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rexcode/arm32: document BF family as intentionally unimplemented

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The 5 Branch Future mnemonics (BF/BFI_BR/BFL/BFLX/BFCSEL) are left
enum-only on purpose: deprecated ARMv8.1-M, not disassemblable by
llvm-objdump (so unverifiable), and a correct encoder needs dual-offset
PC-relative relocation infrastructure that doesn't exist. Noted in the
enum for future readers.
This commit is contained in:
Brendan Punsky
2026-06-18 03:05:25 -04:00
committed by Flāvius
parent a63fb51fdd
commit e4cff78a70
1 changed files with 9 additions and 2 deletions
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11
core/rexcode/arm32/mnemonics.odin
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@@ -405,8 +405,15 @@ Mnemonic :: enum u16 {
LETP, // loop end with tail predication
LCTP, // loop clear tail predication
BF, // branch future (ARMv8.1-M)
BFI_BR, // branch future indirect
// Branch Future (ARMv8.1-M). INTENTIONALLY NOT ENCODED: this feature is
// deprecated and effectively dead -- llvm-objdump cannot even disassemble
// these, so they can't be round-trip-verified, and a correct encoder would
// need dual-offset PC-relative relocation infrastructure (a `boff` bf-point
// plus a separate branch target, both linker fixups) that does not exist
// here. Left as enum-only on purpose; revisit only if BF is ever needed,
// by first adding BRANCH_BF_* relocation types + a resolver.
BF, // branch future
BFI_BR, // branch future indirect (bfx)
BFL, // branch future and link
BFLX, // branch future link and exchange
BFCSEL, // branch future conditional select