add(x, y); //~ ERROR call to unsafe function
let sub = std::intrinsics::unchecked_sub(x, y); //~ ERROR call to unsafe function
let mul = std::intrinsics::unchecked_mul(x, y); //~ ERROR call to unsafe function
}
27 changes: 27 additions & 0 deletions src/test/ui/intrinsics/unchecked_math_unsafe.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
--> $DIR/unchecked_math_unsafe.rs:5:15
|
LL | let add = std::intrinsics::unchecked_add(x, y);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
|
= note: consult the function's documentation for information on how to avoid undefined behavior

error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
--> $DIR/unchecked_math_unsafe.rs:6:15
|
LL | let sub = std::intrinsics::unchecked_sub(x, y);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
|
= note: consult the function's documentation for information on how to avoid undefined behavior

error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
--> $DIR/unchecked_math_unsafe.rs:7:15
|
LL | let mul = std::intrinsics::unchecked_mul(x, y);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
|
= note: consult the function's documentation for information on how to avoid undefined behavior

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0133`.
8 changes: 8 additions & 0 deletions src/test/ui/intrinsics/unchecked_math_unstable.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
fn main() {
let (x, y) = (1u32, 2u32);
unsafe {
let add = std::intrinsics::unchecked_add(x, y); //~ ERROR use of unstable library feature
let sub = std::intrinsics::unchecked_sub(x, y); //~ ERROR use of unstable library feature
let mul = std::intrinsics::unchecked_mul(x, y); //~ ERROR use of unstable library feature
}
}
27 changes: 27 additions & 0 deletions src/test/ui/intrinsics/unchecked_math_unstable.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
error[E0658]: use of unstable library feature 'core_intrinsics': intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
--> $DIR/unchecked_math_unstable.rs:4:19
|
LL | let add = std::intrinsics::unchecked_add(x, y);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: add #![feature(core_intrinsics)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'core_intrinsics': intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
--> $DIR/unchecked_math_unstable.rs:5:19
|
LL | let sub = std::intrinsics::unchecked_sub(x, y);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: add #![feature(core_intrinsics)] to the crate attributes to enable

error[E0658]: use of unstable library feature 'core_intrinsics': intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
--> $DIR/unchecked_math_unstable.rs:6:19
|
LL | let mul = std::intrinsics::unchecked_mul(x, y);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: add #![feature(core_intrinsics)] to the crate attributes to enable

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0658`.

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