The old logic would always emit LEA when both sources are in a register
and OE is disabled. However, ADD is still preferable when one of the
sources matches the destination.
Before:
45 8D 6C 35 00 lea r13d,[r13+rsi]
After:
44 03 EE add r13d,esi
Identical, except that this used a temporary register as scratch instead
of RCX. round_long_acc now no longer needs scratch, so we can
deduplicate the logic.
Prior to this commit, the emitter would emit a 7-byte instruction when
loading a 32-bit immediate to a 64-bit register.
0: 48 c7 c0 ff ff ff 7f mov rax,0x7fffffff
With this change, it will check if it can instead emit a load to a
32-bit register, which takes only 5 or 6 bytes.
0: b8 ff ff ff 7f mov eax,0x7fffffff
Prior to this commit, the emitter would unconditionally emit a 10-byte
instruction known as MOVABS when loading a 64-bit immediate to a
register.
0: 48 b8 ef be ad de 00 movabs rax,0xdeadbeef
7: 00 00 00
With this change, it will instead rely on the fact that on x64 writes to
32-bit registers are automatically zero extended to 64-bits, allowing
us to emit a 5 or 6-bytes instruction with the same effect for certain
immediates.
0: b8 ef be ad de mov eax,0xdeadbeef
Prior to this commit, the emitter would unconditionally emit a 10-byte
instruction known as MOVABS when loading a 64-bit immediate to a
register.
0: 48 b8 ef be ad de ff movabs rax,0xffffffffdeadbeef
7: ff ff ff
With this change, it will instead emit a 7-byte instruction when it is
possible to express the 64-bit immediate using a signed 32-bit value.
0: 48 c7 c0 ef be ad de mov rax,0xffffffffdeadbeef
Sintendo