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use rustc_middle::mir;
use rustc_middle::ty::layout::LayoutOf as _;
use rustc_middle::ty::Ty;
use rustc_span::Symbol;
use rustc_target::abi::Size;
use rustc_target::spec::abi::Abi;
use crate::*;
/// A bitmask constant for scrutinizing the immediate byte provided
/// to the string comparison intrinsics. It distinuishes between
/// 16-bit integers and 8-bit integers. See [`compare_strings`]
/// for more details about the immediate byte.
const USE_WORDS: u8 = 1;
/// A bitmask constant for scrutinizing the immediate byte provided
/// to the string comparison intrinsics. It distinuishes between
/// signed integers and unsigned integers. See [`compare_strings`]
/// for more details about the immediate byte.
const USE_SIGNED: u8 = 2;
/// The main worker for the string comparison intrinsics, where the given
/// strings are analyzed according to the given immediate byte.
///
/// # Arguments
///
/// * `str1` - The first string argument. It is always a length 16 array of bytes
/// or a length 8 array of two-byte words.
/// * `str2` - The second string argument. It is always a length 16 array of bytes
/// or a length 8 array of two-byte words.
/// * `len` is the length values of the supplied strings. It is distinct from the operand length
/// in that it describes how much of `str1` and `str2` will be used for the calculation and may
/// be smaller than the array length of `str1` and `str2`. The string length is counted in bytes
/// if using byte operands and in two-byte words when using two-byte word operands.
/// If the value is `None`, the length of a string is determined by the first
/// null value inside the string.
/// * `imm` is the immediate byte argument supplied to the intrinsic. The byte influences
/// the operation as follows:
///
/// ```text
/// 0babccddef
/// || | |||- Use of bytes vs use of two-byte words inside the operation.
/// || | ||
/// || | ||- Use of signed values versus use of unsigned values.
/// || | |
/// || | |- The comparison operation performed. A total of four operations are available.
/// || | * Equal any: Checks which characters of `str2` are inside `str1`.
/// || | * String ranges: Check if characters in `str2` are inside the provided character ranges.
/// || | Adjacent characters in `str1` constitute one range.
/// || | * String comparison: Mark positions where `str1` and `str2` have the same character.
/// || | * Substring search: Mark positions where `str1` is a substring in `str2`.
/// || |
/// || |- Result Polarity. The result bits may be subjected to a bitwise complement
/// || if these bits are set.
/// ||
/// ||- Output selection. This bit has two meanings depending on the instruction.
/// | If the instruction is generating a mask, it distinguishes between a bit mask
/// | and a byte mask. Otherwise it distinguishes between the most significand bit
/// | and the least significand bit when generating an index.
/// |
/// |- This bit is ignored. It is expected that this bit is set to zero, but it is
/// not a requirement.
/// ```
///
/// # Returns
///
/// A result mask. The bit at index `i` inside the mask is set if 'str2' starting at `i`
/// fulfills the test as defined inside the immediate byte.
/// The mask may be negated if negation flags inside the immediate byte are set.
///
/// For more information, see the Intel Software Developer's Manual, Vol. 2b, Chapter 4.1.
#[allow(clippy::arithmetic_side_effects)]
fn compare_strings<'tcx>(
this: &mut MiriInterpCx<'tcx>,
str1: &OpTy<'tcx>,
str2: &OpTy<'tcx>,
len: Option<(u64, u64)>,
imm: u8,
) -> InterpResult<'tcx, i32> {
let default_len = default_len::<u64>(imm);
let (len1, len2) = if let Some(t) = len {
t
} else {
let len1 = implicit_len(this, str1, imm)?.unwrap_or(default_len);
let len2 = implicit_len(this, str2, imm)?.unwrap_or(default_len);
(len1, len2)
};
let mut result = 0;
match (imm >> 2) & 3 {
0 => {
// Equal any: Checks which characters of `str2` are inside `str1`.
for i in 0..len2 {
let ch2 = this.read_immediate(&this.project_index(str2, i)?)?;
for j in 0..len1 {
let ch1 = this.read_immediate(&this.project_index(str1, j)?)?;
let eq = this.binary_op(mir::BinOp::Eq, &ch1, &ch2)?;
if eq.to_scalar().to_bool()? {
result |= 1 << i;
break;
}
}
}
}
1 => {
// String ranges: Check if characters in `str2` are inside the provided character ranges.
// Adjacent characters in `str1` constitute one range.
let len1 = len1 - (len1 & 1);
let get_ch = |ch: Scalar| -> InterpResult<'tcx, i32> {
let result = match (imm & USE_WORDS != 0, imm & USE_SIGNED != 0) {
(true, true) => i32::from(ch.to_i16()?),
(true, false) => i32::from(ch.to_u16()?),
(false, true) => i32::from(ch.to_i8()?),
(false, false) => i32::from(ch.to_u8()?),
};
Ok(result)
};
for i in 0..len2 {
for j in (0..len1).step_by(2) {
let ch2 = get_ch(this.read_scalar(&this.project_index(str2, i)?)?)?;
let ch1_1 = get_ch(this.read_scalar(&this.project_index(str1, j)?)?)?;
let ch1_2 = get_ch(this.read_scalar(&this.project_index(str1, j + 1)?)?)?;
if ch1_1 <= ch2 && ch2 <= ch1_2 {
result |= 1 << i;
}
}
}
}
2 => {
// String comparison: Mark positions where `str1` and `str2` have the same character.
result = (1 << default_len) - 1;
result ^= (1 << len1.max(len2)) - 1;
for i in 0..len1.min(len2) {
let ch1 = this.read_immediate(&this.project_index(str1, i)?)?;
let ch2 = this.read_immediate(&this.project_index(str2, i)?)?;
let eq = this.binary_op(mir::BinOp::Eq, &ch1, &ch2)?;
result |= i32::from(eq.to_scalar().to_bool()?) << i;
}
}
3 => {
// Substring search: Mark positions where `str1` is a substring in `str2`.
if len1 == 0 {
result = (1 << default_len) - 1;
} else if len1 <= len2 {
for i in 0..len2 {
if len1 > len2 - i {
break;
}
result |= 1 << i;
for j in 0..len1 {
let k = i + j;
if k >= default_len {
break;
} else {
let ch1 = this.read_immediate(&this.project_index(str1, j)?)?;
let ch2 = this.read_immediate(&this.project_index(str2, k)?)?;
let ne = this.binary_op(mir::BinOp::Ne, &ch1, &ch2)?;
if ne.to_scalar().to_bool()? {
result &= !(1 << i);
break;
}
}
}
}
}
}
_ => unreachable!(),
}
// Polarity: Possibly perform a bitwise complement on the result.
match (imm >> 4) & 3 {
3 => result ^= (1 << len1) - 1,
1 => result ^= (1 << default_len) - 1,
_ => (),
}
Ok(result)
}
/// Obtain the arguments of the intrinsic based on its name.
/// The result is a tuple with the following values:
/// * The first string argument.
/// * The second string argument.
/// * The string length values, if the intrinsic requires them.
/// * The immediate instruction byte.
///
/// The string arguments will be transmuted into arrays of bytes
/// or two-byte words, depending on the value of the immediate byte.
/// Originally, they are [__m128i](https://doc.rust-lang.org/stable/core/arch/x86_64/struct.__m128i.html) values
/// corresponding to the x86 128-bit integer SIMD type.
fn deconstruct_args<'tcx>(
unprefixed_name: &str,
this: &mut MiriInterpCx<'tcx>,
link_name: Symbol,
abi: Abi,
args: &[OpTy<'tcx>],
) -> InterpResult<'tcx, (OpTy<'tcx>, OpTy<'tcx>, Option<(u64, u64)>, u8)> {
let array_layout_fn = |this: &mut MiriInterpCx<'tcx>, imm: u8| {
if imm & USE_WORDS != 0 {
this.layout_of(Ty::new_array(this.tcx.tcx, this.tcx.types.u16, 8))
} else {
this.layout_of(Ty::new_array(this.tcx.tcx, this.tcx.types.u8, 16))
}
};
// The fourth letter of each string comparison intrinsic is either 'e' for "explicit" or 'i' for "implicit".
// The distinction will correspond to the intrinsics type signature. In this constext, "explicit" and "implicit"
// refer to the way the string length is determined. The length is either passed explicitly in the "explicit"
// case or determined by a null terminator in the "implicit" case.
let is_explicit = match unprefixed_name.as_bytes().get(4) {
Some(&b'e') => true,
Some(&b'i') => false,
_ => unreachable!(),
};
if is_explicit {
let [str1, len1, str2, len2, imm] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let imm = this.read_scalar(imm)?.to_u8()?;
let default_len = default_len::<u32>(imm);
let len1 = u64::from(this.read_scalar(len1)?.to_u32()?.min(default_len));
let len2 = u64::from(this.read_scalar(len2)?.to_u32()?.min(default_len));
let array_layout = array_layout_fn(this, imm)?;
let str1 = str1.transmute(array_layout, this)?;
let str2 = str2.transmute(array_layout, this)?;
Ok((str1, str2, Some((len1, len2)), imm))
} else {
let [str1, str2, imm] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let imm = this.read_scalar(imm)?.to_u8()?;
let array_layout = array_layout_fn(this, imm)?;
let str1 = str1.transmute(array_layout, this)?;
let str2 = str2.transmute(array_layout, this)?;
Ok((str1, str2, None, imm))
}
}
/// Calculate the c-style string length for a given string `str`.
/// The string is either a length 16 array of bytes a length 8 array of two-byte words.
fn implicit_len<'tcx>(
this: &mut MiriInterpCx<'tcx>,
str: &OpTy<'tcx>,
imm: u8,
) -> InterpResult<'tcx, Option<u64>> {
let mut result = None;
let zero = ImmTy::from_int(0, str.layout.field(this, 0));
for i in 0..default_len::<u64>(imm) {
let ch = this.read_immediate(&this.project_index(str, i)?)?;
let is_zero = this.binary_op(mir::BinOp::Eq, &ch, &zero)?;
if is_zero.to_scalar().to_bool()? {
result = Some(i);
break;
}
}
Ok(result)
}
#[inline]
fn default_len<T: From<u8>>(imm: u8) -> T {
if imm & USE_WORDS != 0 { T::from(8u8) } else { T::from(16u8) }
}
impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
pub(super) trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
fn emulate_x86_sse42_intrinsic(
&mut self,
link_name: Symbol,
abi: Abi,
args: &[OpTy<'tcx>],
dest: &MPlaceTy<'tcx>,
) -> InterpResult<'tcx, EmulateItemResult> {
let this = self.eval_context_mut();
this.expect_target_feature_for_intrinsic(link_name, "sse4.2")?;
// Prefix should have already been checked.
let unprefixed_name = link_name.as_str().strip_prefix("llvm.x86.sse42.").unwrap();
match unprefixed_name {
// Used to implement the `_mm_cmpestrm` and the `_mm_cmpistrm` functions.
// These functions compare the input strings and return the resulting mask.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#ig_expand=1044,922
"pcmpistrm128" | "pcmpestrm128" => {
let (str1, str2, len, imm) =
deconstruct_args(unprefixed_name, this, link_name, abi, args)?;
let mask = compare_strings(this, &str1, &str2, len, imm)?;
// The sixth bit inside the immediate byte distiguishes
// between a bit mask or a byte mask when generating a mask.
if imm & 0b100_0000 != 0 {
let (array_layout, size) = if imm & USE_WORDS != 0 {
(this.layout_of(Ty::new_array(this.tcx.tcx, this.tcx.types.u16, 8))?, 2)
} else {
(this.layout_of(Ty::new_array(this.tcx.tcx, this.tcx.types.u8, 16))?, 1)
};
let size = Size::from_bytes(size);
let dest = dest.transmute(array_layout, this)?;
for i in 0..default_len::<u64>(imm) {
let result = helpers::bool_to_simd_element(mask & (1 << i) != 0, size);
this.write_scalar(result, &this.project_index(&dest, i)?)?;
}
} else {
let layout = this.layout_of(this.tcx.types.i128)?;
let dest = dest.transmute(layout, this)?;
this.write_scalar(Scalar::from_i128(i128::from(mask)), &dest)?;
}
}
// Used to implement the `_mm_cmpestra` and the `_mm_cmpistra` functions.
// These functions compare the input strings and return `1` if the end of the second
// input string is not reached and the resulting mask is zero, and `0` otherwise.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#ig_expand=919,1041
"pcmpistria128" | "pcmpestria128" => {
let (str1, str2, len, imm) =
deconstruct_args(unprefixed_name, this, link_name, abi, args)?;
let result = if compare_strings(this, &str1, &str2, len, imm)? != 0 {
false
} else if let Some((_, len)) = len {
len >= default_len::<u64>(imm)
} else {
implicit_len(this, &str1, imm)?.is_some()
};
this.write_scalar(Scalar::from_i32(i32::from(result)), dest)?;
}
// Used to implement the `_mm_cmpestri` and the `_mm_cmpistri` functions.
// These functions compare the input strings and return the bit index
// for most significant or least significant bit of the resulting mask.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#ig_expand=921,1043
"pcmpistri128" | "pcmpestri128" => {
let (str1, str2, len, imm) =
deconstruct_args(unprefixed_name, this, link_name, abi, args)?;
let mask = compare_strings(this, &str1, &str2, len, imm)?;
let len = default_len::<u32>(imm);
// The sixth bit inside the immediate byte distiguishes between the least
// significant bit and the most significant bit when generating an index.
let result = if imm & 0b100_0000 != 0 {
// most significant bit
31u32.wrapping_sub(mask.leading_zeros()).min(len)
} else {
// least significant bit
mask.trailing_zeros().min(len)
};
this.write_scalar(Scalar::from_i32(i32::try_from(result).unwrap()), dest)?;
}
// Used to implement the `_mm_cmpestro` and the `_mm_cmpistro` functions.
// These functions compare the input strings and return the lowest bit of the
// resulting mask.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#ig_expand=923,1045
"pcmpistrio128" | "pcmpestrio128" => {
let (str1, str2, len, imm) =
deconstruct_args(unprefixed_name, this, link_name, abi, args)?;
let mask = compare_strings(this, &str1, &str2, len, imm)?;
this.write_scalar(Scalar::from_i32(mask & 1), dest)?;
}
// Used to implement the `_mm_cmpestrc` and the `_mm_cmpistrc` functions.
// These functions compare the input strings and return `1` if the resulting
// mask was non-zero, and `0` otherwise.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#ig_expand=920,1042
"pcmpistric128" | "pcmpestric128" => {
let (str1, str2, len, imm) =
deconstruct_args(unprefixed_name, this, link_name, abi, args)?;
let mask = compare_strings(this, &str1, &str2, len, imm)?;
this.write_scalar(Scalar::from_i32(i32::from(mask != 0)), dest)?;
}
// Used to implement the `_mm_cmpistrz` and the `_mm_cmpistrs` functions.
// These functions return `1` if the string end has been reached and `0` otherwise.
// Since these functions define the string length implicitly, it is equal to a
// search for a null terminator (see `deconstruct_args` for more details).
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#ig_expand=924,925
"pcmpistriz128" | "pcmpistris128" => {
let [str1, str2, imm] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let imm = this.read_scalar(imm)?.to_u8()?;
let str = if unprefixed_name == "pcmpistris128" { str1 } else { str2 };
let array_layout = if imm & USE_WORDS != 0 {
this.layout_of(Ty::new_array(this.tcx.tcx, this.tcx.types.u16, 8))?
} else {
this.layout_of(Ty::new_array(this.tcx.tcx, this.tcx.types.u8, 16))?
};
let str = str.transmute(array_layout, this)?;
let result = implicit_len(this, &str, imm)?.is_some();
this.write_scalar(Scalar::from_i32(i32::from(result)), dest)?;
}
// Used to implement the `_mm_cmpestrz` and the `_mm_cmpestrs` functions.
// These functions return 1 if the explicitly passed string length is smaller
// than 16 for byte-sized operands or 8 for word-sized operands.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#ig_expand=1046,1047
"pcmpestriz128" | "pcmpestris128" => {
let [_, len1, _, len2, imm] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let len = if unprefixed_name == "pcmpestris128" { len1 } else { len2 };
let len = this.read_scalar(len)?.to_i32()?;
let imm = this.read_scalar(imm)?.to_u8()?;
this.write_scalar(
Scalar::from_i32(i32::from(len < default_len::<i32>(imm))),
dest,
)?;
}
// Used to implement the `_mm_crc32_u{8, 16, 32, 64}` functions.
// These functions calculate a 32-bit CRC using `0x11EDC6F41`
// as the polynomial, also known as CRC32C.
// https://datatracker.ietf.org/doc/html/rfc3720#section-12.1
"crc32.32.8" | "crc32.32.16" | "crc32.32.32" | "crc32.64.64" => {
let bit_size = match unprefixed_name {
"crc32.32.8" => 8,
"crc32.32.16" => 16,
"crc32.32.32" => 32,
"crc32.64.64" => 64,
_ => unreachable!(),
};
if bit_size == 64 && this.tcx.sess.target.arch != "x86_64" {
return Ok(EmulateItemResult::NotSupported);
}
let [left, right] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let left = this.read_scalar(left)?;
let right = this.read_scalar(right)?;
let crc = if bit_size == 64 {
// The 64-bit version will only consider the lower 32 bits,
// while the upper 32 bits get discarded.
#[allow(clippy::cast_possible_truncation)]
u128::from((left.to_u64()? as u32).reverse_bits())
} else {
u128::from(left.to_u32()?.reverse_bits())
};
let v = match bit_size {
8 => u128::from(right.to_u8()?.reverse_bits()),
16 => u128::from(right.to_u16()?.reverse_bits()),
32 => u128::from(right.to_u32()?.reverse_bits()),
64 => u128::from(right.to_u64()?.reverse_bits()),
_ => unreachable!(),
};
// Perform polynomial division modulo 2.
// The algorithm for the division is an adapted version of the
// schoolbook division algorithm used for normal integer or polynomial
// division. In this context, the quotient is not calculated, since
// only the remainder is needed.
//
// The algorithm works as follows:
// 1. Pull down digits until division can be performed. In the context of division
// modulo 2 it means locating the most significant digit of the dividend and shifting
// the divisor such that the position of the divisors most significand digit and the
// dividends most significand digit match.
// 2. Perform a division and determine the remainder. Since it is arithmetic modulo 2,
// this operation is a simple bitwise exclusive or.
// 3. Repeat steps 1. and 2. until the full remainder is calculated. This is the case
// once the degree of the remainder polynomial is smaller than the degree of the
// divisor polynomial. In other words, the number of leading zeros of the remainder
// is larger than the number of leading zeros of the divisor. It is important to
// note that standard arithmetic comparison is not applicable here:
// 0b10011 / 0b11111 = 0b01100 is a valid division, even though the dividend is
// smaller than the divisor.
let mut dividend = (crc << bit_size) ^ (v << 32);
const POLYNOMIAL: u128 = 0x11EDC6F41;
while dividend.leading_zeros() <= POLYNOMIAL.leading_zeros() {
dividend ^=
(POLYNOMIAL << POLYNOMIAL.leading_zeros()) >> dividend.leading_zeros();
}
let result = u32::try_from(dividend).unwrap().reverse_bits();
let result = if bit_size == 64 {
Scalar::from_u64(u64::from(result))
} else {
Scalar::from_u32(result)
};
this.write_scalar(result, dest)?;
}
_ => return Ok(EmulateItemResult::NotSupported),
}
Ok(EmulateItemResult::NeedsReturn)
}
}