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@@ -519,8 +519,9 @@ internal MipsAtom* resolve_look_at__populate_proc(AtomArena_R aa
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mac_yield()
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})
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/* Atom 6b in the bundle: GTE matrix-vector product off = R * (-eye).
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* Reads -eye from scratch, mvmva with mx=0/cv=3/sf=1/v=3, stores MAC1/2/3 to scratch+96 (off, overwriting eye since it's no longer needed).
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/* Atom 6b in the bundle: matrix-vector product off = R * (-eye) >> 12.
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* Uses mac_apply_matrix_lv (RTPS path) which loads the RT matrix from look_at
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* and computes MAC = RT * V0 >> 12. Stores off to scratch+96 (overwriting eye).
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*
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* GPR codes (assigned by resolve_look_at_init):
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* r_scratch : R_ResolveScratch (R_T4) — scratch base
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@@ -532,38 +533,116 @@ internal MipsAtom* resolve_look_at__populate_proc(AtomArena_R aa
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internal MipsAtom* resolve_look_at__matrix_vector_proc(AtomArena_R aa
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, U4 r_scratch
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, U4 r_peye
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, U4 r_look_at
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, U4 r_tmp0, U4 r_tmp1, U4 r_tmp2
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, U4 r_tmp3, U4 r_tmp4, U4 r_tmp5
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) MipsAtom_Proc_(resolve_look_at__matrix_vector, aa, {
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/* r_peye = &eye (slot +96, will be overwritten with off after MVMVA). */
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/* r_peye = &eye (slot +96, will be overwritten with off). */
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add_si(r_peye, r_scratch, O_(ResolveLookAtScratch,eye)),
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nop,
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/* pos = -eye: load eye.x/y/z, negate via sub_u from R_0. */
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/* Load pos = -eye from scratch. */
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load_word(r_tmp0, r_peye, O_(P3_S4,x)),
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load_word(r_tmp1, r_peye, O_(P3_S4,y)),
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load_word(r_tmp2, r_peye, O_(P3_S4,z)),
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nop,
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sub_u(r_tmp0, R_0, r_tmp0), /* pos.x = -eye.x */
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sub_u(r_tmp0, R_0, r_tmp0),
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sub_u(r_tmp1, R_0, r_tmp1),
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sub_u(r_tmp2, R_0, r_tmp2),
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/* mtc2 IR1/2/3 = pos (for MVMVA input). */
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/* Pop look_at* from tape for RT matrix loading. */
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load_word(r_look_at, R_TapePtr, O_(Binds_ResolveLookAtPopAndTrans,look_at)),
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add_ui_self( R_TapePtr, S_(Binds_ResolveLookAtPopAndTrans)),
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/* Load RT matrix from look_at into C2[0..4] via ctc2.
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* Uses the interleaved load+ctc2 pattern (same as set_gte_mt3s2s4
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* and libgte's ApplyMatrixLV): load 2 words, ctc2 both, etc.
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* MT3_S2S4 stores m[i][j] as S2 (16-bit) packed row-major. */
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load_word( r_tmp3, r_look_at, 0), load_word( r_tmp4, r_look_at, 4),
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gte_mv_to_ctrl_r(r_tmp3, gte_cr_RT11), gte_mv_to_ctrl_r(r_tmp4, gte_cr_RT12),
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load_word( r_tmp3, r_look_at, 8), load_word( r_tmp4, r_look_at, 12), load_word(r_tmp5, r_look_at, 16),
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gte_mv_to_ctrl_r(r_tmp3, gte_cr_RT13), gte_mv_to_ctrl_r(r_tmp4, gte_cr_RT21), gte_mv_to_ctrl_r(r_tmp5, gte_cr_RT22),
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nop2,
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/* === Two-pass MVMVA decomposition (replicates libgte's ApplyMatrixLV) ===
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* Pass 1: RT · (pos >> 15) with sf=0 → contributes (result << 3) to final.
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* Pass 2: RT · (pos & 0x7FFF) with sf=1 → contributes (result >> 12) to final.
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* Combined: final = (pass1 << 3) + pass2 = (RT · pos) >> 12.
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* pos is in r_tmp0/1/2 (S4, 32-bit). High bits → r_tmp3/4/5. Low bits →
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* back into r_tmp0/1/2 (reusing pos slots since they're consumed).
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*
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* For pos fitting in S16 range (|pos| < 32768), pos >> 15 = 0 for
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* positive and -1 for negative. SRA fills with sign bit, so
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* shift_aright gives the correct high bits directly.
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* For low bits: negu + andi 0x7FFF + negu preserves sign.
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* Since the full decomposition for 3 components needs branches and
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* more GPRs than we have, and for |pos| < 32768 the high bits are
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* just 0 or -1, we simplify: pass1 = RT · {0 or -1} << 3. */
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/* pos.x decomposition: high = pos.x >> 15 (SRA, sign-fills).
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* Low bits = pos.x & 0x7FFF with sign preserved.
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* For |pos| < 32768, high = 0 (positive) or -1 (negative). */
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shift_aright_var(r_tmp3, r_tmp0, 15), /* r_tmp3 = pos.x >> 15 (SRA) */
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/* Low bits: if negative, negu+andi+negu; if positive, just andi.
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* For S16-fitting values, andi 0x7FFF preserves bit 15 via the
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* negu dance. But since pos.x fits in S16 for our case,
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* we can just use pos.x & 0x7FFF and OR with the sign bit:
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* low = (pos.x & 0x7FFF) | (pos.x & 0x8000).
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* Simpler: for our camera positions, pos fits in S16 so the
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* negu+andi+negu pattern just gives pos.x back. We can skip it
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* and use pos.x directly for pass 2 IR input. */
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/* r_tmp0 still has pos.x (S4, 32-bit). Pass 2 needs S16 in IR. */
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/* mtc2 IR1/2/3 = high bits. */
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gte_mv_to_data_r(r_tmp3, C2_IR1),
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gte_mv_to_data_r(r_tmp4, C2_IR2),
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gte_mv_to_data_r(r_tmp5, C2_IR3),
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nop2, /* MTC2 retirement */
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/* Pass 1 MVMVA: sf=0 (no shift), v=3 (IR), cv=3 (no TR), mx=0 (RT). */
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gte_cmdw_mvmva_sf0_ir,
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nop,
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/* mfc2 MAC1/2/3 → r_tmp3/4/5 (pass 1 results). */
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gte_mv_from_data_r(r_tmp3, C2_MAC1),
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gte_mv_from_data_r(r_tmp4, C2_MAC2),
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gte_mv_from_data_r(r_tmp5, C2_MAC3),
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nop,
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/* mtc2 IR1/2/3 = low bits.
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* For S16-fitting pos, the low bits are just pos & 0x7FFF with
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* sign preserved. Since pos.x = -eye.x fits in S16 for camera
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* positions, we can use pos.x & 0xFFFF (which preserves the sign
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* bit via the full 32-bit value). The GTE takes low 16 bits. */
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and_i(r_tmp0, r_tmp0, 0xFFFF), /* pos.x low 16 bits */
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and_i(r_tmp1, r_tmp1, 0xFFFF), /* pos.y low 16 bits */
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and_i(r_tmp2, r_tmp2, 0xFFFF), /* pos.z low 16 bits */
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gte_mv_to_data_r(r_tmp0, C2_IR1),
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gte_mv_to_data_r(r_tmp1, C2_IR2),
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gte_mv_to_data_r(r_tmp2, C2_IR3),
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nop2,
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/* MVMVA: sf=1 (integer, no shift), cv=3 (no TR), mx=0 (rotation matrix),
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* v=3 (IR vector). Pre-set rotation matrix is the one set by set_gte_world. */
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/* Pass 2 MVMVA: sf=1 (>>12), v=3 (IR), cv=3 (no TR), mx=0 (RT). */
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gte_cmdw_mvmva_ir,
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nop, /* GTE interlock */
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nop,
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/* mfc2 MAC1/2/3 → r_tmp0/r_tmp1/r_tmp2 (sign-extended into 32-bit GPRs). */
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/* mfc2 MAC1/2/3 → r_tmp0/1/2 (pass 2 results). */
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gte_mv_from_data_r(r_tmp0, C2_MAC1),
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gte_mv_from_data_r(r_tmp1, C2_MAC2),
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gte_mv_from_data_r(r_tmp2, C2_MAC3),
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nop,
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/* Combine: final = (pass1 << 3) + pass2.
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* shift_lleft shifts left by 3. Since pass1 result fits in
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* GPR (32-bit), sll by 3 is safe (worst case: shifts sign bit
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* out, which is fine for the >>12 result). */
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shift_lleft(r_tmp3, r_tmp3, 3),
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add_u(r_tmp0, r_tmp0, r_tmp3),
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shift_lleft(r_tmp4, r_tmp4, 3),
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add_u(r_tmp1, r_tmp1, r_tmp4),
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shift_lleft(r_tmp5, r_tmp5, 3),
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add_u(r_tmp2, r_tmp2, r_tmp5),
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/* Store off → scratch+96 (overwriting eye). Atom 6c reads from here. */
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store_word(r_tmp0, r_peye, O_(V3_S4,x)),
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store_word(r_tmp1, r_peye, O_(V3_S4,y)),
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