psxrecomp/runtime/include/overlay_api.h

#ifndef OVERLAY_API_H
#define OVERLAY_API_H

/* Shared ABI between psx-runtime.exe and overlay DLLs.
 *
 * After LoadLibrary, the runtime calls overlay_init() with this struct.
 * The DLL stores the pointers and routes all cross-module calls through them.
 */

#include "cpu_state.h"
#include <stdint.h>

/* ABI version exported by every overlay DLL as `overlay_abi()`.  The loader
 * rejects (and deletes, so autocompile regenerates) any DLL whose version
 * doesn't match — including all pre-versioning DLLs, which lack the export.
 *
 * v2: dispatch call-contract (Bug D family) — DLL call sites carry (ra, sp)
 *     contract checks and share the runtime's bail state via the appended
 *     callback pointers below.
 * v3: widescreen backdrop screenX squash ([widescreen.backdrop] x_sites) —
 *     overlay backdrop handlers now emit psx_ws_backdrop_x() at their screenX
 *     store. This is an EMIT-content change (not a struct-ABI change), but the
 *     version is the cache discriminator: bumping it forces the loader to
 *     reject pre-backdrop DLLs so autocompile regenerates them with the squash.
 *     (The deferred follow-up is to auto-derive this tag from a hash of the
 *     widescreen config + emit headers; until then it's a manual bump.)
 * v4: widescreen backdrop column PRELOAD ([widescreen.cull] auto_backdrop) —
 *     overlay backdrop generators now emit psx_ws_backdrop_value() at the
 *     window START/END finalize, and the callback struct grows a
 *     ws_backdrop_value pointer (appended last). Bumping rejects pre-preload
 *     DLLs (which lack both the emit and a host that supplies the callback). */
/*   v5: psx_syscall callback return type void->int (CPS, RECURSION_BUG.md §25);
 *       overlays compiled under CPS emit `if (psx_syscall(...)) return;`. */
#define PSX_OVERLAY_ABI_VERSION 5

/* Codegen flavor of the recompiled output the overlays + runtime were built
 * against. Overlays are keyed in the cache by guest-bytes CRC, which is
 * flavor-BLIND — the same guest overlay yields the same filename whether it was
 * compiled by the base recompiler or a variant (e.g. widescreen, which emits
 * extra runtime symbols + GTE adjustments). Without a flavor tag a widescreen
 * DLL and a base DLL for the same overlay collide. The flavor is folded into
 * overlay_abi() (high 16 bits) so the loader's existing ABI gate rejects (and
 * regenerates) any DLL whose flavor differs from the running build's, keeping
 * caches separate even in a shared directory.
 *
 * Base/master MUST stay 0 so the tag == PSX_OVERLAY_ABI_VERSION (backward
 * compatible with all existing base-flavor DLLs). A variant build overrides it
 * (e.g. -DPSX_OVERLAY_FLAVOR=1 for widescreen) for BOTH the runtime and
 * compile_overlays.py (its --flavor arg). */
#ifndef PSX_OVERLAY_FLAVOR
#define PSX_OVERLAY_FLAVOR 0
#endif

/* Combined tag exported by overlay_abi() and checked by the loader. */
#define PSX_OVERLAY_ABI_TAG \
    ((int)((PSX_OVERLAY_ABI_VERSION & 0xFFFF) | ((PSX_OVERLAY_FLAVOR & 0xFFFF) << 16)))

/* Codegen version — bumped whenever the recompiler emits DIFFERENT bytes for the
 * same guest overlay WITHOUT an ABI change (the load-time overlay_abi() gate only
 * catches ABI/flavor changes; a pure-emitter change produces a different DLL the
 * gate would happily accept). The cache is namespaced by this version
 * (gcc/<arch-abi>/cg<N>/), so a build with new codegen writes + reads a FRESH
 * directory and never reuses a stale DLL; old versions coexist on disk (no
 * auto-delete — a user who downgrades still finds their matching cache). Python
 * (compile_overlays.py) parses this same constant from this header, so the two
 * sides can never drift. BUMP THIS when you change code_generator.cpp emit in a
 * way that alters overlay output (e.g. the auto_screen_x widescreen widening).
 *   1: baseline + auto_screen_x render-funnel cull via psx_ws_cull_sltiu.
 *   2: + auto_backdrop far-backdrop column preload via psx_ws_backdrop_value.
 *   3: auto_backdrop switched to camera-tracked window WIDENING
 *      (psx_ws_backdrop_value gains a window_cols arg).
 *   4: continuation-passing (PSX_CPS, RECURSION_BUG.md §25) — overlay funcs
 *      tail-transfer + carry an entry-switch; the loader routes continuations.
 *      Fresh namespace so CPS DLLs never reuse a legacy (unit-model) cg3 DLL. */
#define PSX_OVERLAY_CODEGEN_VER 4

typedef struct {
    /* Core dispatch: routes call_by_address() and out-of-overlay jal */
    void (*dispatch_call)(CPUState *cpu, uint32_t addr, uint32_t ra);
    /* Interrupt check: called after every function return in overlay */
    void (*check_interrupts)(CPUState *cpu);
    /* GTE coprocessor 2 execution */
    void (*gte_execute)(CPUState *cpu, uint32_t cmd);
    /* MIPS syscall (break/syscall instructions). Returns 1 if control
     * transfers (cpu->pc set), 0 for a directly-handled void syscall. See
     * cpu_state.h. The signature changed with CPS (RECURSION_BUG.md §25), so
     * PSX_OVERLAY_ABI_VERSION was bumped to reject stale overlay caches. */
    int  (*psx_syscall)(CPUState *cpu, uint32_t code);
    /* Unresolved dispatch target */
    void (*psx_unknown_dispatch)(CPUState *cpu, uint32_t addr, uint32_t phys);
    /* Debug instrumentation: called at every function entry (may be NULL) */
    void (*log_call_entry)(uint32_t func_addr);
    /* RestoreState/ReturnFromException longjmp escape (interrupts.c). The
     * recompiler emits this at longjmp-return sites in exception-context
     * kernel code (the install-slot / kernel-window class). Appended LAST:
     * overlay_init copies the struct by value, so older DLLs built against
     * the shorter struct simply never read this member. */
    void (*psx_restore_state_escape)(void);
    /* Call-contract state shared with the runtime (ABI v2; see the contract
     * model in cpu_state.h).  DLL code reads the bail flag and bumps the
     * counters through these pointers. */
    int      *call_bail_flag;
    uint64_t *bail_first;
    uint64_t *bail_resolved;
    /* Widescreen hooks (ABI v3). The recompiler can emit psx_ws_* calls into
     * OVERLAY code (backdrop screenX squash; and, for other games, sprite-tag
     * or cull sites that resolve into overlays). These compute against the
     * host's live widescreen state (gpu.c), so the DLL forwards to the runtime
     * through these. Appended LAST (struct grows back-compatibly); may be NULL
     * on a host that predates them — the DLL glue falls back to identity. */
    int  (*ws_backdrop_x)(int x);
    int  (*ws_x_margin)(void);
    void (*ws_sprite_tag)(CPUState *cpu);
    /* Widescreen backdrop column-preload value substitution (ABI v4). Overlay
     * backdrop generators call this at a detected window START/END bound; the
     * runtime returns `orig` unless native-wide is engaged, in which case it
     * widens the camera-tracked window by the 16:9 reveal (START -> orig-margin,
     * END -> orig+margin; margin scales with window_cols). Appended LAST (struct
     * grows back-compatibly); may be NULL on a host that predates it — the DLL
     * glue falls back to orig. */
    uint32_t (*ws_backdrop_value)(uint32_t orig, int is_end, int window_cols);
} OverlayCallbacks;

#ifdef __cplusplus
extern "C" {
#endif

/* Exported by every overlay DLL.  Call once after LoadLibrary. */
#ifdef _WIN32
__declspec(dllexport)
#else
__attribute__((visibility("default")))
#endif
void overlay_init(const OverlayCallbacks *cbs);

#ifdef __cplusplus
}
#endif

#endif /* OVERLAY_API_H */