Thanks for the detailed review, and apologies for the extra churn caused by the incomplete change. Thank you also for reverting it on trunk.
I have posted v4 of the corrected patch as a new thread: [PATCH v4 4/4] MIPS: Add XBurst MXU target option https://sourceware.org/pipermail/gcc-patches/2026-July/724128.html The new version describes the XBurst MXU (Matrix Unit) extension and notes that GCC does not currently generate MXU instructions. It models the option after the MCU ASE by adding TARGET_MXU, defining __mips_mxu, and forwarding -mmxu and -mno-mxu through ASM_SPEC. It also documents the options, emits .module mxu from mips_file_start, and adds compiler, driver, and testsuite-harness coverage. Thanks again for pointing out the missing infrastructure. Eldar.
