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use rustc_span::Symbol;
use rustc_target::spec::abi::Abi;
use crate::*;
impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
pub(super) trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
fn emulate_x86_bmi_intrinsic(
&mut self,
link_name: Symbol,
abi: Abi,
args: &[OpTy<'tcx>],
dest: &MPlaceTy<'tcx>,
) -> InterpResult<'tcx, EmulateItemResult> {
let this = self.eval_context_mut();
// Prefix should have already been checked.
let unprefixed_name = link_name.as_str().strip_prefix("llvm.x86.bmi.").unwrap();
// The intrinsics are suffixed with the bit size of their operands.
let (is_64_bit, unprefixed_name) = if unprefixed_name.ends_with("64") {
(true, unprefixed_name.strip_suffix(".64").unwrap_or(""))
} else {
(false, unprefixed_name.strip_suffix(".32").unwrap_or(""))
};
// All intrinsics of the "bmi" namespace belong to the "bmi2" ISA extension.
// The exception is "bextr", which belongs to "bmi1".
let target_feature = if unprefixed_name == "bextr" { "bmi1" } else { "bmi2" };
this.expect_target_feature_for_intrinsic(link_name, target_feature)?;
if is_64_bit && 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 left = if is_64_bit { left.to_u64()? } else { u64::from(left.to_u32()?) };
let right = if is_64_bit { right.to_u64()? } else { u64::from(right.to_u32()?) };
let result = match unprefixed_name {
// Extract a contigous range of bits from an unsigned integer.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_bextr_u32
"bextr" => {
let start = u32::try_from(right & 0xff).unwrap();
let len = u32::try_from((right >> 8) & 0xff).unwrap();
let shifted = left.checked_shr(start).unwrap_or(0);
// Keep the `len` lowest bits of `shifted`, or all bits if `len` is too big.
if len >= 64 { shifted } else { shifted & 1u64.wrapping_shl(len).wrapping_sub(1) }
}
// Create a copy of an unsigned integer with bits above a certain index cleared.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_bzhi_u32
"bzhi" => {
let index = u32::try_from(right & 0xff).unwrap();
// Keep the `index` lowest bits of `left`, or all bits if `index` is too big.
if index >= 64 { left } else { left & 1u64.wrapping_shl(index).wrapping_sub(1) }
}
// Extract bit values of an unsigned integer at positions marked by a mask.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_pext_u32
"pext" => {
let mut mask = right;
let mut i = 0u32;
let mut result = 0;
// Iterate over the mask one 1-bit at a time, from
// the least significant bit to the most significant bit.
while mask != 0 {
// Extract the bit marked by the mask's least significant set bit
// and put it at position `i` of the result.
result |= u64::from(left & (1 << mask.trailing_zeros()) != 0) << i;
i = i.wrapping_add(1);
// Clear the least significant set bit.
mask &= mask.wrapping_sub(1);
}
result
}
// Deposit bit values of an unsigned integer to positions marked by a mask.
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_pdep_u32
"pdep" => {
let mut mask = right;
let mut set = left;
let mut result = 0;
// Iterate over the mask one 1-bit at a time, from
// the least significant bit to the most significant bit.
while mask != 0 {
// Put rightmost bit of `set` at the position of the current `mask` bit.
result |= (set & 1) << mask.trailing_zeros();
// Go to next bit of `set`.
set >>= 1;
// Clear the least significant set bit.
mask &= mask.wrapping_sub(1);
}
result
}
_ => return Ok(EmulateItemResult::NotSupported),
};
let result = if is_64_bit {
Scalar::from_u64(result)
} else {
Scalar::from_u32(u32::try_from(result).unwrap())
};
this.write_scalar(result, dest)?;
Ok(EmulateItemResult::NeedsReturn)
}
}