Replace the bool parameter force5bytes in J, JMP, and J_CC with an enum
class Jump::Short/Near. Many callers set that parameter to the literal
'true', which was unclear if you didn't already know what it did.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
Due to the way the ModRM encoding works on x86, memory addressing
combinations involving RBP or R13 need an additional byte for an 8-bit
displacement of zero.
However, this was also applied in cases where it is unnecessary,
effectively wasting a byte.
- MatR with RSP or R12
8B 44 24 00 mov eax,dword ptr [rsp]
8B 04 24 mov eax,dword ptr [rsp]
- MRegSum with base != RBP or R13
46 8D 7C 37 00 lea r15d,[rdi+r14]
46 8D 3C 37 lea r15d,[rdi+r14]
- MComplex without offset
8B 4C CA 00 mov ecx,dword ptr [rdx+rcx*8]
8B 0C CA mov ecx,dword ptr [rdx+rcx*8]
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
* The high half of regOp is immediately overwritten so the value in it is irrelevant.
* MOVSD produces an unnecessary dependency on the high half of regOp.
* MOVAPS is implemented as a register rename on modern microarchitectures.
There is no reason to use MOVAPD over MOVAPS, for two reasons:
* There has never been a microarchitecture with separate single and double domains.
* MOVAPD is one byte longer than MOVAPS
