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Auto merge of #902 - RalfJung:ldexp, r=RalfJung

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use apfloat for ldexp
This commit is contained in:
bors 2019-08-10 09:34:31 +00:00
commit a5eb61a4ad
2 changed files with 31 additions and 14 deletions
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31
src/shims/foreign_items.rs
View file

@ -1,3 +1,6 @@
use std::convert::TryInto;
use rustc_apfloat::Float;
use rustc::ty::layout::{Align, LayoutOf, Size};
use rustc::hir::def_id::DefId;
use rustc::mir;
@ -577,7 +580,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
};
this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
}
// underscore case for windows
// underscore case for windows, here and below
// (see https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/floating-point-primitives?view=vs-2019)
"_hypot" | "hypot" | "atan2" => {
// FIXME: Using host floats.
let f1 = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
@ -589,16 +593,23 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
};
this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
}
// underscore case for windows
"_ldexp" | "ldexp" => {
// FIXME: Using host floats.
let x = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
// For radix-2 (binary) systems, `ldexp` and `scalbn` are the same.
"_ldexp" | "ldexp" | "scalbn" => {
let x = this.read_scalar(args[0])?.to_f64()?;
let exp = this.read_scalar(args[1])?.to_i32()?;
extern {
fn ldexp(x: f64, n: i32) -> f64;
}
let n = unsafe { ldexp(x, exp) };
this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
// Saturating cast to i16. Even those are outside the valid exponent range to
// `scalbn` below will do its over/underflow handling.
let exp = if exp > i16::max_value() as i32 {
i16::max_value()
} else if exp < i16::min_value() as i32 {
i16::min_value()
} else {
exp.try_into().unwrap()
};
let res = x.scalbn(exp);
this.write_scalar(Scalar::from_f64(res), dest)?;
}
// Some things needed for `sys::thread` initialization to go through.

14
tests/run-pass/intrinsics-math.rs
View file

@ -16,6 +16,13 @@ macro_rules! assert_approx_eq {
})
}
fn ldexp(a: f64, b: i32) -> f64 {
extern {
fn ldexp(x: f64, n: i32) -> f64;
}
unsafe { ldexp(a, b) }
}
pub fn main() {
use std::f32;
use std::f64;
@ -88,8 +95,7 @@ pub fn main() {
assert_eq!(3.3_f32.round(), 3.0);
assert_eq!(3.3_f64.round(), 3.0);
extern {
fn ldexp(x: f64, n: i32) -> f64;
}
unsafe { assert_approx_eq!(ldexp(0.65f64, 3i32), 5.2f64); }
assert_eq!(ldexp(0.65f64, 3i32), 5.2f64);
assert_eq!(ldexp(1.42, 0xFFFF), f64::INFINITY);
assert_eq!(ldexp(1.42, -0xFFFF), 0f64);
}