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Loader: Support HI16/16 pairs, not just LO16 #17602

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merged 2 commits into from
Jun 19, 2023

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unknownbrackets
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@unknownbrackets unknownbrackets commented Jun 19, 2023

#17561 tripped in Motorstorm: Arctic Edge, but initially making sure pairs matched didn't make any obvious impact.

https://report.ppsspp.org/logs/kind/1185

After some testing and comparing with PSP relocation behavior (mostly via RAM dumps), it seems that R_MIPS_16 (and maybe any other type) is paired with the R_MIPS_HI16 relocation for the purposes of the carry.

After matching that behavior, the shadows in the game appear to be fixed. Fixes #7552.

-[Unknown]

Motorstorm: Arctic Edge US uses these pairs for some VFPU loads.
Without relocating these, strange shadows show underneath vehicles.

It appears as if actual firmware pairs with any non-HI16 relocation.
@unknownbrackets unknownbrackets added this to the v1.16.0 milestone Jun 19, 2023
@hrydgard
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Oh wow, talk about a non-obvious cause of a graphical issue! Great find!

Could you link to the report on report.ppsspp.org in this PR description?

@kotcrab
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kotcrab commented Sep 16, 2024

Looking at loadcore behavior it indeed uses the first non HI16 relocation after finding HI16. I implemented this now in ghidra-allegrex.

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MotorStorm Arctic Edge USA - Abnormal Shadow
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