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Use native scalar fma instruction (#1267)

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Cranelift 0.87 now supports lowering `fma` as a libcall on x86 [0].
With 0.88 enabling the native x86 instruction under the `has_fma` flag.

aarch64 and s390x already support this as a native instruction, so it's
nice that we emit it for those.

We can't lower the SIMD version using the `fma` instruction since the
lowering can fail if the x86 `has_fma` flag is not enabled. Cranelift
doesn't yet know how to fallback for these cases

[0]: 709716bb8e
This commit is contained in:
Afonso Bordado 2022-08-23 11:42:35 +01:00 committed by GitHub
parent 156bda8bc7
commit 48c45c481c
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 12 additions and 12 deletions
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6
src/intrinsics/mod.rs
View File

@ -303,6 +303,12 @@ fn codegen_float_intrinsic_call<'tcx>(
let layout = fx.layout_of(ty);
let res = match intrinsic {
sym::fmaf32 | sym::fmaf64 => {
let a = args[0].load_scalar(fx);
let b = args[1].load_scalar(fx);
let c = args[2].load_scalar(fx);
CValue::by_val(fx.bcx.ins().fma(a, b, c), layout)
}
sym::copysignf32 | sym::copysignf64 => {
let a = args[0].load_scalar(fx);
let b = args[1].load_scalar(fx);

18
src/intrinsics/simd.rs
View File

@ -397,21 +397,15 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
let layout = a.layout();
let (lane_count, lane_ty) = layout.ty.simd_size_and_type(fx.tcx);
let res_lane_layout = fx.layout_of(lane_ty);
for lane in 0..lane_count {
let a_lane = a.value_lane(fx, lane);
let b_lane = b.value_lane(fx, lane);
let c_lane = c.value_lane(fx, lane);
let a_lane = a.value_lane(fx, lane).load_scalar(fx);
let b_lane = b.value_lane(fx, lane).load_scalar(fx);
let c_lane = c.value_lane(fx, lane).load_scalar(fx);
let res_lane = match lane_ty.kind() {
ty::Float(FloatTy::F32) => {
fx.easy_call("fmaf", &[a_lane, b_lane, c_lane], lane_ty)
}
ty::Float(FloatTy::F64) => {
fx.easy_call("fma", &[a_lane, b_lane, c_lane], lane_ty)
}
_ => unreachable!(),
};
let res_lane = fx.bcx.ins().fma(a_lane, b_lane, c_lane);
let res_lane = CValue::by_val(res_lane, res_lane_layout);
ret.place_lane(fx, lane).write_cvalue(fx, res_lane);
}