cli/q
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Improved x64 documentation

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This commit is contained in:
Eduard Urbach 2024-07-23 10:47:27 +02:00
parent eb160afd91
commit d6db1b1096
Signed by: akyoto
GPG Key ID: C874F672B1AF20C0
4 changed files with 24 additions and 18 deletions
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19
src/build/arch/x64/ModRM.go
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@ -1,16 +1,19 @@
package x64
// AddressMode encodes the addressing mode.
type AddressMode = byte
const (
AddressMemory = byte(0b00)
AddressMemoryOffset8 = byte(0b01)
AddressMemoryOffset32 = byte(0b10)
AddressDirect = byte(0b11)
AddressMemory = AddressMode(0b00)
AddressMemoryOffset8 = AddressMode(0b01)
AddressMemoryOffset32 = AddressMode(0b10)
AddressDirect = AddressMode(0b11)
)
// ModRM is used to generate a ModRM suffix.
// - mod: 2 bits
// - reg: 3 bits
// - rm: 3 bits
func ModRM(mod byte, reg byte, rm byte) byte {
// - mod: 2 bits. The addressing mode.
// - reg: 3 bits. Register reference or opcode extension.
// - rm: 3 bits. Register operand.
func ModRM(mod AddressMode, reg byte, rm byte) byte {
return (mod << 6) | (reg << 3) | rm
}

19
src/build/arch/x64/SIB.go
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@ -1,16 +1,19 @@
package x64
// ScaleFactor encodes the scale factor.
type ScaleFactor = byte
const (
Scale1 = byte(0b00)
Scale2 = byte(0b01)
Scale4 = byte(0b10)
Scale8 = byte(0b11)
Scale1 = ScaleFactor(0b00)
Scale2 = ScaleFactor(0b01)
Scale4 = ScaleFactor(0b10)
Scale8 = ScaleFactor(0b11)
)
// SIB is used to generate an SIB byte.
// - scale: 2 bits
// - index: 3 bits
// - base: 3 bits
func SIB(scale byte, index byte, base byte) byte {
// - scale: 2 bits. Multiplies the value of the index.
// - index: 3 bits. Specifies the index register.
// - base: 3 bits. Specifies the base register.
func SIB(scale ScaleFactor, index byte, base byte) byte {
return (scale << 6) | (index << 3) | base
}

2
src/build/arch/x64/encode.go
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@ -3,7 +3,7 @@ package x64
import "git.akyoto.dev/cli/q/src/build/cpu"
// encode is the core function that encodes an instruction.
func encode(code []byte, mod byte, reg cpu.Register, rm cpu.Register, numBytes byte, opCodes ...byte) []byte {
func encode(code []byte, mod AddressMode, reg cpu.Register, rm cpu.Register, numBytes byte, opCodes ...byte) []byte {
w := byte(0) // Indicates a 64-bit register.
r := byte(0) // Extension to the "reg" field in ModRM.
x := byte(0) // Extension to the SIB index field.

2
src/build/arch/x64/encodeNum.go
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@ -7,7 +7,7 @@ import (
)
// encodeNum encodes an instruction with up to two registers and a number parameter.
func encodeNum(code []byte, mod byte, reg cpu.Register, rm cpu.Register, number int, opCode8 byte, opCode32 byte) []byte {
func encodeNum(code []byte, mod AddressMode, reg cpu.Register, rm cpu.Register, number int, opCode8 byte, opCode32 byte) []byte {
if SizeOf(int64(number)) == 1 {
code = encode(code, mod, reg, rm, 8, opCode8)
return append(code, byte(number))