user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Move out addition logic

Browse source
This commit is contained in:
Tobias Decking 2024-06-21 17:55:22 +02:00
parent 9afd752591
commit ed83f1acce
1 changed files with 29 additions and 39 deletions
Download patch file Download diff file Expand all files Collapse all files

68
src/tools/miri/src/shims/x86/mod.rs
View file

@ -45,25 +45,17 @@ pub(super) trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
return Ok(EmulateItemResult::NotSupported);
}
let [cb_in, a, b] = this.check_shim(abi, Abi::Unadjusted, link_name, args)?;
let op = if unprefixed_name.starts_with("add") {
mir::BinOp::AddWithOverflow
} else {
mir::BinOp::SubWithOverflow
};
let [cb_in, a, b] = this.check_shim(abi, Abi::Unadjusted, link_name, args)?;
let cb_in = this.read_scalar(cb_in)?.to_u8()? != 0;
let a = this.read_immediate(a)?;
let b = this.read_immediate(b)?;
let (sum, overflow1) = this.binary_op(op, &a, &b)?.to_pair(this);
let (sum, overflow2) =
this.binary_op(op, &sum, &ImmTy::from_uint(cb_in, a.layout))?.to_pair(this);
let cb_out = overflow1.to_scalar().to_bool()? | overflow2.to_scalar().to_bool()?;
let d1 = this.project_field(dest, 0)?;
let d2 = this.project_field(dest, 1)?;
write_twice(this, &d1, Scalar::from_u8(cb_out.into()), &d2, sum)?;
let (sum, cb_out) = carrying_add(this, cb_in, a, b, op)?;
this.write_scalar(cb_out, &this.project_field(dest, 0)?)?;
this.write_immediate(*sum, &this.project_field(dest, 1)?)?;
}
// Used to implement the `_addcarryx_u{32, 64}` functions. They are semantically identical with the `_addcarry_u{32, 64}` functions,
@ -77,23 +69,10 @@ pub(super) trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
}
let [c_in, a, b, out] = this.check_shim(abi, Abi::Unadjusted, link_name, args)?;
let c_in = this.read_scalar(c_in)?.to_u8()? != 0;
let a = this.read_immediate(a)?;
let b = this.read_immediate(b)?;
let (sum, overflow1) =
this.binary_op(mir::BinOp::AddWithOverflow, &a, &b)?.to_pair(this);
let (sum, overflow2) = this
.binary_op(
mir::BinOp::AddWithOverflow,
&sum,
&ImmTy::from_uint(c_in, a.layout),
)?
.to_pair(this);
let c_out = overflow1.to_scalar().to_bool()? | overflow2.to_scalar().to_bool()?;
let out = this.deref_pointer_as(out, sum.layout)?;
write_twice(this, dest, Scalar::from_u8(c_out.into()), &out, sum)?;
let (sum, c_out) = carrying_add(this, c_in, a, b, mir::BinOp::AddWithOverflow)?;
this.write_scalar(c_out, dest)?;
this.write_immediate(*sum, &this.deref_pointer_as(out, sum.layout)?)?;
}
// Used to implement the `_mm_pause` function.
@ -1369,15 +1348,26 @@ fn psign<'tcx>(
Ok(())
}
/// Write two values `v1` and `v2` to the places `d1` and `d2`.
fn write_twice<'tcx>(
/// Calcultates either `a + b + cb_in` or `a - b - cb_in` depending on the value
/// of `op` and returns both the sum and the overflow bit. `op` is expected to be
/// either one of `mir::BinOp::AddWithOverflow` and `mir::BinOp::SubWithOverflow`.
fn carrying_add<'tcx>(
this: &mut crate::MiriInterpCx<'tcx>,
d1: &MPlaceTy<'tcx>,
v1: Scalar,
d2: &MPlaceTy<'tcx>,
v2: ImmTy<'tcx>,
) -> InterpResult<'tcx, ()> {
this.write_scalar(v1, d1)?;
this.write_immediate(*v2, d2)?;
Ok(())
cb_in: &OpTy<'tcx>,
a: &OpTy<'tcx>,
b: &OpTy<'tcx>,
op: mir::BinOp,
) -> InterpResult<'tcx, (ImmTy<'tcx>, Scalar)> {
assert!(op == mir::BinOp::AddWithOverflow || op == mir::BinOp::SubWithOverflow);
let cb_in = this.read_scalar(cb_in)?.to_u8()? != 0;
let a = this.read_immediate(a)?;
let b = this.read_immediate(b)?;
let (sum, overflow1) = this.binary_op(op, &a, &b)?.to_pair(this);
let (sum, overflow2) =
this.binary_op(op, &sum, &ImmTy::from_uint(cb_in, a.layout))?.to_pair(this);
let cb_out = overflow1.to_scalar().to_bool()? | overflow2.to_scalar().to_bool()?;
Ok((sum, Scalar::from_u8(cb_out.into())))
}