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configure mul to use 'bigger' src registers when needed

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Folkert 2022-08-21 20:26:26 +02:00
parent aacd90baff
commit 6b69e837a4
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2 changed files with 28 additions and 10 deletions
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28
crates/compiler/gen_dev/src/generic64/x86_64.rs
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@ -1332,12 +1332,25 @@ impl X86_64Assembler {
}
}
const REX: u8 = 0x40;
const REX_W: u8 = REX | 0x8;
// see https://wiki.osdev.org/X86-64_Instruction_Encoding#Encoding
/// If set, 64-bit operand size is used
const REX_PREFIX_W: u8 = 0b1000;
/// Extension to the MODRM.reg
const REX_PREFIX_R: u8 = 0b0100;
#[allow(unused)]
/// Extension to the SIB.index field
const REX_PREFIX_X: u8 = 0b0010;
/// Extension to the MODRM.rm
const REX_PREFIX_B: u8 = 0b0001;
/// Wide REX
const REX_W: u8 = REX | REX_PREFIX_W;
#[inline(always)]
fn add_rm_extension<T: RegTrait>(reg: T, byte: u8) -> u8 {
if reg.value() > 7 {
byte | 1
byte | REX_PREFIX_B
} else {
byte
}
@ -1351,7 +1364,7 @@ fn add_opcode_extension(reg: X86_64GeneralReg, byte: u8) -> u8 {
#[inline(always)]
fn add_reg_extension<T: RegTrait>(reg: T, byte: u8) -> u8 {
if reg.value() > 7 {
byte | 4
byte | REX_PREFIX_R
} else {
byte
}
@ -1560,7 +1573,14 @@ fn imul_reg64_reg64(buf: &mut Vec<'_, u8>, dst: X86_64GeneralReg, src: X86_64Gen
/// `MUL r/m64` -> Unsigned Multiply r/m64 to r64.
#[inline(always)]
fn mul_reg64_reg64(buf: &mut Vec<'_, u8>, src: X86_64GeneralReg) {
binop_reg64_reg64(0xF7, buf, X86_64GeneralReg::RAX, src);
let mut rex = REX_W;
rex = add_reg_extension(src, rex);
if src.value() > 7 {
rex |= REX_PREFIX_B;
}
buf.extend(&[rex, 0xF7, 0b1110_0000 | (src as u8 % 8)]);
}
/// Jump near, relative, RIP = RIP + 32-bit displacement sign extended to 64-bits.