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work around apfloat bug in FMA by using host floats instead
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@RalfJung
RalfJung committed Aug 6, 2022
1 parent 4208764 commit 5a4ac1e
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Showing 5 changed files with 56 additions and 27 deletions.
18 changes: 9 additions & 9 deletions src/shims/foreign_items.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -588,7 +588,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
let [f] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
// FIXME: Using host floats.
let f = f32::from_bits(this.read_scalar(f)?.to_u32()?);
let f = match link_name.as_str() {
let res = match link_name.as_str() {
"cbrtf" => f.cbrt(),
"coshf" => f.cosh(),
"sinhf" => f.sinh(),
Expand All @@ -598,7 +598,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
"atanf" => f.atan(),
_ => bug!(),
};
this.write_scalar(Scalar::from_u32(f.to_bits()), dest)?;
this.write_scalar(Scalar::from_u32(res.to_bits()), dest)?;
}
#[rustfmt::skip]
| "_hypotf"
Expand All @@ -611,12 +611,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
// FIXME: Using host floats.
let f1 = f32::from_bits(this.read_scalar(f1)?.to_u32()?);
let f2 = f32::from_bits(this.read_scalar(f2)?.to_u32()?);
let n = match link_name.as_str() {
let res = match link_name.as_str() {
"_hypotf" | "hypotf" => f1.hypot(f2),
"atan2f" => f1.atan2(f2),
_ => bug!(),
};
this.write_scalar(Scalar::from_u32(n.to_bits()), dest)?;
this.write_scalar(Scalar::from_u32(res.to_bits()), dest)?;
}
#[rustfmt::skip]
| "cbrt"
Expand All @@ -630,7 +630,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
let [f] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
// FIXME: Using host floats.
let f = f64::from_bits(this.read_scalar(f)?.to_u64()?);
let f = match link_name.as_str() {
let res = match link_name.as_str() {
"cbrt" => f.cbrt(),
"cosh" => f.cosh(),
"sinh" => f.sinh(),
Expand All @@ -640,7 +640,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
"atan" => f.atan(),
_ => bug!(),
};
this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
this.write_scalar(Scalar::from_u64(res.to_bits()), dest)?;
}
#[rustfmt::skip]
| "_hypot"
Expand All @@ -651,12 +651,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
// FIXME: Using host floats.
let f1 = f64::from_bits(this.read_scalar(f1)?.to_u64()?);
let f2 = f64::from_bits(this.read_scalar(f2)?.to_u64()?);
let n = match link_name.as_str() {
let res = match link_name.as_str() {
"_hypot" | "hypot" => f1.hypot(f2),
"atan2" => f1.atan2(f2),
_ => bug!(),
};
this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
this.write_scalar(Scalar::from_u64(res.to_bits()), dest)?;
}
#[rustfmt::skip]
| "_ldexp"
Expand All @@ -668,7 +668,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
let x = this.read_scalar(x)?.to_f64()?;
let exp = this.read_scalar(exp)?.to_i32()?;

// Saturating cast to i16. Even those are outside the valid exponent range to
// Saturating cast to i16. Even those are outside the valid exponent range so
// `scalbn` below will do its over/underflow handling.
let exp = if exp > i32::from(i16::MAX) {
i16::MAX
Expand Down
34 changes: 20 additions & 14 deletions src/shims/intrinsics/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -285,49 +285,55 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
// FIXME: Using host floats.
let f = f32::from_bits(this.read_scalar(f)?.to_u32()?);
let f2 = f32::from_bits(this.read_scalar(f2)?.to_u32()?);
this.write_scalar(Scalar::from_u32(f.powf(f2).to_bits()), dest)?;
let res = f.powf(f2);
this.write_scalar(Scalar::from_u32(res.to_bits()), dest)?;
}

"powf64" => {
let [f, f2] = check_arg_count(args)?;
// FIXME: Using host floats.
let f = f64::from_bits(this.read_scalar(f)?.to_u64()?);
let f2 = f64::from_bits(this.read_scalar(f2)?.to_u64()?);
this.write_scalar(Scalar::from_u64(f.powf(f2).to_bits()), dest)?;
let res = f.powf(f2);
this.write_scalar(Scalar::from_u64(res.to_bits()), dest)?;
}

"fmaf32" => {
let [a, b, c] = check_arg_count(args)?;
let a = this.read_scalar(a)?.to_f32()?;
let b = this.read_scalar(b)?.to_f32()?;
let c = this.read_scalar(c)?.to_f32()?;
let res = a.mul_add(b, c).value;
this.write_scalar(Scalar::from_f32(res), dest)?;
// FIXME: Using host floats, to work around https://github.com/rust-lang/miri/issues/2468.
let a = f32::from_bits(this.read_scalar(a)?.to_u32()?);
let b = f32::from_bits(this.read_scalar(b)?.to_u32()?);
let c = f32::from_bits(this.read_scalar(c)?.to_u32()?);
let res = a.mul_add(b, c);
this.write_scalar(Scalar::from_u32(res.to_bits()), dest)?;
}

"fmaf64" => {
let [a, b, c] = check_arg_count(args)?;
let a = this.read_scalar(a)?.to_f64()?;
let b = this.read_scalar(b)?.to_f64()?;
let c = this.read_scalar(c)?.to_f64()?;
let res = a.mul_add(b, c).value;
this.write_scalar(Scalar::from_f64(res), dest)?;
// FIXME: Using host floats, to work around https://github.com/rust-lang/miri/issues/2468.
let a = f64::from_bits(this.read_scalar(a)?.to_u64()?);
let b = f64::from_bits(this.read_scalar(b)?.to_u64()?);
let c = f64::from_bits(this.read_scalar(c)?.to_u64()?);
let res = a.mul_add(b, c);
this.write_scalar(Scalar::from_u64(res.to_bits()), dest)?;
}

"powif32" => {
let [f, i] = check_arg_count(args)?;
// FIXME: Using host floats.
let f = f32::from_bits(this.read_scalar(f)?.to_u32()?);
let i = this.read_scalar(i)?.to_i32()?;
this.write_scalar(Scalar::from_u32(f.powi(i).to_bits()), dest)?;
let res = f.powi(i);
this.write_scalar(Scalar::from_u32(res.to_bits()), dest)?;
}

"powif64" => {
let [f, i] = check_arg_count(args)?;
// FIXME: Using host floats.
let f = f64::from_bits(this.read_scalar(f)?.to_u64()?);
let i = this.read_scalar(i)?.to_i32()?;
this.write_scalar(Scalar::from_u64(f.powi(i).to_bits()), dest)?;
let res = f.powi(i);
this.write_scalar(Scalar::from_u64(res.to_bits()), dest)?;
}

"float_to_int_unchecked" => {
Expand Down
19 changes: 15 additions & 4 deletions src/shims/intrinsics/simd.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -238,14 +238,25 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
let dest = this.mplace_index(&dest, i)?;

// Works for f32 and f64.
// FIXME: using host floats to work around https://github.com/rust-lang/miri/issues/2468.
let ty::Float(float_ty) = dest.layout.ty.kind() else {
span_bug!(this.cur_span(), "{} operand is not a float", intrinsic_name)
};
let val = match float_ty {
FloatTy::F32 =>
Scalar::from_f32(a.to_f32()?.mul_add(b.to_f32()?, c.to_f32()?).value),
FloatTy::F64 =>
Scalar::from_f64(a.to_f64()?.mul_add(b.to_f64()?, c.to_f64()?).value),
FloatTy::F32 => {
let a = f32::from_bits(a.to_u32()?);
let b = f32::from_bits(b.to_u32()?);
let c = f32::from_bits(c.to_u32()?);
let res = a.mul_add(b, c);
Scalar::from_u32(res.to_bits())
}
FloatTy::F64 => {
let a = f64::from_bits(a.to_u64()?);
let b = f64::from_bits(b.to_u64()?);
let c = f64::from_bits(c.to_u64()?);
let res = a.mul_add(b, c);
Scalar::from_u64(res.to_bits())
}
};
this.write_scalar(val, &dest.into())?;
}
Expand Down
2 changes: 2 additions & 0 deletions tests/pass/intrinsics-math.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,8 @@ pub fn main() {
assert_eq!(0.0f32.mul_add(-2.0, f32::consts::E), f32::consts::E);
assert_approx_eq!(3.0f64.mul_add(2.0, 5.0), 11.0);
assert_eq!(0.0f64.mul_add(-2.0f64, f64::consts::E), f64::consts::E);
assert_eq!((-3.2f32).mul_add(2.4, f32::NEG_INFINITY), f32::NEG_INFINITY);
assert_eq!((-3.2f64).mul_add(2.4, f64::NEG_INFINITY), f64::NEG_INFINITY);

assert_approx_eq!((-1.0f32).abs(), 1.0f32);
assert_approx_eq!(34.2f64.abs(), 34.2f64);
Expand Down
10 changes: 10 additions & 0 deletions tests/pass/portable-simd.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,11 @@ fn simd_ops_f32() {

assert_eq!(a.mul_add(b, a), (a * b) + a);
assert_eq!(b.mul_add(b, a), (b * b) + a);
assert_eq!(a.mul_add(b, b), (a * b) + b);
assert_eq!(
f32x4::splat(-3.2).mul_add(b, f32x4::splat(f32::NEG_INFINITY)),
f32x4::splat(f32::NEG_INFINITY)
);
assert_eq!((a * a).sqrt(), a);
assert_eq!((b * b).sqrt(), b.abs());

Expand Down Expand Up @@ -67,6 +72,11 @@ fn simd_ops_f64() {

assert_eq!(a.mul_add(b, a), (a * b) + a);
assert_eq!(b.mul_add(b, a), (b * b) + a);
assert_eq!(a.mul_add(b, b), (a * b) + b);
assert_eq!(
f64x4::splat(-3.2).mul_add(b, f64x4::splat(f64::NEG_INFINITY)),
f64x4::splat(f64::NEG_INFINITY)
);
assert_eq!((a * a).sqrt(), a);
assert_eq!((b * b).sqrt(), b.abs());

Expand Down

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