Skip to content

YJIT: expand bitwise shift support in x86 assembler #8174

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
maximecb merged 1 commit into from
Aug 4, 2023
Merged

YJIT: expand bitwise shift support in x86 assembler #8174

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 25 additions & 15 deletions yjit/src/asm/x86_64/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1223,8 +1223,8 @@ pub fn ret(cb: &mut CodeBlock) {
cb.write_byte(0xC3);
}

// Encode a single-operand shift instruction
fn write_shift(cb: &mut CodeBlock, op_mem_one_pref: u8, _op_mem_cl_pref: u8, op_mem_imm_pref: u8, op_ext: Option<u8>, opnd0: X86Opnd, opnd1: X86Opnd) {
// Encode a bitwise shift instruction
fn write_shift(cb: &mut CodeBlock, op_mem_one_pref: u8, op_mem_cl_pref: u8, op_mem_imm_pref: u8, op_ext: u8, opnd0: X86Opnd, opnd1: X86Opnd) {
assert!(matches!(opnd0, X86Opnd::Reg(_) | X86Opnd::Mem(_)));

// Check the size of opnd0
Expand All @@ -1234,16 +1234,26 @@ fn write_shift(cb: &mut CodeBlock, op_mem_one_pref: u8, _op_mem_cl_pref: u8, op_
let sz_pref = opnd_size == 16;
let rex_w = opnd_size == 64;

if let X86Opnd::UImm(imm) = opnd1 {
if imm.value == 1 {
write_rm(cb, sz_pref, rex_w, X86Opnd::None, opnd0, op_ext, &[op_mem_one_pref]);
} else {
assert!(imm.num_bits <= 8);
write_rm(cb, sz_pref, rex_w, X86Opnd::None, opnd0, op_ext, &[op_mem_imm_pref]);
cb.write_byte(imm.value as u8);
match opnd1 {
X86Opnd::UImm(imm) => {
if imm.value == 1 {
write_rm(cb, sz_pref, rex_w, X86Opnd::None, opnd0, Some(op_ext), &[op_mem_one_pref]);
} else {
assert!(imm.num_bits <= 8);
write_rm(cb, sz_pref, rex_w, X86Opnd::None, opnd0, Some(op_ext), &[op_mem_imm_pref]);
cb.write_byte(imm.value as u8);
}
}

X86Opnd::Reg(reg) => {
// We can only use CL/RCX as the shift amount
assert!(reg.reg_no == RCX_REG.reg_no);
write_rm(cb, sz_pref, rex_w, X86Opnd::None, opnd0, Some(op_ext), &[op_mem_cl_pref]);
}

_ => {
unreachable!();
}
} else {
unreachable!();
}
}

Expand All @@ -1254,7 +1264,7 @@ pub fn sal(cb: &mut CodeBlock, opnd0: X86Opnd, opnd1: X86Opnd) {
0xD1, // opMemOnePref,
0xD3, // opMemClPref,
0xC1, // opMemImmPref,
Some(0x04),
0x04,
opnd0,
opnd1
);
Expand All @@ -1267,7 +1277,7 @@ pub fn sar(cb: &mut CodeBlock, opnd0: X86Opnd, opnd1: X86Opnd) {
0xD1, // opMemOnePref,
0xD3, // opMemClPref,
0xC1, // opMemImmPref,
Some(0x07),
0x07,
opnd0,
opnd1
);
Expand All @@ -1280,7 +1290,7 @@ pub fn shl(cb: &mut CodeBlock, opnd0: X86Opnd, opnd1: X86Opnd) {
0xD1, // opMemOnePref,
0xD3, // opMemClPref,
0xC1, // opMemImmPref,
Some(0x04),
0x04,
opnd0,
opnd1
);
Expand All @@ -1293,7 +1303,7 @@ pub fn shr(cb: &mut CodeBlock, opnd0: X86Opnd, opnd1: X86Opnd) {
0xD1, // opMemOnePref,
0xD3, // opMemClPref,
0xC1, // opMemImmPref,
Some(0x05),
0x05,
opnd0,
opnd1
);
Expand Down
1 change: 1 addition & 0 deletions yjit/src/asm/x86_64/tests.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -340,6 +340,7 @@ fn test_sal() {
check_bytes("d1e1", |cb| sal(cb, ECX, uimm_opnd(1)));
check_bytes("c1e505", |cb| sal(cb, EBP, uimm_opnd(5)));
check_bytes("d1642444", |cb| sal(cb, mem_opnd(32, RSP, 68), uimm_opnd(1)));
check_bytes("48d3e1", |cb| sal(cb, RCX, CL));
}

#[test]
Expand Down