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LibJIT: Generate MOV ModR/M without displacement when possible

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For non-extended register bases and 0x0 offset, we can emit a ModR/M
byte without displacement.
This commit is contained in:
Andreas Kling 2023-10-28 19:23:14 +02:00
parent 4cc24548f6
commit 32d3a47058
1 changed files with 6 additions and 2 deletions
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8
Userland/Libraries/LibJIT/Assembler.h
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@ -161,7 +161,9 @@ struct Assembler {
| ((to_underlying(src.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x89);
if (dst.offset_or_immediate <= 127) {
if (dst.reg <= Reg::RDI && dst.offset_or_immediate == 0) {
emit8(0x00 | (encode_reg(src.reg) << 3) | encode_reg(dst.reg));
} else if (dst.offset_or_immediate <= 127) {
emit8(0x40 | (encode_reg(src.reg) << 3) | encode_reg(dst.reg));
emit8(dst.offset_or_immediate);
} else {
@ -176,7 +178,9 @@ struct Assembler {
| ((to_underlying(dst.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(src.reg) >= 8) ? 1 << 0 : 0));
emit8(0x8b);
if (src.offset_or_immediate <= 127) {
if (src.reg <= Reg::RDI && src.offset_or_immediate == 0) {
emit8(0x00 | (encode_reg(dst.reg) << 3) | encode_reg(src.reg));
} else if (src.offset_or_immediate <= 127) {
emit8(0x40 | (encode_reg(dst.reg) << 3) | encode_reg(src.reg));
emit8(src.offset_or_immediate);
} else {