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japaricjaparic
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omit bounds check in release mode
this eliminates panicking branches in the optimized version of the functions. We keep the bounds checks when running the test suite to check that we never do an out of bounds access. This commit also adds a "must link" test that ensures that future changes in our implementation won't add panicking branches. closes rust-lang#129
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7 files changed

+233
-52
lines changed

7 files changed

+233
-52
lines changed

‎Cargo.toml

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Original file line numberDiff line numberDiff line change
@@ -9,5 +9,9 @@ name = "libm"
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repository = "https://github.com/japaric/libm"
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version = "0.1.2"
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[features]
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# only used to run our test suite
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checked = []
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[workspace]
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members = ["cb", "test-generator"]

‎ci/script.sh

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -12,11 +12,21 @@ main() {
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# check that we can source import libm into compiler-builtins
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cargo check --package cb
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# test that the functions don't contain invocations of `panic!`
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case $TARGET in
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armv7-unknown-linux-gnueabihf)
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cross build --release --target $TARGET --example no-panic
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;;
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esac
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# run unit tests
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cross test --lib --features checked --target $TARGET --release
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# generate tests
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cargo run --package test-generator --target x86_64-unknown-linux-musl
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# run tests
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cross test --target $TARGET --release
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# run generated tests
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cross test --tests --features checked --target $TARGET --release
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# TODO need to fix overflow issues (cf. issue #4)
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# cross test --target $TARGET

‎examples/no-panic.rs

Lines changed: 115 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,115 @@
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#![feature(lang_items)]
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#![feature(panic_implementation)]
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#![no_main]
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#![no_std]
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extern crate libm;
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use core::panic::PanicInfo;
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use core::ptr;
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macro_rules! force_eval {
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($e:expr) => {
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unsafe {
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core::ptr::read_volatile(&$e);
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}
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};
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}
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#[no_mangle]
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pub fn main() {
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force_eval!(libm::acos(random()));
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force_eval!(libm::acosf(random()));
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force_eval!(libm::asin(random()));
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force_eval!(libm::asinf(random()));
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force_eval!(libm::atan(random()));
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force_eval!(libm::atan2(random(), random()));
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force_eval!(libm::atan2f(random(), random()));
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force_eval!(libm::atanf(random()));
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force_eval!(libm::cbrt(random()));
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force_eval!(libm::cbrtf(random()));
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force_eval!(libm::ceil(random()));
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force_eval!(libm::ceilf(random()));
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force_eval!(libm::cos(random()));
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force_eval!(libm::cosf(random()));
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force_eval!(libm::cosh(random()));
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force_eval!(libm::coshf(random()));
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force_eval!(libm::exp(random()));
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force_eval!(libm::exp2(random()));
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force_eval!(libm::exp2f(random()));
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force_eval!(libm::expf(random()));
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force_eval!(libm::expm1(random()));
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force_eval!(libm::expm1f(random()));
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force_eval!(libm::fabs(random()));
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force_eval!(libm::fabsf(random()));
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force_eval!(libm::fdim(random(), random()));
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force_eval!(libm::fdimf(random(), random()));
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force_eval!(libm::floor(random()));
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force_eval!(libm::floorf(random()));
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force_eval!(libm::fma(random(), random(), random()));
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force_eval!(libm::fmaf(random(), random(), random()));
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force_eval!(libm::fmod(random(), random()));
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force_eval!(libm::fmodf(random(), random()));
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force_eval!(libm::hypot(random(), random()));
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force_eval!(libm::hypotf(random(), random()));
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force_eval!(libm::log(random()));
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force_eval!(libm::log2(random()));
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force_eval!(libm::log10(random()));
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force_eval!(libm::log10f(random()));
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force_eval!(libm::log1p(random()));
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force_eval!(libm::log1pf(random()));
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force_eval!(libm::log2f(random()));
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force_eval!(libm::logf(random()));
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force_eval!(libm::pow(random(), random()));
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force_eval!(libm::powf(random(), random()));
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force_eval!(libm::round(random()));
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force_eval!(libm::roundf(random()));
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force_eval!(libm::scalbn(random(), random()));
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force_eval!(libm::scalbnf(random(), random()));
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force_eval!(libm::sin(random()));
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force_eval!(libm::sinf(random()));
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force_eval!(libm::sinh(random()));
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force_eval!(libm::sinhf(random()));
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force_eval!(libm::sqrt(random()));
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force_eval!(libm::sqrtf(random()));
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force_eval!(libm::tan(random()));
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force_eval!(libm::tanf(random()));
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force_eval!(libm::tanh(random()));
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force_eval!(libm::tanhf(random()));
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force_eval!(libm::trunc(random()));
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force_eval!(libm::truncf(random()));
81+
}
82+
83+
fn random<T>() -> T
84+
where
85+
T: Copy,
86+
{
87+
unsafe {
88+
static mut X: usize = 0;
89+
X += 8;
90+
ptr::read_volatile(X as *const T)
91+
}
92+
}
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#[panic_implementation]
95+
#[no_mangle]
96+
pub fn panic(_info: &PanicInfo) -> ! {
97+
// loop {}
98+
extern "C" {
99+
fn thou_shalt_not_panic() -> !;
100+
}
101+
102+
unsafe { thou_shalt_not_panic() }
103+
}
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#[link(name = "c")]
106+
extern "C" {}
107+
108+
#[lang = "eh_personality"]
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fn eh() {}
110+
111+
#[no_mangle]
112+
pub extern "C" fn __aeabi_unwind_cpp_pr0() {}
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#[no_mangle]
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pub extern "C" fn __aeabi_unwind_cpp_pr1() {}

‎src/math/atan.rs

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -124,7 +124,7 @@ pub fn atan(x: f64) -> f64 {
124124
return x - x * (s1 + s2);
125125
}
126126

127-
let z = ATANHI[id as usize] - (x * (s1 + s2) - ATANLO[id as usize] - x);
127+
let z = i!(ATANHI, id as usize) - (x * (s1 + s2) - i!(ATANLO, id as usize) - x);
128128

129129
if sign != 0 {
130130
-z

‎src/math/mod.rs

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Original file line numberDiff line numberDiff line change
@@ -6,6 +6,50 @@ macro_rules! force_eval {
66
};
77
}
88

9+
#[cfg(not(feature = "checked"))]
10+
macro_rules! i {
11+
($array:expr, $index:expr) => {
12+
unsafe { *$array.get_unchecked($index) }
13+
};
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($array:expr, $index:expr, =, $rhs:expr) => {
15+
unsafe { *$array.get_unchecked_mut($index) = $rhs; }
16+
};
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($array:expr, $index:expr, +=, $rhs:expr) => {
18+
unsafe { *$array.get_unchecked_mut($index) += $rhs; }
19+
};
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($array:expr, $index:expr, -=, $rhs:expr) => {
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unsafe { *$array.get_unchecked_mut($index) -= $rhs; }
22+
};
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($array:expr, $index:expr, &=, $rhs:expr) => {
24+
unsafe { *$array.get_unchecked_mut($index) &= $rhs; }
25+
};
26+
($array:expr, $index:expr, ==, $rhs:expr) => {
27+
unsafe { *$array.get_unchecked_mut($index) == $rhs }
28+
};
29+
}
30+
31+
#[cfg(feature = "checked")]
32+
macro_rules! i {
33+
($array:expr, $index:expr) => {
34+
*$array.get($index).unwrap()
35+
};
36+
($array:expr, $index:expr, =, $rhs:expr) => {
37+
*$array.get_mut($index).unwrap() = $rhs;
38+
};
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($array:expr, $index:expr, -=, $rhs:expr) => {
40+
*$array.get_mut($index).unwrap() -= $rhs;
41+
};
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($array:expr, $index:expr, +=, $rhs:expr) => {
43+
*$array.get_mut($index).unwrap() += $rhs;
44+
};
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($array:expr, $index:expr, &=, $rhs:expr) => {
46+
*$array.get_mut($index).unwrap() &= $rhs;
47+
};
48+
($array:expr, $index:expr, ==, $rhs:expr) => {
49+
*$array.get_mut($index).unwrap() == $rhs
50+
};
51+
}
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// Public modules
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mod acos;
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mod acosf;

‎src/math/rem_pio2.rs

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Original file line numberDiff line numberDiff line change
@@ -177,7 +177,7 @@ pub fn rem_pio2(x: f64) -> (i32, f64, f64) {
177177
tx[2] = z;
178178
/* skip zero terms, first term is non-zero */
179179
let mut i = 2;
180-
while tx[i] == 0.0 {
180+
while i != 0 && tx[i] == 0.0 {
181181
i -= 1;
182182
}
183183
let mut ty = [0.0; 3];

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