MOV_V (ORR alias: source feeds both Vn and Vm via a new VN_VM_DUP
encoding), MVN_V (NOT alias, plain 2-register), DUP_V (element form
Vd.T,Vn.Ts[i] and general form Vd.T,Wn/Xn), INS (element-to-element and
from-GPR), EXT_V (imm4 byte index). Adds a VEC_INDEX operand type plus
NEON_IDX5/NEON_IDX4/NEON_EXT_IDX encodings: the element-size marker rides
in the entry bits, the lane index drives the bits above it, and the
decoder recovers the element size from imm5's marker.
Element size now rides in op.size (B=1/H=2/S=4/D=8) via op_v_elem_b/h/s/d
so the matcher can disambiguate DUP/INS element forms; the builder
generator maps V_ELEM_* to those constructors. specgen derives the mask
by varying registers and each index field to its max -- the GPR-source
forms vary Vd and Rn independently (Rn 31 = wzr/xzr) so the low bit of
each field toggles. All 19 representative forms byte-exact vs llvm-mc and
decode-clean; 461 tests green. (TBL/TBX register-list forms deferred.)
SHRN/2, RSHRN/2, SQSHRN/2, UQSHRN/2, SQRSHRN/2, UQRSHRN/2, SQSHRUN/2,
SQRSHRUN/2 (16 forms). Verified against llvm-mc that immh keys on the
NARROW destination element (not the wide source), so the existing
NEON_SHR_IMM encoder/decoder (esize from ops[0]) is already correct --
this is a specgen-only change: right-shift esize now uses ESIZE[dst]
(equal to ESIZE[src] for same-arrangement shifts) plus narrowing
{narrow-dst, wide-src} arrangement tuples. All forms byte-exact and
decode-roundtrip verified across B/H/S element sizes; 461 tests green.
ZIP1/2, UZP1/2, TRN1/2 (three-same permute); CMLE/CMLT and FP
FCMLE/FCMLT (compare against zero, with the literal #0 / #0.0 operand);
SXTL/SXTL2/UXTL/UXTL2 (= SSHLL/USHLL #0, plain 2-register widen, shift
implicit in the static bits). All reuse the VD/VN/VM register slots, so
no encoder change. specgen gains an emit_cmp0 shape plus permute and
widen families. All forms byte-exact vs llvm-mc; 461 tests green.
Adds SSHLL/SSHLL2/USHLL/USHLL2 (12 forms) via specgen, reusing NEON_SHL_IMM (left shifts need no esize; the size marker is in bits). specgen's shift shape generalized to arrangement pairs {dst, src} with the shift element size taken from the source.
Verified: encode matches llvm-mc + decode recovers mnemonic + amount (sshll/sshll2/ushll across widths); arm64 check + 461 tests pass.
First encoder-extension family. Adds Operand_Type VEC_SHIFT and Operand_Encoding NEON_SHL_IMM/NEON_SHR_IMM: the element-size marker bit sits in the entry's bits, the encoder packs the amount into the low immh:immb bits (left = shift; right = esize - shift, esize from the vector operand via vec_esize/form.ops[0]), and the decoder recovers esize from immh to compute the amount.
Adds 13 mnemonics (91 forms) via specgen: left SHL/SLI/SQSHLU/SQSHL, right SSHR/USHR/SRSHR/URSHR/SSRA/USRA/SRSRA/URSRA/SRI. specgen derives bits/mask empirically by varying registers AND the shift (canon = operand bits zero; other extreme sets all shift bits), so per-arrangement immh discrimination + the growing shift-field width fall out automatically.
Verified end-to-end: encode matches llvm-mc byte-for-byte AND decode recovers mnemonic + amount (sshr/shl/sli/ushr/srsra across B/H/S/D); arm64 check + 461 tests pass.
First of the encoder-extension phase ([[rexcode-encode-coverage]]); CCMP_IMM imm5@20:16 pattern generalizes here.
Adds 14 mnemonics (74 forms) via specgen: integer two-register ABS/NEG, and the FP vector-convert (register form) family FCVTAS/AU/MS/MU/NS/NU/PS/PU/ZS/ZU + SCVTF/UCVTF. SP/DP .NEON, half-precision .FP16; the fixed-point (#fbits) convert forms come later with the immediate phase.
Verified: decode round-trips incl. FP16 (abs/neg/fcvtzs.8h/scvtf), arm64 check + 461 tests pass.
Adds 24 more mixed-arrangement mnemonics (72 forms) via specgen: three-different wide (SADDW/UADDW/SSUBW/USUBW), narrowing-halving (ADDHN/SUBHN/RADDHN/RSUBHN), and two-register narrowing (XTN/SQXTN/UQXTN/SQXTUN), plus their high-half '2' variants. All register-only (VD/VN/VM or VD/VN), no encoder change.
specgen refactored to a general arrangement-tuple mechanism (uniform + long/wide/narrow/XTN share one emit path). Verified: decode round-trips (SADDW/ADDHN/XTN/SQXTUN2), arm64 check + 461 tests pass.
Adds 26 widening long mnemonics (72 forms) via specgen: SADDL/UADDL/SSUBL/USUBL, SMULL/UMULL, SMLAL/UMLAL/SMLSL/UMLSL, SQDMULL/SQDMLAL/SQDMLSL and their high-half '2' variants. Destination arrangement is wider than the sources (Vd.8H, Vn.8B, Vm.8B; the '2' forms read the high half). Encoding stays VD/VN/VM, so no encoder change.
specgen gains a mixed-arrangement THREE_DIFF shape (low/high source-half pairs). Verified: decode round-trips (SMULL/SADDL2/SQDMULL/UMLAL), arm64 check + 461 tests pass.
Adds 10 Advanced-SIMD two-register-misc mnemonics (34 forms across valid arrangements) via specgen: NOT/RBIT/REV16/REV32/REV64/CLS/CLZ/CNT/URECPE/URSQRTE. llvm-mc filters illegal arrangements (CNT/NOT only 8B/16B, URECPE/URSQRTE only 2S/4S, ...).
specgen.lua generalized to a SHAPE table (THREE_SAME / TWO_SAME), so adding a family is one row. Verified: decode round-trips (NOT/REV64/CNT/URECPE), arm64 check + 461 tests pass.
Adds 25 Advanced-SIMD three-same integer mnemonics (153 forms across arrangements) to ENCODING_TABLE: SHADD/UHADD/SHSUB/UHSUB/SRHADD/URHADD, SQADD/UQADD/SQSUB/UQSUB, SMAX/UMAX/SMIN/UMIN, SABD/UABD/SABA/UABA, MLA/MLS, CMGE/CMHS/CMTST, SQDMULH/SQRDMULH.
Introduces tablegen/specgen.lua: compact specs (mnemonic + llvm name + arrangements) -> ENCODING_TABLE blocks, with bits taken from llvm-mc (the oracle) and mask derived empirically (vary registers 0..31). Invalid arrangements are auto-detected via llvm-mc and skipped. Output fills the SPECGEN:BEGIN..END region of encoding_table.odin in place; the hand-written core is untouched.
Verified: decode round-trips for SHADD/SQADD/CMGE/SQRDMULH; arm64 check + 461 tests pass; builders auto-generate (780 -> 805). Caveat: NEON builders currently collapse arrangements (one Register param per V operand) so inst_<mnem> exposes only the first arrangement -- an arrangement-aware builder-gen pass follows.
Author: Brendan Punsky (machine git config user.name is the login 'Flāvius').
