feat: Reject conflicting RISC-V ISA extensions#1526
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davidlattimore
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Feb 11, 2026
lapla-cogito
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Feb 11, 2026
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| /// Conflicting pairs of RISC-V ISA extensions. | ||
| const RISCV_CONFLICTING_EXT_PAIRS: &[(&str, &str)] = &[ | ||
| ("f", "zfinx"), | ||
| ("d", "zdinx"), | ||
| ("q", "zqinx"), | ||
| ("zfh", "zhinx"), | ||
| ("zfhmin", "zhinxmin"), | ||
| ]; |
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For record-keeping, let me explain why I'm listing these pairs: Zfinx specifies the following:
Every current and future extension that uses
Fregisters will also have anZFinxversion that is incompatible with the extension.
According to this, enabling any of these pairs simultaneously in the same implementation would violate the intent of the specification.
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Additionally, this list is somewhat excessive. If we were strictly limited to rv64gc, the minimum necessary would be just (f, zfinx) and (d, zdinx). However, rather than properly updating this list in the future, I considered it more meaningful to proactively exclude other pairs here.
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part of #916
While base ISA conflicts are already caught by
merge_eflags, there were no checks to detect conflicting combinations of ISA extensions.