1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356
use rustc_apfloat::{ieee::Single, Float as _};
use rustc_middle::mir;
use rustc_span::Symbol;
use rustc_target::spec::abi::Abi;
use rand::Rng as _;
use super::{bin_op_simd_float_all, bin_op_simd_float_first, FloatBinOp, FloatCmpOp};
use crate::*;
use shims::foreign_items::EmulateByNameResult;
impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {}
pub(super) trait EvalContextExt<'mir, 'tcx: 'mir>:
crate::MiriInterpCxExt<'mir, 'tcx>
{
fn emulate_x86_sse_intrinsic(
&mut self,
link_name: Symbol,
abi: Abi,
args: &[OpTy<'tcx, Provenance>],
dest: &PlaceTy<'tcx, Provenance>,
) -> InterpResult<'tcx, EmulateByNameResult<'mir, 'tcx>> {
let this = self.eval_context_mut();
// Prefix should have already been checked.
let unprefixed_name = link_name.as_str().strip_prefix("llvm.x86.sse.").unwrap();
// All these intrinsics operate on 128-bit (f32x4) SIMD vectors unless stated otherwise.
// Many intrinsic names are sufixed with "ps" (packed single) or "ss" (scalar single),
// where single means single precision floating point (f32). "ps" means thet the operation
// is performed on each element of the vector, while "ss" means that the operation is
// performed only on the first element, copying the remaining elements from the input
// vector (for binary operations, from the left-hand side).
match unprefixed_name {
// Used to implement _mm_{add,sub,mul,div,min,max}_ss functions.
// Performs the operations on the first component of `left` and
// `right` and copies the remaining components from `left`.
"add.ss" | "sub.ss" | "mul.ss" | "div.ss" | "min.ss" | "max.ss" => {
let [left, right] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let which = match unprefixed_name {
"add.ss" => FloatBinOp::Arith(mir::BinOp::Add),
"sub.ss" => FloatBinOp::Arith(mir::BinOp::Sub),
"mul.ss" => FloatBinOp::Arith(mir::BinOp::Mul),
"div.ss" => FloatBinOp::Arith(mir::BinOp::Div),
"min.ss" => FloatBinOp::Min,
"max.ss" => FloatBinOp::Max,
_ => unreachable!(),
};
bin_op_simd_float_first::<Single>(this, which, left, right, dest)?;
}
// Used to implement _mm_min_ps and _mm_max_ps functions.
// Note that the semantics are a bit different from Rust simd_min
// and simd_max intrinsics regarding handling of NaN and -0.0: Rust
// matches the IEEE min/max operations, while x86 has different
// semantics.
"min.ps" | "max.ps" => {
let [left, right] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let which = match unprefixed_name {
"min.ps" => FloatBinOp::Min,
"max.ps" => FloatBinOp::Max,
_ => unreachable!(),
};
bin_op_simd_float_all::<Single>(this, which, left, right, dest)?;
}
// Used to implement _mm_{sqrt,rcp,rsqrt}_ss functions.
// Performs the operations on the first component of `op` and
// copies the remaining components from `op`.
"sqrt.ss" | "rcp.ss" | "rsqrt.ss" => {
let [op] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let which = match unprefixed_name {
"sqrt.ss" => FloatUnaryOp::Sqrt,
"rcp.ss" => FloatUnaryOp::Rcp,
"rsqrt.ss" => FloatUnaryOp::Rsqrt,
_ => unreachable!(),
};
unary_op_ss(this, which, op, dest)?;
}
// Used to implement _mm_{sqrt,rcp,rsqrt}_ps functions.
// Performs the operations on all components of `op`.
"sqrt.ps" | "rcp.ps" | "rsqrt.ps" => {
let [op] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let which = match unprefixed_name {
"sqrt.ps" => FloatUnaryOp::Sqrt,
"rcp.ps" => FloatUnaryOp::Rcp,
"rsqrt.ps" => FloatUnaryOp::Rsqrt,
_ => unreachable!(),
};
unary_op_ps(this, which, op, dest)?;
}
// Used to implement the _mm_cmp_ss function.
// Performs a comparison operation on the first component of `left`
// and `right`, returning 0 if false or `u32::MAX` if true. The remaining
// components are copied from `left`.
"cmp.ss" => {
let [left, right, imm] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let which = FloatBinOp::Cmp(FloatCmpOp::from_intrinsic_imm(
this.read_scalar(imm)?.to_i8()?,
"llvm.x86.sse.cmp.ss",
)?);
bin_op_simd_float_first::<Single>(this, which, left, right, dest)?;
}
// Used to implement the _mm_cmp_ps function.
// Performs a comparison operation on each component of `left`
// and `right`. For each component, returns 0 if false or u32::MAX
// if true.
"cmp.ps" => {
let [left, right, imm] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let which = FloatBinOp::Cmp(FloatCmpOp::from_intrinsic_imm(
this.read_scalar(imm)?.to_i8()?,
"llvm.x86.sse.cmp.ps",
)?);
bin_op_simd_float_all::<Single>(this, which, left, right, dest)?;
}
// Used to implement _mm_{,u}comi{eq,lt,le,gt,ge,neq}_ss functions.
// Compares the first component of `left` and `right` and returns
// a scalar value (0 or 1).
"comieq.ss" | "comilt.ss" | "comile.ss" | "comigt.ss" | "comige.ss" | "comineq.ss"
| "ucomieq.ss" | "ucomilt.ss" | "ucomile.ss" | "ucomigt.ss" | "ucomige.ss"
| "ucomineq.ss" => {
let [left, right] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let (left, left_len) = this.operand_to_simd(left)?;
let (right, right_len) = this.operand_to_simd(right)?;
assert_eq!(left_len, right_len);
let left = this.read_scalar(&this.project_index(&left, 0)?)?.to_f32()?;
let right = this.read_scalar(&this.project_index(&right, 0)?)?.to_f32()?;
// The difference between the com* and *ucom variants is signaling
// of exceptions when either argument is a quiet NaN. We do not
// support accessing the SSE status register from miri (or from Rust,
// for that matter), so we treat equally both variants.
let res = match unprefixed_name {
"comieq.ss" | "ucomieq.ss" => left == right,
"comilt.ss" | "ucomilt.ss" => left < right,
"comile.ss" | "ucomile.ss" => left <= right,
"comigt.ss" | "ucomigt.ss" => left > right,
"comige.ss" | "ucomige.ss" => left >= right,
"comineq.ss" | "ucomineq.ss" => left != right,
_ => unreachable!(),
};
this.write_scalar(Scalar::from_i32(i32::from(res)), dest)?;
}
// Use to implement the _mm_cvtss_si32, _mm_cvttss_si32,
// _mm_cvtss_si64 and _mm_cvttss_si64 functions.
// Converts the first component of `op` from f32 to i32/i64.
"cvtss2si" | "cvttss2si" | "cvtss2si64" | "cvttss2si64" => {
let [op] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let (op, _) = this.operand_to_simd(op)?;
let op = this.read_scalar(&this.project_index(&op, 0)?)?.to_f32()?;
let rnd = match unprefixed_name {
// "current SSE rounding mode", assume nearest
// https://www.felixcloutier.com/x86/cvtss2si
"cvtss2si" | "cvtss2si64" => rustc_apfloat::Round::NearestTiesToEven,
// always truncate
// https://www.felixcloutier.com/x86/cvttss2si
"cvttss2si" | "cvttss2si64" => rustc_apfloat::Round::TowardZero,
_ => unreachable!(),
};
let res = this.float_to_int_checked(op, dest.layout, rnd).unwrap_or_else(|| {
// Fallback to minimum acording to SSE semantics.
ImmTy::from_int(dest.layout.size.signed_int_min(), dest.layout)
});
this.write_immediate(*res, dest)?;
}
// Used to implement the _mm_cvtsi32_ss and _mm_cvtsi64_ss functions.
// Converts `right` from i32/i64 to f32. Returns a SIMD vector with
// the result in the first component and the remaining components
// are copied from `left`.
// https://www.felixcloutier.com/x86/cvtsi2ss
"cvtsi2ss" | "cvtsi642ss" => {
let [left, right] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let (left, left_len) = this.operand_to_simd(left)?;
let (dest, dest_len) = this.place_to_simd(dest)?;
assert_eq!(dest_len, left_len);
let right = this.read_immediate(right)?;
let dest0 = this.project_index(&dest, 0)?;
let res0 = this.int_to_int_or_float(&right, dest0.layout)?;
this.write_immediate(*res0, &dest0)?;
for i in 1..dest_len {
this.copy_op(
&this.project_index(&left, i)?,
&this.project_index(&dest, i)?,
/*allow_transmute*/ false,
)?;
}
}
// Used to implement the _mm_movemask_ps function.
// Returns a scalar integer where the i-th bit is the highest
// bit of the i-th component of `op`.
// https://www.felixcloutier.com/x86/movmskps
"movmsk.ps" => {
let [op] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let (op, op_len) = this.operand_to_simd(op)?;
let mut res = 0;
for i in 0..op_len {
let op = this.read_scalar(&this.project_index(&op, i)?)?;
let op = op.to_u32()?;
// Extract the highest bit of `op` and place it in the `i`-th bit of `res`
res |= (op >> 31) << i;
}
this.write_scalar(Scalar::from_u32(res), dest)?;
}
_ => return Ok(EmulateByNameResult::NotSupported),
}
Ok(EmulateByNameResult::NeedsJumping)
}
}
#[derive(Copy, Clone)]
enum FloatUnaryOp {
/// sqrt(x)
///
/// <https://www.felixcloutier.com/x86/sqrtss>
/// <https://www.felixcloutier.com/x86/sqrtps>
Sqrt,
/// Approximation of 1/x
///
/// <https://www.felixcloutier.com/x86/rcpss>
/// <https://www.felixcloutier.com/x86/rcpps>
Rcp,
/// Approximation of 1/sqrt(x)
///
/// <https://www.felixcloutier.com/x86/rsqrtss>
/// <https://www.felixcloutier.com/x86/rsqrtps>
Rsqrt,
}
/// Performs `which` scalar operation on `op` and returns the result.
#[allow(clippy::arithmetic_side_effects)] // floating point operations without side effects
fn unary_op_f32<'tcx>(
this: &mut crate::MiriInterpCx<'_, 'tcx>,
which: FloatUnaryOp,
op: &ImmTy<'tcx, Provenance>,
) -> InterpResult<'tcx, Scalar<Provenance>> {
match which {
FloatUnaryOp::Sqrt => {
let op = op.to_scalar();
// FIXME using host floats
Ok(Scalar::from_u32(f32::from_bits(op.to_u32()?).sqrt().to_bits()))
}
FloatUnaryOp::Rcp => {
let op = op.to_scalar().to_f32()?;
let div = (Single::from_u128(1).value / op).value;
// Apply a relative error with a magnitude on the order of 2^-12 to simulate the
// inaccuracy of RCP.
let res = apply_random_float_error(this, div, -12);
Ok(Scalar::from_f32(res))
}
FloatUnaryOp::Rsqrt => {
let op = op.to_scalar().to_u32()?;
// FIXME using host floats
let sqrt = Single::from_bits(f32::from_bits(op).sqrt().to_bits().into());
let rsqrt = (Single::from_u128(1).value / sqrt).value;
// Apply a relative error with a magnitude on the order of 2^-12 to simulate the
// inaccuracy of RSQRT.
let res = apply_random_float_error(this, rsqrt, -12);
Ok(Scalar::from_f32(res))
}
}
}
/// Disturbes a floating-point result by a relative error on the order of (-2^scale, 2^scale).
#[allow(clippy::arithmetic_side_effects)] // floating point arithmetic cannot panic
fn apply_random_float_error<F: rustc_apfloat::Float>(
this: &mut crate::MiriInterpCx<'_, '_>,
val: F,
err_scale: i32,
) -> F {
let rng = this.machine.rng.get_mut();
// generates rand(0, 2^64) * 2^(scale - 64) = rand(0, 1) * 2^scale
let err =
F::from_u128(rng.gen::<u64>().into()).value.scalbn(err_scale.checked_sub(64).unwrap());
// give it a random sign
let err = if rng.gen::<bool>() { -err } else { err };
// multiple the value with (1+err)
(val * (F::from_u128(1).value + err).value).value
}
/// Performs `which` operation on the first component of `op` and copies
/// the other components. The result is stored in `dest`.
fn unary_op_ss<'tcx>(
this: &mut crate::MiriInterpCx<'_, 'tcx>,
which: FloatUnaryOp,
op: &OpTy<'tcx, Provenance>,
dest: &PlaceTy<'tcx, Provenance>,
) -> InterpResult<'tcx, ()> {
let (op, op_len) = this.operand_to_simd(op)?;
let (dest, dest_len) = this.place_to_simd(dest)?;
assert_eq!(dest_len, op_len);
let res0 = unary_op_f32(this, which, &this.read_immediate(&this.project_index(&op, 0)?)?)?;
this.write_scalar(res0, &this.project_index(&dest, 0)?)?;
for i in 1..dest_len {
this.copy_op(
&this.project_index(&op, i)?,
&this.project_index(&dest, i)?,
/*allow_transmute*/ false,
)?;
}
Ok(())
}
/// Performs `which` operation on each component of `op`, storing the
/// result is stored in `dest`.
fn unary_op_ps<'tcx>(
this: &mut crate::MiriInterpCx<'_, 'tcx>,
which: FloatUnaryOp,
op: &OpTy<'tcx, Provenance>,
dest: &PlaceTy<'tcx, Provenance>,
) -> InterpResult<'tcx, ()> {
let (op, op_len) = this.operand_to_simd(op)?;
let (dest, dest_len) = this.place_to_simd(dest)?;
assert_eq!(dest_len, op_len);
for i in 0..dest_len {
let op = this.read_immediate(&this.project_index(&op, i)?)?;
let dest = this.project_index(&dest, i)?;
let res = unary_op_f32(this, which, &op)?;
this.write_scalar(res, &dest)?;
}
Ok(())
}