Jit64: Clean up ExtractWithByteOffset #12672
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RCOpArg::ExtractWithByteOffset is only used in one place: a special case of rlwinmx. ExtractWithByteOffset first stores the value of the specified register into m_ppc_state (unless it's already there), and then returns an offset into m_ppc_state. Our use of this function has two undesirable properties (except in the trivial case `offset == 0`): 1. ExtractWithByteOffset calls StoreFromRegister without going through any of the usual functions. This violated an assumption I made when working on my constant propagation PR and led to a hard-to-find bug. 2. If the specified register is in a host register and is dirty, ExtractWithByteOffset will store its value to m_ppc_state even when it's unnecessary. In particular, this always happens when rlwinmx uses the same register as input and output, since rlwinmx always allocates a host register for the output and marks it as dirty. Since ExtractWithByteOffset is only used in one place, I figure we might as well inline it there. This commit does that, and also alters rlwinmx's logic so the special case code is only triggered when the input is already in m_ppc_state. Input in `m_ppc_state`, before (11 bytes): mov esi, dword ptr [rbp-104] mov dword ptr [rbp-104], esi movzx esi, byte ptr [rbp-101] Input in `m_ppc_state`, after (5 bytes): movzx esi, byte ptr [rbp-101] Input in host register, before (8 bytes): mov dword ptr [rbp-104], esi movzx esi, byte ptr [rbp-101] Input in host register, after (3 bytes): shr edi, 0x18
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Shortly tested it and didn't immediately hit a bug. |
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RCOpArg::ExtractWithByteOffsetis only used in one place: a special case ofrlwinmx.ExtractWithByteOffsetfirst stores the value of the specified register intom_ppc_state(unless it's already there), and then returns an offset intom_ppc_state. Our use of this function has two undesirable properties (except in the trivial caseoffset == 0):ExtractWithByteOffsetcallsStoreFromRegisterwithout going through any of the usual functions. This violated an assumption I made when working on my constant propagation PR and led to a hard-to-find bug.ExtractWithByteOffsetwill store its value tom_ppc_stateeven when it's unnecessary. In particular, this always happens whenrlwinmxuses the same register as input and output, sincerlwinmxalways allocates a host register for the output and marks it as dirty.Since
ExtractWithByteOffsetis only used in one place, I figure we might as well inline it there. This commit does that, and also altersrlwinmx's logic so the special case code is only triggered when the input is already inm_ppc_state.Input in
m_ppc_state, before (11 bytes):Input in
m_ppc_state, after (5 bytes):Input in host register, before (8 bytes):
Input in host register, after (3 bytes):