mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-26 02:11:36 -04:00
Alexandros Mandravillis
57f0505bd2
A renderer that keeps a screen X as SX << 16 tests the right edge against a lui-held W << 16 and the left edge with bltz on the shifted value. No explicit [widescreen.cull] kind fits either: bltz_sites compares the whole register with -margin, and a lui at a screen_x site was a build error. screen_x_sites now also takes lui rt, W -> rt = (W + margin) << 16 bltz x, outside -> taken while SX < -margin (x = SX << 16) Both are the identity at 4:3. The helpers are defined for native code and for overlay shards; their math is in ws_cull_edge.h. The two prototypes are written only for a config that lists screen_x_sites, so the generated code of every other title is unchanged.
99 lines
3.8 KiB
C
99 lines
3.8 KiB
C
#ifndef PSX_WS_CULL_EDGE_H
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#define PSX_WS_CULL_EDGE_H
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/* ============================================================================
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* Exact screen-X edge widening for explicit [widescreen.cull] site kinds
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*
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* Self-contained (depends only on <stdint.h>) so one implementation is shared
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* by the runtime helpers in gpu.c (native code and the dirty-RAM interpreter
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* both call those) and by the recompiler's unit test.
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*
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* `m` is the live per-side reveal, psx_ws_x_margin(): zero at 4:3, so every
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* function is the identity there and faithful builds are unchanged.
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*
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* bgez_sites -- `bgez SX, keep` in a signed per-vertex left-edge chain:
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*
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* bgez x0, keep ; any vertex with SX >= 0 keeps the primitive
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* bgez x1, keep
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* bgez x2, keep
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* bltz x3, reject ; only reached when x0..x2 < 0
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*
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* The final `bltz` is the existing bltz_sites kind (reject iff SX < -m). On
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* its own it is not exact: a quad with x0 in [-m, 0) and x3 < -m is still
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* rejected, although vertex 0 lies in the revealed band. Widening every
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* `bgez` to SX >= -m restores "reject iff every vertex is left of -m".
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*
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* clip_edge_x_load_sites -- a load of a screen-X clip bound (lh/lhu/lw) that
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* a renderer compares its projected vertices against:
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*
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* lh xmax, 0x70(a0) ; e.g. a scratchpad clip rectangle
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* slt at, xmax, SX ; ... reject if every SX > xmax
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*
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* A bound equal to the screen's left edge (0) moves to -m and one equal to
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* its right edge (W) moves to W+m. Any other value is an interior viewport
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* edge (a rear-view mirror, one half of a split screen) and stays unchanged,
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* so interior viewports keep their vanilla culls while full-width viewports
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* widen on each side that touches the display edge.
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*
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* screen_x_sites on `lui` and `bltz` -- a screen X kept in the high half of
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* a register (`SX << 16`), as a renderer does when it tests the sign of
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* differences and masks whole points at once:
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*
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* lui edge, W ; right screen edge as W << 16
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* sll x, sx, 16
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* sub t, x, edge ; t >= 0: the point is right of the screen
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* ...
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* bltz x, outside ; the point is left of the screen
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*
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* The `lui` moves to (W + m) << 16 and the `bltz` is taken only while
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* SX < -m. bltz_sites does not fit this `bltz`: it compares the whole
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* register with -m, and every negative `SX << 16` is far below that.
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* ========================================================================== */
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* bgez predicate (1 = branch taken = keep) for a signed screen X. */
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static inline int psx_ws_cull_bgez_value(int32_t v, int32_t m)
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{
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return v >= -(m > 0 ? m : 0);
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}
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/* Widened clip bound. `v` is the loaded value as the guest sees it
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* (sign-extended for lh, zero-extended for lhu). The result is a signed
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* 32-bit screen X in two's complement. */
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static inline uint32_t psx_ws_clip_edge_x_value(uint32_t v, uint32_t w,
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int32_t m)
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{
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if (m <= 0) return v;
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if (v == 0u) return (uint32_t)(-m);
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if (v == w) return (uint32_t)((int32_t)w + m);
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return v;
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}
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/* Widened value of `lui rt, imm` when imm is a screen-X edge in pixels: a
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* right edge (imm > 0) moves right by m, a left edge (imm < 0) moves left by
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* m. `imm` is the 16-bit immediate as encoded. */
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static inline uint32_t psx_ws_cull_lui_hi_value(uint32_t imm, int32_t m)
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{
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int32_t edge = (int32_t)(int16_t)(uint16_t)imm;
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if (m > 0) {
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if (edge > 0) edge += m;
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else if (edge < 0) edge -= m;
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}
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return (uint32_t)edge << 16;
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}
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/* bltz predicate (1 = branch taken = outside) for a screen X in the high
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* half of `v`: taken while SX < -m. */
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static inline int psx_ws_cull_bltz_hi_value(uint32_t v, int32_t m)
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{
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return (int32_t)v < -((m > 0 ? m : 0) * 65536);
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}
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#ifdef __cplusplus
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}
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#endif
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#endif /* PSX_WS_CULL_EDGE_H */
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