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PowerPC: Raise alignment exceptions in more situations #9865

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PowerPC: Raise alignment exceptions in more situations #9865

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@JosJuice JosJuice commented Jul 5, 2021 •
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Intends to improve https://bugs.dolphin-emu.org/issues/12565.

To avoid affecting the performance, the JITs will most of the time not raise alignment exceptions unless you enable the new INI-only setting AlignmentExceptions.

JosJuice
JosJuice commented Jul 5, 2021
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Source/Core/Core/PowerPC/Jit64Common/Jit64AsmCommon.cpp
@@ -340,6 +340,9 @@ alignas(16) static const float m_m128 = -128.0f;
// Sizes of the various quantized store types
constexpr std::array<u8, 8> sizes{{32, 0, 0, 0, 8, 16, 8, 16}};

// TODO: Use the actual instruction being emulated (needed for alignment exception emulation)
static const UGeckoInstruction ps_placeholder_instruction = 0;
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Could someone who knows Jit64 better give me some advice here? Basically, I want to pass an additional argument to the quantized loadstore routines (so that the slowmem handler then can forward the argument when calling Read_* or Write_*), but all of RSCRATCH, RSCRATCH2 and RSCRATCH_EXTRA are already used for arguments to the quantized loadstore routines. How should I pass the argument?

@JosJuice JosJuice force-pushed the alignment-exceptions branch 3 times, most recently from ec3dcf7 to 82fbdd2 Compare July 5, 2021 10:21
@JosJuice JosJuice marked this pull request as draft July 5, 2021 13:06
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@JosJuice JosJuice force-pushed the alignment-exceptions branch 5 times, most recently from 009a9d5 to bc62fca Compare August 16, 2021 17:54
@JosJuice JosJuice marked this pull request as ready for review August 16, 2021 18:01
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While alignment exceptions turned out to have nothing to do with issue 12565, alignment exceptions are still something that would make sense for us to emulate (even if it doesn't affect any games). I've cleaned up the PR after the merge of the PR that fixed 12565, and it should be more or less done other than my earlier question about Jit64.

@JosJuice JosJuice force-pushed the alignment-exceptions branch 2 times, most recently from be099c2 to bc08553 Compare August 16, 2021 19:45
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@JosJuice JosJuice force-pushed the alignment-exceptions branch 2 times, most recently from 4ee50ff to 966dd51 Compare November 13, 2023 18:29
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@JosJuice
PowerPC: Don't overwrite argument in ReadFromHardware/WriteToHardware
a6f87cb 
Cleanup, and preparation for one of the upcoming commits.
@JosJuice
PowerPC: Use broader mask for checking loadstore exceptions
606d64a 
We will need to check for EXCEPTION_ALIGNMENT in addition to
EXCEPTION_DSI. Let's also throw in EXCEPTION_FAKE_MEMCHECK_HIT
while we're at it so we can skip doing fake DSI exceptions for that.

Reordering the exceptions enum is done for the sake of saving one
instruction on AArch64 when checking for loadstore exceptions.
(Bitwise operations can encode immediates containing a run of ones
of an arbitrary length, rotated by an arbitrary amount of bits.
In order to make use of this, all loadstore exceptions should
have adjacent bit positions.)
@JosJuice
PowerPC: Pass current instruction to Read/Write functions
6434def
@JosJuice
Add AlignmentExceptions setting
e0ba9e4
@JosJuice
PowerPC: Raise alignment exceptions in more situations
04ae7b7 
To avoid affecting performance, the JITs will most of the time not raise
alignment exceptions unless you enable the new INI-only setting
AlignmentExceptions.
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