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Add builtins for f16/f128 float conversions
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beetrees committed Apr 28, 2024
1 parent 2705081 commit efd5d7d
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4 changes: 4 additions & 0 deletions Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,10 @@ c = ["cc"]
# which use inline assembly and fall back to pure Rust versions (if avalible).
no-asm = []

# Workaround for codegen backends which haven't yet implemented `f16` and
# `f128` support. Disabled any intrinsics which use those types.
no-f16-f128 = []

# Flag this library as the unstable compiler-builtins lib
compiler-builtins = []

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61 changes: 33 additions & 28 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -162,7 +162,6 @@ rely on CI.
- [x] divmodsi4.c
- [x] divsf3.c
- [x] divsi3.c
- [ ] extendhfsf2.c
- [x] extendsfdf2.c
- [x] fixdfdi.c
- [x] fixdfsi.c
Expand Down Expand Up @@ -201,9 +200,7 @@ rely on CI.
- [x] powisf2.c
- [x] subdf3.c
- [x] subsf3.c
- [ ] truncdfhf2.c
- [x] truncdfsf2.c
- [ ] truncsfhf2.c
- [x] udivdi3.c
- [x] udivmoddi4.c
- [x] udivmodsi4.c
Expand Down Expand Up @@ -233,60 +230,68 @@ These builtins are needed to support 128-bit integers, which are in the process
- [x] udivti3.c
- [x] umodti3.c

These builtins are needed to support `f16` and `f128`, which are in the process of being added to Rust.

- [ ] addtf3.c
- [ ] comparetf2.c
- [ ] divtf3.c
- [x] extenddftf2.c
- [x] extendhfsf2.c
- [x] extendhftf2.c
- [x] extendsftf2.c
- [ ] fixtfdi.c
- [ ] fixtfsi.c
- [ ] fixtfti.c
- [ ] fixunstfdi.c
- [ ] fixunstfsi.c
- [ ] fixunstfti.c
- [ ] floatditf.c
- [ ] floatsitf.c
- [ ] floatunditf.c
- [ ] floatunsitf.c
- [ ] multf3.c
- [ ] powitf2.c
- [ ] ppc/fixtfdi.c
- [ ] ppc/fixunstfdi.c
- [ ] ppc/floatditf.c
- [ ] ppc/floatunditf.c
- [ ] subtf3.c
- [x] truncdfhf2.c
- [x] truncsfhf2.c
- [x] trunctfdf2.c
- [x] trunctfhf2.c
- [x] trunctfsf2.c

## Unimplemented functions

These builtins involve floating-point types ("`f128`", "`f80`" and complex numbers) that are not supported by Rust.
These builtins involve floating-point types ("`f80`" and complex numbers) that are not supported by Rust.

- ~~addtf3.c~~
- ~~comparetf2.c~~
- ~~divdc3.c~~
- ~~divsc3.c~~
- ~~divtc3.c~~
- ~~divtf3.c~~
- ~~divxc3.c~~
- ~~extenddftf2.c~~
- ~~extendsftf2.c~~
- ~~fixtfdi.c~~
- ~~fixtfsi.c~~
- ~~fixtfti.c~~
- ~~fixunstfdi.c~~
- ~~fixunstfsi.c~~
- ~~fixunstfti.c~~
- ~~fixunsxfdi.c~~
- ~~fixunsxfsi.c~~
- ~~fixunsxfti.c~~
- ~~fixxfdi.c~~
- ~~fixxfti.c~~
- ~~floatditf.c~~
- ~~floatdixf.c~~
- ~~floatsitf.c~~
- ~~floattixf.c~~
- ~~floatunditf.c~~
- ~~floatundixf.c~~
- ~~floatunsitf.c~~
- ~~floatuntixf.c~~
- ~~i386/floatdixf.S~~
- ~~i386/floatundixf.S~~
- ~~muldc3.c~~
- ~~mulsc3.c~~
- ~~multc3.c~~
- ~~multf3.c~~
- ~~mulxc3.c~~
- ~~powitf2.c~~
- ~~powixf2.c~~
- ~~ppc/divtc3.c~~
- ~~ppc/fixtfdi.c~~
- ~~ppc/fixunstfdi.c~~
- ~~ppc/floatditf.c~~
- ~~ppc/floatunditf.c~~
- ~~ppc/gcc_qadd.c~~
- ~~ppc/gcc_qdiv.c~~
- ~~ppc/gcc_qmul.c~~
- ~~ppc/gcc_qsub.c~~
- ~~ppc/multc3.c~~
- ~~subtf3.c~~
- ~~trunctfdf2.c~~
- ~~trunctfsf2.c~~
- ~~x86_64/floatdixf.c~~
- ~~x86_64/floatundixf.S~~

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21 changes: 8 additions & 13 deletions build.rs
Original file line number Diff line number Diff line change
Expand Up @@ -217,6 +217,14 @@ mod c {
}
}

// `compiler-rt` requires `COMPILER_RT_HAS_FLOAT16` to be defined to make it use the
// `_Float16` type for `f16` intrinsics. This shouldn't matter as all existing `f16`
// intrinsics have been ported to Rust in `compiler-builtins` as C compilers don't
// support `_Float16` on all targets (whereas Rust does). However, define the macro
// anyway to prevent issues like rust#118813 and rust#123885 silently reoccuring if more
// `f16` intrinsics get accidentally added here in the future.
cfg.define("COMPILER_RT_HAS_FLOAT16", None);

cfg.warnings(false);

if target_env == "msvc" {
Expand Down Expand Up @@ -288,13 +296,10 @@ mod c {
sources.extend(&[
("__divdc3", "divdc3.c"),
("__divsc3", "divsc3.c"),
("__extendhfsf2", "extendhfsf2.c"),
("__muldc3", "muldc3.c"),
("__mulsc3", "mulsc3.c"),
("__negdf2", "negdf2.c"),
("__negsf2", "negsf2.c"),
("__truncdfhf2", "truncdfhf2.c"),
("__truncsfhf2", "truncsfhf2.c"),
]);
}

Expand Down Expand Up @@ -464,8 +469,6 @@ mod c {
if (target_arch == "aarch64" || target_arch == "arm64ec") && consider_float_intrinsics {
sources.extend(&[
("__comparetf2", "comparetf2.c"),
("__extenddftf2", "extenddftf2.c"),
("__extendsftf2", "extendsftf2.c"),
("__fixtfdi", "fixtfdi.c"),
("__fixtfsi", "fixtfsi.c"),
("__fixtfti", "fixtfti.c"),
Expand All @@ -476,8 +479,6 @@ mod c {
("__floatsitf", "floatsitf.c"),
("__floatunditf", "floatunditf.c"),
("__floatunsitf", "floatunsitf.c"),
("__trunctfdf2", "trunctfdf2.c"),
("__trunctfsf2", "trunctfsf2.c"),
("__addtf3", "addtf3.c"),
("__multf3", "multf3.c"),
("__subtf3", "subtf3.c"),
Expand All @@ -498,7 +499,6 @@ mod c {

if target_arch == "mips64" {
sources.extend(&[
("__extenddftf2", "extenddftf2.c"),
("__netf2", "comparetf2.c"),
("__addtf3", "addtf3.c"),
("__multf3", "multf3.c"),
Expand All @@ -509,14 +509,11 @@ mod c {
("__floatunsitf", "floatunsitf.c"),
("__fe_getround", "fp_mode.c"),
("__divtf3", "divtf3.c"),
("__trunctfdf2", "trunctfdf2.c"),
("__trunctfsf2", "trunctfsf2.c"),
]);
}

if target_arch == "loongarch64" {
sources.extend(&[
("__extenddftf2", "extenddftf2.c"),
("__netf2", "comparetf2.c"),
("__addtf3", "addtf3.c"),
("__multf3", "multf3.c"),
Expand All @@ -527,8 +524,6 @@ mod c {
("__floatunsitf", "floatunsitf.c"),
("__fe_getround", "fp_mode.c"),
("__divtf3", "divtf3.c"),
("__trunctfdf2", "trunctfdf2.c"),
("__trunctfsf2", "trunctfsf2.c"),
]);
}

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4 changes: 4 additions & 0 deletions ci/run.sh
Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,8 @@ else
$run --features c --release
$run --features no-asm
$run --features no-asm --release
$run --features no-f16-f128
$run --features no-f16-f128 --release
fi

if [ -d /builtins-target ]; then
Expand All @@ -45,6 +47,8 @@ cargo build --target "$target" --features c
cargo build --target "$target" --release --features c
cargo build --target "$target" --features no-asm
cargo build --target "$target" --release --features no-asm
cargo build --target "$target" --features no-f16-f128
cargo build --target "$target" --release --features no-f16-f128

PREFIX=${target//unknown-/}-
case "$target" in
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34 changes: 34 additions & 0 deletions src/float/extend.rs
Original file line number Diff line number Diff line change
Expand Up @@ -82,3 +82,37 @@ intrinsics! {
a as f64 // LLVM generate 'fcvtds'
}
}

#[cfg(not(feature = "no-f16-f128"))]
intrinsics! {
#[avr_skip]
#[aapcs_on_arm]
#[arm_aeabi_alias = __aeabi_h2f]
pub extern "C" fn __extendhfsf2(a: f16) -> f32 {
extend(a)
}

#[avr_skip]
#[aapcs_on_arm]
pub extern "C" fn __gnu_h2f_ieee(a: f16) -> f32 {
extend(a)
}

#[avr_skip]
#[aapcs_on_arm]
pub extern "C" fn __extendhftf2(a: f16) -> f128 {
extend(a)
}

#[avr_skip]
#[aapcs_on_arm]
pub extern "C" fn __extendsftf2(a: f32) -> f128 {
extend(a)
}

#[avr_skip]
#[aapcs_on_arm]
pub extern "C" fn __extenddftf2(a: f64) -> f128 {
extend(a)
}
}
19 changes: 18 additions & 1 deletion src/float/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -127,7 +127,20 @@ macro_rules! float_impl {
self.to_bits() as Self::SignedInt
}
fn eq_repr(self, rhs: Self) -> bool {
if self.is_nan() && rhs.is_nan() {
#[cfg(feature = "mangled-names")]
fn is_nan(x: $ty) -> bool {
// When using mangled-names, the "real" compiler-builtins might not have the
// necessary builtin (__unordtf2) to test whether `f128` is NaN.
// FIXME(f16_f128): Remove once the nightly toolchain has the __unordtf2 builtin
// x is NaN if all the bits of the exponent are set and the significand is non-0
x.repr() & $ty::EXPONENT_MASK == $ty::EXPONENT_MASK
&& x.repr() & $ty::SIGNIFICAND_MASK != 0
}
#[cfg(not(feature = "mangled-names"))]
fn is_nan(x: $ty) -> bool {
x.is_nan()
}
if is_nan(self) && is_nan(rhs) {
true
} else {
self.repr() == rhs.repr()
Expand Down Expand Up @@ -171,5 +184,9 @@ macro_rules! float_impl {
};
}

#[cfg(not(feature = "no-f16-f128"))]
float_impl!(f16, u16, i16, i8, 16, 10);
float_impl!(f32, u32, i32, i16, 32, 23);
float_impl!(f64, u64, i64, i16, 64, 52);
#[cfg(not(feature = "no-f16-f128"))]
float_impl!(f128, u128, i128, i16, 128, 112);
55 changes: 51 additions & 4 deletions src/float/trunc.rs
Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,10 @@ where
// destination format. We can convert by simply right-shifting with
// rounding and adjusting the exponent.
abs_result = (a_abs >> sign_bits_delta).cast();
let tmp = src_exp_bias.wrapping_sub(dst_exp_bias) << R::SIGNIFICAND_BITS;
abs_result = abs_result.wrapping_sub(tmp.cast());
// Cast before shifting ro prevent overflow.
let bias_diff: R::Int = src_exp_bias.wrapping_sub(dst_exp_bias).cast();
let tmp = bias_diff << R::SIGNIFICAND_BITS;
abs_result = abs_result.wrapping_sub(tmp);

let round_bits = a_abs & round_mask;
if round_bits > halfway {
Expand All @@ -67,13 +69,17 @@ where
// a is NaN.
// Conjure the result by beginning with infinity, setting the qNaN
// bit and inserting the (truncated) trailing NaN field.
abs_result = (dst_inf_exp << R::SIGNIFICAND_BITS).cast();
// Cast before shifting to prevent overflow.
let dst_inf_exp: R::Int = dst_inf_exp.cast();
abs_result = dst_inf_exp << R::SIGNIFICAND_BITS;
abs_result |= dst_qnan;
abs_result |= dst_nan_code
& ((a_abs & src_nan_code) >> (F::SIGNIFICAND_BITS - R::SIGNIFICAND_BITS)).cast();
} else if a_abs >= overflow {
// a overflows to infinity.
abs_result = (dst_inf_exp << R::SIGNIFICAND_BITS).cast();
// Cast before shifting to prevent overflow.
let dst_inf_exp: R::Int = dst_inf_exp.cast();
abs_result = dst_inf_exp << R::SIGNIFICAND_BITS;
} else {
// a underflows on conversion to the destination type or is an exact
// zero. The result may be a denormal or zero. Extract the exponent
Expand Down Expand Up @@ -124,3 +130,44 @@ intrinsics! {
a as f32
}
}

#[cfg(not(feature = "no-f16-f128"))]
intrinsics! {
#[avr_skip]
#[aapcs_on_arm]
#[arm_aeabi_alias = __aeabi_f2h]
pub extern "C" fn __truncsfhf2(a: f32) -> f16 {
trunc(a)
}

#[avr_skip]
#[aapcs_on_arm]
pub extern "C" fn __gnu_f2h_ieee(a: f32) -> f16 {
trunc(a)
}

#[avr_skip]
#[aapcs_on_arm]
#[arm_aeabi_alias = __aeabi_d2h]
pub extern "C" fn __truncdfhf2(a: f64) -> f16 {
trunc(a)
}

#[avr_skip]
#[aapcs_on_arm]
pub extern "C" fn __trunctfhf2(a: f128) -> f16 {
trunc(a)
}

#[avr_skip]
#[aapcs_on_arm]
pub extern "C" fn __trunctfsf2(a: f128) -> f32 {
trunc(a)
}

#[avr_skip]
#[aapcs_on_arm]
pub extern "C" fn __trunctfdf2(a: f128) -> f64 {
trunc(a)
}
}
2 changes: 2 additions & 0 deletions src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,8 @@
#![feature(naked_functions)]
#![feature(repr_simd)]
#![feature(c_unwind)]
#![cfg_attr(not(feature = "no-f16-f128"), feature(f16))]
#![cfg_attr(not(feature = "no-f16-f128"), feature(f128))]
#![no_builtins]
#![no_std]
#![allow(unused_features)]
Expand Down
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