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
B_COND was a straight contradiction of the rule the rest of the enum follows.
No assembler has a mnemonic called `b.cond`; it has `b.eq`, `b.le`, `b.ne` and
thirteen more, and x86 in this same library already models exactly this shape
the right way -- JE, JNE, JG, JLE are sixteen separate mnemonics with the
condition in the opcode.
Two things were wrong with folding it into an operand.
The condition is not an operand. It is four bits of the opcode, no different
from x86 putting Jcc's condition in the low nibble of 0x7_. Modelling it as
one has to be papered over everywhere: the printer special-cased B_COND to
rebuild `b.eq` out of operand 0, sbprint had to skip that operand so it did
not print twice, and the public mnemonic_to_string -- which has no instruction
to read the operand from -- returned "b_cond", a string no assembler takes.
All three of those are now gone; the name prints itself.
More importantly it destroyed the flag data. x86 records per condition which
status bits it consults: JE reads {ZF}, JLE reads {ZF, SF, OF}. One B_COND
entry could not say that, so it claimed nzcv_rd = {N, Z, C, V} -- all four
flags, for every condition. Every entry was wrong. Split apart they carry what
they actually read:
b.eq/b.ne Z b.hi/b.ls Z, C
b.cs/b.cc C b.ge/b.lt N, V
b.mi/b.pl N b.gt/b.le N, Z, V
b.vs/b.vc V b.al/b.nv none
which is the data the compiler's asm checker reads for flag liveness, now that
arm64 feeds it.
The mask also covers the condition field for the first time (0xFF000010 ->
0xFF00001F): with the condition in an operand, four opcode bits sat outside
the mask.
BC.cond gets the same treatment. Builders come out per condition, so `b.le` is
`inst_b_le(label)` rather than `inst_b_cond(.LE, label)`. Cond stays exactly as
it is -- CSEL, CSINC, CSINV, CSNEG, CCMP, CCMN and FCSEL take a real condition
operand, and the compiler's OP_COND handling is untouched.
All sixteen verified by disassembling our own output with llvm-mc: b.eq, b.ne,
b.hs, b.lo, b.mi, b.pl, b.vs, b.vc, b.hi, b.ls, b.ge, b.lt, b.gt, b.le, b.al,
b.nv. Rows follow the table's current column formatting. All rexcode suites
pass and the generators stay idempotent.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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>
The Mnemonic enum had one member per encoding form -- ADD_IMM, ADD_SR,
ADD_ER, ADD_V for what an assembler just calls ADD; LDR, LDR_LIT, LDR_PRE,
LDR_POST, LDR_REG, LDR_V for LDR; SVE_ADD_Z / SVE_ADD_PRED / SVE_AND_P for
names SVE spells ADD and AND. The encoder never needed that: like x86, it
already resolves a mnemonic by scanning its run of forms and matching
operand types, so the split bought nothing and cost a printer that had to
strip suffixes back off at runtime -- incompletely, so ADD_V printed
"add.v", LDR_PRE "ldr.pre" and FCVT_H_S "fcvt.h.s".
Collapse the enum to the names assemblers accept: 1104 -> 785 mnemonics,
with the variants becoming forms under one name (ADD now has 13, LDR 15).
LSLV/LSRV/ASRV/RORV fold into LSL/LSR/ASR/ROR. Form order within a run is
precedence, and the original declaration order is already the order an
assembler resolves: "add w0,w1,w2" takes the shifted-register form, and
only the extended form can encode SP.
This needed one structural change. The matcher was blind to addressing
mode -- `case .MEM: return op.kind == .MEMORY` -- which is precisely why
LDR/LDR_PRE/LDR_POST/LDR_REG had to be separate mnemonics; all 20 merge
collisions were this and nothing else. Split Operand_Type.MEM into
mode-specific types (MEM_OFFSET/PRE/POST/REG/EXT plus four SVE), matching
how W_REG/W_SHIFTED/W_EXTENDED are already distinct types over one
register class. The decoder derives Address_Mode from `enc`, so it is
unaffected.
Encodings are unchanged: the multiset of (ops, enc, bits, mask, feature,
flags) over all forms is identical before and after except for two entries
deliberately dropped. NOT_V_ALIAS duplicated NOT_V byte for byte, and
MOV_V_ALIAS was wrong -- it encoded VN where the ORR-based MOV alias needs
VN_VM_DUP, so "mov v1.8b, v2.8b" would have emitted "orr v1.8b, v2.8b,
v0.8b".
AMX_* keeps its prefix: Apple's coprocessor is undocumented with no
assembler spelling, so there is no canonical name to collapse to and bare
"set"/"clr"/"ldx" would mislead. The two-token system instructions keep
theirs too and print with a space (dc zva, tlbi vae1, bti j).
Verified: all 11 rexcode suites match HEAD exactly (arm64 461/461); the
three generator stages round-trip idempotently; 754 of 785 mnemonics are
accepted by llvm-mc, the rest being AMX (24), TME (4, no +tme in this LLVM
build), B_COND/BC_COND and TBL2; and a 39-case encode/print differential
against llvm-mc matches 34, with the 5 others confirmed byte-identical at
HEAD (pre-existing LSR/ASR immediate and LDP pre-index packing bugs, and
printer gaps for vector arrangements and MOVZ/MOVK shifts).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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.
