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reviewed: resolve_look_at__populate_proc

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ed
2026-08-15 21:34:55 -04:00
parent d9b9241e2c
commit 3301826f5c
4 changed files with 80 additions and 79 deletions
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code/hello_camera/hello_camera.atom.c
+25 -63
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@@ -273,7 +273,6 @@ internal MipsAtom* resolve_look_at__cross_uz_ux_to_up_proc(AtomArena_R aa,
/* Load a (uz).x/y/z into r.a. */
mac_load_v3s4(r.a, r.uz, 0), LdSlot_ nop,
/* Load b (ux).x/y/z into r.b. */
mac_load_v3s4(r.b, r.ux, 0), LdSlot_ /* taken by gte_mv_from_ctrl_r */
@@ -321,76 +320,39 @@ internal MipsAtom* resolve_look_at__cross_uz_ux_to_up_proc(AtomArena_R aa,
typedef Struct_(Binds_ResolveLookAtPopAndTrans) {
U4 look_at; /* U4 (MT3_S2S4* — destination matrix address) */
};
/* Atom 6 in the bundle: write look_at->m[][] from ux/uy/uz, then compute the translation column t[] = R * (-eye).
typedef Struct_(RegUse_resolve_look_at__populate_proc) {
Reg const scratch;
Reg look_at;
Reg_(V3_S4) row; /* one matrix row, reused */
Reg ux;
Reg uy;
Reg uz;
};
/* Atom 6a: write look_at->m[][] from ux/uy/uz as S2. Zero t[].
* MT3_S2S4 { A3x3_S2 m; A3_S4 t; }
* m[][] is S2 packed (9 × 2 = 18 bytes at offset 0)
* t[0/1/2] is S4 (3 × 4 = 12 bytes at offset 18)
*
* GPR codes (assigned by resolve_look_at_init):
* r_look_at : MT3_S2S4* (popped from tape; output matrix destination)
* r_pux : pointer to ux (offset O_(ResolveLookAtScratch,ux))
* r_puy : pointer to uy (offset O_(ResolveLookAtScratch,uy))
* r_puz : pointer to uz (offset O_(ResolveLookAtScratch,uz))
* r_peye : pointer to eye (offset O_(ResolveLookAtScratch,eye))
* r_tmp0/1/2 : atom-local scratch (load + MVMVA + store temps)
*
* 4 pointer regs (r_pux/r_puy/r_puz/r_peye) are DEDICATED — they hold the scratch addresses for the entire body.
* They are computed in-body via `add_si(r_px, r_scratch, O_(ResolveLookAtScratch, field))` so no tape-data pointer is needed.
*
* Struct layout (per duffle/math.h):
* MT3_S2S4 { A3x3_S2 m; A3_S4 t; } → m[][] is S2 packed (9 × 2 = 18 bytes at offset 0)
* t[0/1/2] is S4 (3 × 4 = 12 bytes at offset 18)
*
* Translation column: GTE MVMVA with the world rotation matrix pre-set
* (helper emits set_gte_world before the bundle, per the bundle design).
* MVMVA computes R * pos (with cv=0/mx=0/sf=0/v=0); MAC1/2/3 = R * (-eye).
* Pool cost: r_look_at (1) + r_scratch (R_T4 carrier) + 4 ptr regs + 3 tmp regs = 9 GPRs.
* ux/uy/uz stay dedicated address regs for the whole body.
* row is the S4 load / S2 store transfer, reused per matrix row.
* Eye is not read here — atom 6b reads it.
*/
internal MipsAtom* resolve_look_at__populate_proc(AtomArena_R aa
, U4 r_look_at
, U4 r_scratch
, U4 r_pux, U4 r_puy, U4 r_puz
, U4 r_tmp0, U4 r_tmp1, U4 r_tmp2
internal MipsAtom* resolve_look_at__populate_proc(AtomArena_R aa,
RegUse_resolve_look_at__populate_proc r
) MipsAtom_Proc_(aa, {
/* Pop look_at* (the matrix output) — advance R_TapePtr by 4 bytes. */
load_word(r_look_at, R_TapePtr, O_(Binds_ResolveLookAtPopAndTrans,look_at)),
load_word(r.look_at, R_TapePtr, O_(Binds_ResolveLookAtPopAndTrans,look_at)),
add_ui_self( R_TapePtr, S_(Binds_ResolveLookAtPopAndTrans)),
/* Compute the 3 scratch pointers in their dedicated GPRs (eye isn't needed by 6a — 6b reads it). */
add_si(r_pux, r_scratch, O_(ResolveLookAtScratch,ux)), /* r_pux = &ux */
add_si(r_puy, r_scratch, O_(ResolveLookAtScratch,uy)), /* r_puy = &uy */
add_si(r_puz, r_scratch, O_(ResolveLookAtScratch,uz)), /* r_puz = &uz */
nop,
add_si(r.ux, r.scratch, O_(ResolveLookAtScratch,ux)), /* r.ux = &ux */
add_si(r.uy, r.scratch, O_(ResolveLookAtScratch,uy)), /* r.uy = &uy */
add_si(r.uz, r.scratch, O_(ResolveLookAtScratch,uz)), /* r.uz = &uz */
/* ── m[0] = (S2)ux ── */
load_word(r_tmp0, r_pux, O_(V3_S4,x)),
load_word(r_tmp1, r_pux, O_(V3_S4,y)),
load_word(r_tmp2, r_pux, O_(V3_S4,z)),
nop,
store_half(r_tmp0, r_look_at, O_(MT3_S2S4,m[0][0])),
store_half(r_tmp1, r_look_at, O_(MT3_S2S4,m[0][1])),
store_half(r_tmp2, r_look_at, O_(MT3_S2S4,m[0][2])),
/* ── m[1] = (S2)uy ── */
load_word(r_tmp0, r_puy, O_(V3_S4,x)),
load_word(r_tmp1, r_puy, O_(V3_S4,y)),
load_word(r_tmp2, r_puy, O_(V3_S4,z)),
nop,
store_half(r_tmp0, r_look_at, O_(MT3_S2S4,m[1][0])),
store_half(r_tmp1, r_look_at, O_(MT3_S2S4,m[1][1])),
store_half(r_tmp2, r_look_at, O_(MT3_S2S4,m[1][2])),
/* ── m[2] = (S2)uz ── */
load_word(r_tmp0, r_puz, O_(V3_S4,x)),
load_word(r_tmp1, r_puz, O_(V3_S4,y)),
load_word(r_tmp2, r_puz, O_(V3_S4,z)),
nop,
store_half(r_tmp0, r_look_at, O_(MT3_S2S4,m[2][0])),
store_half(r_tmp1, r_look_at, O_(MT3_S2S4,m[2][1])),
store_half(r_tmp2, r_look_at, O_(MT3_S2S4,m[2][2])),
mac_load_v3s4(r.row, r.ux, 0), LdSlot_ mac_store_v3s2(r.row, r.look_at, O_(MT3_S2S4,m[0])),
mac_load_v3s4(r.row, r.uy, 0), LdSlot_ mac_store_v3s2(r.row, r.look_at, O_(MT3_S2S4,m[1])),
mac_load_v3s4(r.row, r.uz, 0), LdSlot_ mac_store_v3s2(r.row, r.look_at, O_(MT3_S2S4,m[2])),
/* Zero t[0..2] — atom 6c writes the final values here. */
store_word(R_0, r_look_at, O_(MT3_S2S4,t[0])),
store_word(R_0, r_look_at, O_(MT3_S2S4,t[1])),
store_word(R_0, r_look_at, O_(MT3_S2S4,t[2])),
mac_store_v3s4(v3s4_R_0(), r.look_at, O_(MT3_S2S4,t)),
mac_yield()
})