Support f16 and f128 #1461

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1. bjorn3 commented on Mar 1, 2024

   

   bjorn3

   on Mar 1, 2024

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   This will need direct Cranelift support. Back ib the day before Cranelift had native 128bit int support I had a whole bunch of hacks to make it work. They were really fragile and I don't think they will work anymore for the current structure of cg_clif.
2. tgross35 commented on Mar 5, 2024

   

   tgross35

   on Mar 5, 2024

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   What all would be needed for clif to support these in a minimal state?
3. bjorn3 commented on Mar 5, 2024

   

   bjorn3

   on Mar 5, 2024

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   At a minimum Cranelift support for the f16 and f128 values. And either Cranelift support for float instructions for these types or emulation in cg_clif using libm calls in

   rustc_codegen_cranelift/src/num.rs

   Lines 313 to 363 in 8c46d93

   	pub(crate) fn codegen_float_binop<'tcx>(
   	fx: &mut FunctionCx<'_, '_, 'tcx>,
   	bin_op: BinOp,
   	in_lhs: CValue<'tcx>,
   	in_rhs: CValue<'tcx>,
   	) -> CValue<'tcx> {
   	assert_eq!(in_lhs.layout().ty, in_rhs.layout().ty);
   	let lhs = in_lhs.load_scalar(fx);
   	let rhs = in_rhs.load_scalar(fx);
   	let b = fx.bcx.ins();
   	let res = match bin_op {
   	BinOp::Add => b.fadd(lhs, rhs),
   	BinOp::Sub => b.fsub(lhs, rhs),
   	BinOp::Mul => b.fmul(lhs, rhs),
   	BinOp::Div => b.fdiv(lhs, rhs),
   	BinOp::Rem => {
   	let (name, ty) = match in_lhs.layout().ty.kind() {
   	ty::Float(FloatTy::F32) => ("fmodf", types::F32),
   	ty::Float(FloatTy::F64) => ("fmod", types::F64),
   	_ => bug!(),
   	};
   	let ret_val = fx.lib_call(
   	name,
   	vec![AbiParam::new(ty), AbiParam::new(ty)],
   	vec![AbiParam::new(ty)],
   	&[lhs, rhs],
   	)[0];
   	return CValue::by_val(ret_val, in_lhs.layout());
   	}
   	BinOp::Eq | BinOp::Lt | BinOp::Le | BinOp::Ne | BinOp::Ge | BinOp::Gt => {
   	let fltcc = match bin_op {
   	BinOp::Eq => FloatCC::Equal,
   	BinOp::Lt => FloatCC::LessThan,
   	BinOp::Le => FloatCC::LessThanOrEqual,
   	BinOp::Ne => FloatCC::NotEqual,
   	BinOp::Ge => FloatCC::GreaterThanOrEqual,
   	BinOp::Gt => FloatCC::GreaterThan,
   	_ => unreachable!(),
   	};
   	let val = fx.bcx.ins().fcmp(fltcc, lhs, rhs);
   	return CValue::by_val(val, fx.layout_of(fx.tcx.types.bool));
   	}
   	_ => unreachable!("{:?}({:?}, {:?})", bin_op, in_lhs, in_rhs),
   	};
   	CValue::by_val(res, in_lhs.layout())
   	}

   and

   rustc_codegen_cranelift/src/intrinsics/mod.rs

   Lines 309 to 349 in 8c46d93

   	let (name, arg_count, ty, clif_ty) = match intrinsic {
   	sym::expf32 => ("expf", 1, fx.tcx.types.f32, types::F32),
   	sym::expf64 => ("exp", 1, fx.tcx.types.f64, types::F64),
   	sym::exp2f32 => ("exp2f", 1, fx.tcx.types.f32, types::F32),
   	sym::exp2f64 => ("exp2", 1, fx.tcx.types.f64, types::F64),
   	sym::sqrtf32 => ("sqrtf", 1, fx.tcx.types.f32, types::F32),
   	sym::sqrtf64 => ("sqrt", 1, fx.tcx.types.f64, types::F64),
   	sym::powif32 => ("__powisf2", 2, fx.tcx.types.f32, types::F32), // compiler-builtins
   	sym::powif64 => ("__powidf2", 2, fx.tcx.types.f64, types::F64), // compiler-builtins
   	sym::powf32 => ("powf", 2, fx.tcx.types.f32, types::F32),
   	sym::powf64 => ("pow", 2, fx.tcx.types.f64, types::F64),
   	sym::logf32 => ("logf", 1, fx.tcx.types.f32, types::F32),
   	sym::logf64 => ("log", 1, fx.tcx.types.f64, types::F64),
   	sym::log2f32 => ("log2f", 1, fx.tcx.types.f32, types::F32),
   	sym::log2f64 => ("log2", 1, fx.tcx.types.f64, types::F64),
   	sym::log10f32 => ("log10f", 1, fx.tcx.types.f32, types::F32),
   	sym::log10f64 => ("log10", 1, fx.tcx.types.f64, types::F64),
   	sym::fabsf32 => ("fabsf", 1, fx.tcx.types.f32, types::F32),
   	sym::fabsf64 => ("fabs", 1, fx.tcx.types.f64, types::F64),
   	sym::fmaf32 => ("fmaf", 3, fx.tcx.types.f32, types::F32),
   	sym::fmaf64 => ("fma", 3, fx.tcx.types.f64, types::F64),
   	sym::copysignf32 => ("copysignf", 2, fx.tcx.types.f32, types::F32),
   	sym::copysignf64 => ("copysign", 2, fx.tcx.types.f64, types::F64),
   	sym::floorf32 => ("floorf", 1, fx.tcx.types.f32, types::F32),
   	sym::floorf64 => ("floor", 1, fx.tcx.types.f64, types::F64),
   	sym::ceilf32 => ("ceilf", 1, fx.tcx.types.f32, types::F32),
   	sym::ceilf64 => ("ceil", 1, fx.tcx.types.f64, types::F64),
   	sym::truncf32 => ("truncf", 1, fx.tcx.types.f32, types::F32),
   	sym::truncf64 => ("trunc", 1, fx.tcx.types.f64, types::F64),
   	sym::rintf32 => ("rintf", 1, fx.tcx.types.f32, types::F32),
   	sym::rintf64 => ("rint", 1, fx.tcx.types.f64, types::F64),
   	sym::roundf32 => ("roundf", 1, fx.tcx.types.f32, types::F32),
   	sym::roundf64 => ("round", 1, fx.tcx.types.f64, types::F64),
   	sym::roundevenf32 => ("roundevenf", 1, fx.tcx.types.f32, types::F32),
   	sym::roundevenf64 => ("roundeven", 1, fx.tcx.types.f64, types::F64),
   	sym::sinf32 => ("sinf", 1, fx.tcx.types.f32, types::F32),
   	sym::sinf64 => ("sin", 1, fx.tcx.types.f64, types::F64),
   	sym::cosf32 => ("cosf", 1, fx.tcx.types.f32, types::F32),
   	sym::cosf64 => ("cos", 1, fx.tcx.types.f64, types::F64),
   	_ => return false,
   	};

   .
4. bjorn3

   added

   C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.

   on May 12, 2024
5. Nemo157 commented on Oct 25, 2024

   

   Nemo157

   on Oct 25, 2024

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   It seems like the frontend is now hooked up and this is used in some sysroot crates like compiler-builtins so using -Zbuild-std with cranelift fails, is there some way to avoid this now?
6. tgross35 commented on Oct 25, 2024

   

   tgross35

   on Oct 25, 2024

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   compiler-builtins has the no-f16-f128 feature to disable both of these https://github.com/rust-lang/compiler-builtins/blob/adaef3265c560998a03b6902bd63d88009d3a132/Cargo.toml#L55, and then std carries a flag to propagate that https://github.com/rust-lang/rust/blob/017ae1b21f7be6dcdcfc95631e54bde806653a8a/library/std/Cargo.toml#L103. Maybe there is a way to automatically set this flag based on codegen backend in build-std?
7. Nemo157 commented on Oct 25, 2024

   

   Nemo157

   on Oct 25, 2024

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   Ah yes, I'd found the compiler-builtins feature but missed the std one, this works now:

   export CARGO_UNSTABLE_BUILD_STD_FEATURES=compiler-builtins-no-f16-f128
   export CARGO_UNSTABLE_BUILD_STD=std,panic_abort
   

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8. bjorn3

   closed this as completedin #1574on May 24, 2025