They were plain i64 constants handed to op_imm, so any integer typed as
one and `inst_mrs(X0, 999999)` compiled fine. Worse, the printer could
not tell a system register from an immediate and had to recover the
distinction by mnemonic and slot -- MSR's other form holds a PSTATE
field selector in the same position, so it keyed off whether operand 1
was a register.
System_Register is now its own type with its own Operand_Kind, union
member and op_sysreg constructor, exactly as Cond is. The printer's slot
logic is gone: the operand knows what it is, so naming it is a case in
the same switch that prints every other operand kind. MSR's PSTATE
selector is typed PSTATE_FIELD, which is what it always was.
It cannot join `Register` itself: that is a u16 with the class in its
high byte, leaving 8 bits for the number, and a system register needs
15. Widening it would break `Memory`, which packs two registers plus a
displacement and a mode into exactly 64 bits.
The constants are also reorganised. They had accreted into overlapping
sections -- two "ID registers" groups, three cache groups, a "Batch 5:
comprehensive sysreg sweep" banner, and a "hmm let me recompute" note
left in a comment. All 231 are now grouped by architectural function
(18 groups, alphabetical within each) with their five fields aligned.
Verified unchanged against llvm-mc: 222 registers byte-exact through
MRS, 8 write-only through MSR, and the PSTATE form still decodes as an
immediate rather than a register.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018UmHLRF11EoWwNWCJ7JGaA
These are what an assembler writes -- and what one prints back -- for
CSINC/CSINV/CSNEG with the condition inverted, and none of the five
existed. A disassembly of `cset w0, eq` came out as
`csinc w0, wzr, wzr, ne`.
Two constraints the table could not state before:
- The condition is stored inverted, so COND_HI_INV packs `cond ~ 1`
and reads it back the same way. The printer needs nothing; the
decoder hands it a plain condition operand.
- cinc/cinv/cneg are only the alias when Rn == Rm, which is a
cross-field equality no mask expresses. One operand fills both
slots on the way in (RN_RM), and decode checks the two fields agree
before accepting the entry -- reached only on a mask match, so it
costs nothing in the scan.
The aliases also require cond != 111x. That one *is* expressible: the
14 legal values are covered exactly by three masked patterns (0xxx,
10xx, 110x), so AL and NV fall through to the underlying instruction
the way llvm-mc does. COND_NOT_AL rejects them on the encode side.
Verified against llvm-mc across all five mnemonics, both widths and all
14 conditions: 140/140 of our printed strings assemble to exactly our
bytes. Disassembly agrees except for cs/hs and cc/lo, which is the
package's existing spelling of those two conditions and shows up on
CSEL and B.cond alike. AL/NV and Rn != Rm both fall through correctly.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018UmHLRF11EoWwNWCJ7JGaA
Encoder
* LSR/ASR by immediate used the generic IMM12 encoding, which writes bits
10-21 -- straight into the imms field the UBFM/SBFM base pattern already
fills, so immr stayed 0 and every shift encoded as #0 (`asr x0,x1,#7`
gave 9340fc20, not 9347fc20). They need immr alone, since imms is the
constant 31/63 fixed in the form: new ENC_SHIFT_IMMR.
* LDP/STP and friends borrowed the single-register addressing encodings,
which put an UNSCALED 9-bit displacement at bits 20:12 and OR a pre/post
marker into bits 11:10. The pair forms want a SCALED 7-bit value at
21:15, and bits 11:10 are part of Rt2 -- so `ldp x0,x1,[x2,#16]!` came
back with Rt2=3. New OFFSET_PAIR_4/8/16 (the scale does not follow from
the register type: LDPSW pairs X registers but loads words, STGP scales
by 16), with the addressing mode read from bits[24:23] where the
architecture keeps it. 26 forms retargeted.
Decoder
* Vector operands came back with size=4 always, so a decoded V register
lost its arrangement and disassembly printed a bare `v0` that no
assembler would take. Reconstruct it from the form's operand type.
* Vd/Vn/Vm/Va hardcoded REG_V, but SVE forms use those same slots with
Z_REG_* operands -- `add z0.d, z0.d, z0.d` decoded as a V register.
Take the class from the operand type, as every other slot already does.
Printer
* V/Z registers now print their arrangement (`add v0.4s, v1.4s, v2.4s`,
`add z0.d, ...`). Element views (op_v_elem_*) moved from 1/2/4/8 to odd
codes 1/3/5/7, because an element-D view and an 8B arrangement were both
size 8 and could not be told apart.
* MOVZ/MOVN/MOVK print the hw index as `lsl #16`, omitted when zero.
* BC_COND folds its condition into the mnemonic like B_COND already did,
instead of printing it twice.
Table (each bit pattern re-derived from llvm-mc)
* BTI_J and BTI_C had each other's encodings.
* FCMLA's mask left size bit 22 free, so .4s and .2d were indistinguishable
and .2d decoded as .4s.
* BFDOT carried the Q=0 pattern for its .4s/.8h form; PMULLB/PMULLT were
missing the size field; TLBI PAALL/PAALLOS had the wrong CRm/op2.
* RDSVL's imm6 sits at bits 10:5, not where IMM6 puts it: ENC_IMM6_LO.
Nine test expectations that asserted the wrong values were corrected.
specgen.lua
Was already dead before the mnemonic work -- it wrote to encoding_table.odin
and spliced a SPECGEN region, neither of which survived the merge into
instruction_table.odin. Retargeted, taught the canonical names, and made it
emit Form literals (Encoding + Clobber). It can no longer own whole
`.MNEM = { ... }` blocks either, since ADD now holds integer, NEON and SVE
forms together, so it MERGES: a form is added only when no (bits, mask)
match exists, and existing rows are never rewritten -- their hand-maintained
Clobber data has to survive a regeneration.
Verified: all 11 rexcode suites match HEAD exactly (arm64 461/461); the three
generator stages stay idempotent; a 73-case differential against llvm-mc is
byte-exact for both encode and decode round-trip. Over the whole decode table,
canonical-form disassembly re-assembled by llvm-mc goes from 594 byte-exact /
1818 unassemblable to 1737 / 678. Re-running specgen re-derives 1130 forms
from llvm-mc and finds every one already present, which independently confirms
those bit patterns.
Still open: multi-vector register lists ({z0.b, z1.b}) and lane indices
(v0.s[2]) are not modelled, so those forms print without them.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Roll the encode/decode buffer-sizing helpers (added for x86 in 49787b7de) out
to every other ISA, and document them in the cross-arch naming contract.
Per arch (arm32, arm64, mips, riscv, ppc, ppc_vle, rsp, mos6502, mos65816):
- encode_max_code_size / encode_max_relocation_count now key off the
[]Instruction slice (were int counts); bodies unchanged (* MAX_INST_SIZE).
- encode_reserve(code, relocs, instructions): grows the caller's code []u8 by
length and reserves relocs by capacity; allocates no new buffers.
- decode_max_instruction_count / decode_estimate_instruction_count: exact
ceiling and typical estimate, keyed off the min/avg instruction size per
arch (fixed-4: arm64/mips/ppc/rsp; min-2: arm32/riscv/ppc_vle; min-1: mos).
- decode_reserve(instructions, inst_info, label_defs, data, exact=false).
docs/cross_arch_design.md: helpers added to the naming contract.
No behavior change to the existing size helpers (signature only). All 10 ISAs
check + test green (x86 2282, arm32 600, arm64 461, mips 281, riscv 154, ppc 31,
ppc_vle 281, rsp 70, mos6502 148, mos65816 53).
Move all ten ISA packages (x86, arm32, arm64, mips, riscv, ppc, ppc_vle,
rsp, mos6502, mos65816) from core/rexcode/<arch> to core/rexcode/isa/<arch>,
so the import pattern is now `import "core:rexcode/isa/x86"`. The shared
core stays at core:rexcode/isa.
Mechanical: relative `import "../isa"` / "../../isa" -> absolute
"core:rexcode/isa" (the only path that survives the move; the "../" and
"../.." self/generated imports move with their packages). build.lua now
builds paths as <root>/isa/<name>; stale `cd <arch>` hints in the verify
tools and the doc.odin paths updated.
WASM stays at core/rexcode/wasm for now -- it is an IR, not an ISA, and
will move under the forthcoming core:rexcode/ir once that layer lands.
All 10 arches gen/builders/check/test green; import core:rexcode/isa/x86
verified working; wasm still compiles.
