[Mips] Add -mips-split-hi16 for PS2 IOP modules #4

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techwritescode merged 1 commit from ps2-iop-split-hi into r5900-ee 2026-10-12 04:45:33 +00:00

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techwritescode commented 2026-10-12 04:27:58 +00:00

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PS2 IOP modules built with LLVM were rejected by the boot ROM (error -201, ELF type 0xFF81). Cause: one lui shared by several accesses leaves more R_MIPS_LO16 than R_MIPS_HI16 relocations, which IRX1 cannot represent, so the fixup tool falls back to IRX2.

-mllvm -mips-split-hi16 (hidden, off by default):

• MipsSplitHi16 (pre-RA): clone the %hi lui in front of every user. The clones carry an implicit $zero use so MachineLateInstrsCleanup does not merge them again.
• MipsSinkHi16 (pre-emit): move each lui down to the instruction that reads it.
• MipsELFObjectWriter::sortRelocs: pair each HI16 with the first following unclaimed LO16 of the same symbol and place it directly before it.

Tests: CodeGen/Mips/split-hi16.ll, split-hi16-reloc.ll. Verified end to end: usbd, bdm, bdmfs_fatfs, usbmass_bd, iomanx, filexio built with this load in PCSX2, and the std::filesystem example passes with 0 failures using them.

🤖 Generated with Claude Code

PS2 IOP modules built with LLVM were rejected by the boot ROM (error -201, ELF type 0xFF81). Cause: one lui shared by several accesses leaves more R_MIPS_LO16 than R_MIPS_HI16 relocations, which IRX1 cannot represent, so the fixup tool falls back to IRX2. `-mllvm -mips-split-hi16` (hidden, off by default): - MipsSplitHi16 (pre-RA): clone the %hi lui in front of every user. The clones carry an implicit $zero use so MachineLateInstrsCleanup does not merge them again. - MipsSinkHi16 (pre-emit): move each lui down to the instruction that reads it. - MipsELFObjectWriter::sortRelocs: pair each HI16 with the first following unclaimed LO16 of the same symbol and place it directly before it. Tests: CodeGen/Mips/split-hi16.ll, split-hi16-reloc.ll. Verified end to end: usbd, bdm, bdmfs_fatfs, usbmass_bd, iomanx, filexio built with this load in PCSX2, and the std::filesystem example passes with 0 failures using them. 🤖 Generated with [Claude Code](https://claude.com/claude-code)

techwritescode added 1 commit 2026-10-12 04:27:58 +00:00

[Mips] Add -mips-split-hi16: one lui per %hi use, HI16 right before its LO16 ... 619102f222

The PS2 IOP module format (IRX1) pairs each R_MIPS_HI16 with the single
R_MIPS_LO16 that follows it. Instruction selection shares one lui between
every access to the same symbol, and the ELF writer groups all HI16
relocations ahead of the LO16 ones, so such code cannot be turned into an
IRX1 module.

With the option, a pre-RA pass gives every user of a %hi lui its own copy,
a pre-emit pass moves each lui down to its user, and the ELF writer puts each
HI16 directly before its LO16.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

techwritescode referenced this pull request from ps2/sdk-core 2026-10-12 04:28:10 +00:00

irx.h: make IRX import/export tables work when built with clang #15

techwritescode referenced this pull request from ps2/llvm-toolchain 2026-10-12 04:28:26 +00:00

iop-clang: pass -mips-split-hi16 #7

techwritescode referenced this pull request from ps2/ps2build 2026-10-12 04:28:28 +00:00

llvm: build IOP modules as IRX1 #12

techwritescode merged commit 619102f222 into r5900-ee 2026-10-12 04:45:33 +00:00

techwritescode deleted branch ps2-iop-split-hi 2026-10-12 04:45:34 +00:00

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