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A64/x64: Create a global_offset optimization for the page table.

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Instead of looking up the page table like:
  table[addr >> 12][addr & 0xFFF]
We can use a global offset on the table to query the memory like:
  table[addr >> 12][addr]

This saves two instructions on *every* memory access within the recompiler.

Thanks at skmp for the idea.
This commit is contained in:
Markus Wick 2019-12-31 00:08:35 +01:00 • committed by MerryMage
parent 7be0038186
commit 93668c24be
2 changed files with 10 additions and 0 deletions
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3
src/backend/x64/a64_emit_x64.cpp
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@ -737,6 +737,9 @@ static Xbyak::RegExp EmitVAddrLookup(BlockOfCode& code, A64EmitContext& ctx, Xby
code.mov(page_table, qword[page_table + tmp * sizeof(void*)]);
code.test(page_table, page_table);
code.jz(abort, code.T_NEAR);
if (ctx.conf.absolute_offset_page_table) {
return page_table + vaddr;
}
code.mov(tmp, vaddr);
code.and_(tmp, static_cast<u32>(page_size - 1));
return page_table + tmp;