Jit64: addx revisited #9464
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Jit64: addx revisited #9464
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FYI, all of the examples are labeled "1" |
Oops, thanks for pointing that out. |
lioncash
reviewed
Jan 26, 2021
This doesn't really add any new optimizations, but fixes an issue that prevented the optimizations introduced in dolphin-emu#8551 and dolphin-emu#8755 from being applied in specific cases. A similar issue was solved for subfx as part of dolphin-emu#9425. Consider the case where the destination register is also an input register and happens to hold an immediate value. This results in a set of constraints that forces the RegCache to allocate a register and move the immediate value into it for us. By the time we check for immediate values in the JIT, we're too late. We solve this by refactoring the code in such a way that we can check for immediates before involving the RegCache. - Example 1 Before: 41 BF 00 68 00 CC mov r15d,0CC006800h 44 03 FF add r15d,edi After: 44 8D BF 00 68 00 CC lea r15d,[rdi-33FF9800h] - Example 2 Before: 41 BE 00 00 00 00 mov r14d,0 44 03 F7 add r14d,edi After: 44 8B F7 mov r14d,edi - Example 3 Before: 41 BD 03 00 00 00 mov r13d,3 44 03 6D 8C add r13d,dword ptr [rbp-74h] After: 44 8B 6D 8C mov r13d,dword ptr [rbp-74h] 41 83 C5 03 add r13d,3
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Is there any more comments/complaints to this? |
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Can I test on my Redmi Note 9 android phone? |
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This change affects the x64 JIT, not the ARM JIT. Most android devices use ARM, so I don't think this would have any meaningful impact there. |
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Poking this pr |
Tilka
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Jun 28, 2021
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This doesn't really add any new optimizations, but fixes an issue that prevented the optimizations introduced in #8551 and #8755 from being applied in specific cases. A similar issue was solved for subfx as part of #9425.
Consider the case where the destination register is also an input register and happens to hold an immediate value. This results in a set of constraints that forces the RegCache to allocate a register and move the immediate value into it for us. By the time we check for immediate values in the JIT, we're too late.
We solve this by refactoring the code in such a way that we can check for immediates before involving the RegCache.
Example 1
Before:
After:
Example 2
Before:
After:
Example 3
Before:
After: