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cranelift x64: use the TZCNT instruction for Ctz when it's available;

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This commit is contained in:
Benjamin Bouvier
2021-01-28 12:02:47 +01:00
parent d3acd9a283
commit 6bf6612d96
4 changed files with 53 additions and 4 deletions
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3
cranelift/codegen/src/isa/x64/inst/args.rs
View File

@@ -404,6 +404,8 @@ pub enum UnaryRmROpcode {
Bsf,
/// Counts leading zeroes (Leading Zero CouNT).
Lzcnt,
/// Counts trailing zeroes (Trailing Zero CouNT).
Tzcnt,
}
impl fmt::Debug for UnaryRmROpcode {
@@ -412,6 +414,7 @@ impl fmt::Debug for UnaryRmROpcode {
UnaryRmROpcode::Bsr => write!(fmt, "bsr"),
UnaryRmROpcode::Bsf => write!(fmt, "bsf"),
UnaryRmROpcode::Lzcnt => write!(fmt, "lzcnt"),
UnaryRmROpcode::Tzcnt => write!(fmt, "tzcnt"),
}
}
}

5
cranelift/codegen/src/isa/x64/inst/emit.rs
View File

@@ -680,11 +680,11 @@ pub(crate) fn emit(
let prefix = match size {
2 => match op {
UnaryRmROpcode::Bsr | UnaryRmROpcode::Bsf => LegacyPrefixes::_66,
UnaryRmROpcode::Lzcnt => LegacyPrefixes::_66F3,
UnaryRmROpcode::Lzcnt | UnaryRmROpcode::Tzcnt => LegacyPrefixes::_66F3,
},
4 | 8 => match op {
UnaryRmROpcode::Bsr | UnaryRmROpcode::Bsf => LegacyPrefixes::None,
UnaryRmROpcode::Lzcnt => LegacyPrefixes::_F3,
UnaryRmROpcode::Lzcnt | UnaryRmROpcode::Tzcnt => LegacyPrefixes::_F3,
},
_ => unreachable!(),
};
@@ -693,6 +693,7 @@ pub(crate) fn emit(
UnaryRmROpcode::Bsr => (0x0fbd, 2),
UnaryRmROpcode::Bsf => (0x0fbc, 2),
UnaryRmROpcode::Lzcnt => (0x0fbd, 2),
UnaryRmROpcode::Tzcnt => (0x0fbc, 2),
};
match src {