STATUS_ILLEGAL_INSTRUCTION in emulated x86-64 mod DLL (Monster Hunter Rise + REFramework, ARM64EC)

Title
STATUS_ILLEGAL_INSTRUCTION in emulated x86-64 mod DLL (Monster Hunter Rise + REFramework, ARM64EC)

I'm not a developer, I collected the logs and the addresses below on request from the docs, but I cannot interpret them. Happy to run whatever further commands would help.

Hardware
AYN Odin 3 Ultra
Device tree reports ayn,odin3 / qcom,cq8725s / qcom,sm8750-mtp / qcom,sm8750
(Qualcomm Dragonwing Q8, Oryon CPU, Adreno 830)

CPU features from /proc/cpuinfo
fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm
jscvt fcma lrcpc dcpop sha3 sm3 sm4 asimddp sha512 asimdfhm dit uscat ilrcpc
flagm ssbs sb paca pacg dcpodp flagm2 frint i8mm bf16 rng bti ecv afp rpres
No sve, no sve2, no sme, no mops.

OS
Armada Linux, bootc image mode, kernel 7.2.0-rc7 aarch64
gamescope session, Vulkan instance 1.4.341

Software
Monster Hunter Rise
Proton 11.0 (ARM64), build proton-11.0-2-rc7, steamrt4 4.0.20260805.254769
libarm64ecfex.dll loaded as the ARM64EC emulation module
REFramework v1.5.9.1, commit ec6c81fd39831b328027ae00e102bc9c9c3f8aa5, build 28.07.2026
Only dinput8.dll installed. reframework/plugins and reframework/autorun both empty.

The same thing happens every time game starts. The REFramework menu appears on screen and reports that it is initializing. Shortly after, it crashes. Should be noted the game plays flawlessly vanilla, and that this is probably an issue with all REEngine games which support REFramework, not just MHRise.

[mhrise.tar.gz](https://github.com/user-attachments/files/31268572/mhrise.tar.gz)

From the log

Initializing REFramework SDK...
RETypes initialization
Exception occurred: c000001d
RIP: 6ffff80f2660
Module: 6ffff80c0000 C:\windows\system32\dinput8.dll

This happens on every ARM Proton build I try.

Start by reproducing the crash with the listed ARM64 Proton build, Monster Hunter Rise, and REFramework, then inspect mhrise.tar.gz and the log entry for exception c000001d at RIP 6ffff80f2660 in dinput8.dll. Done means identifying the source of the unsupported instruction and establishing whether the issue is specific to REFramework or affects other REEngine games.

Written by the indexing model from the issue text.