diff options
Diffstat (limited to 'yjit/src/asm/arm64/inst/branch.rs')
-rw-r--r-- | yjit/src/asm/arm64/inst/branch.rs | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/yjit/src/asm/arm64/inst/branch.rs b/yjit/src/asm/arm64/inst/branch.rs new file mode 100644 index 0000000000..7f93f5e201 --- /dev/null +++ b/yjit/src/asm/arm64/inst/branch.rs @@ -0,0 +1,85 @@ +/// Which operation to perform. +enum Op { + /// Perform a BR instruction. + Br = 0b00, + + /// Perform a RET instruction. + Ret = 0b10 +} + +/// The struct that represents an A64 branch instruction that can be encoded. +/// +/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+ +/// | 31 30 29 28 | 27 26 25 24 | 23 22 21 20 | 19 18 17 16 | 15 14 13 12 | 11 10 09 08 | 07 06 05 04 | 03 02 01 00 | +/// | 1 1 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 | +/// | op... rn.............. rm.............. | +/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+ +/// +pub struct Branch { + /// The register holding the address to be branched to. + rn: u8, + + /// The operation to perform. + op: Op +} + +impl Branch { + /// BR + /// https://developer.arm.com/documentation/ddi0602/2022-03/Base-Instructions/BR--Branch-to-Register-?lang=en + pub fn br(rn: u8) -> Self { + Self { rn, op: Op::Br } + } + + /// RET + /// https://developer.arm.com/documentation/ddi0596/2021-12/Base-Instructions/RET--Return-from-subroutine-?lang=en + pub fn ret(rn: u8) -> Self { + Self { rn, op: Op::Ret } + } +} + +/// https://developer.arm.com/documentation/ddi0602/2022-03/Index-by-Encoding/Branches--Exception-Generating-and-System-instructions?lang=en +const FAMILY: u32 = 0b101; + +impl From<Branch> for u32 { + /// Convert an instruction into a 32-bit value. + fn from(inst: Branch) -> Self { + 0 + | (0b11 << 30) + | (FAMILY << 26) + | (1 << 25) + | ((inst.op as u32) << 21) + | (0b11111 << 16) + | ((inst.rn as u32) << 5) + } +} + +impl From<Branch> for [u8; 4] { + /// Convert an instruction into a 4 byte array. + fn from(inst: Branch) -> [u8; 4] { + let result: u32 = inst.into(); + result.to_le_bytes() + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn test_br() { + let result: u32 = Branch::br(0).into(); + assert_eq!(0xd61f0000, result); + } + + #[test] + fn test_ret() { + let result: u32 = Branch::ret(30).into(); + assert_eq!(0xd65f03C0, result); + } + + #[test] + fn test_ret_rn() { + let result: u32 = Branch::ret(20).into(); + assert_eq!(0xd65f0280, result); + } +} |