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lr-snes9x/cpuexec.cpp
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LibretroAdmin 97c65a34a2 SuperFX: backport the remaining snes9xgit GSU fixes 
Backport survey against snes9xgit master through 2ab06b3, covering the
shanytc GSU/IRQ series and its adjacent correctness fixes. Two of the
four core items were already here: the cycle-accurate GSU timing model
itself (8783b54 + OV2's 1994532 follow-up) landed earlier as the
snes9x_superfx_timing core option - the libretro equivalent of the
settings-file/command-line switch OV2 added - and the $4211 pending-IRQ
latch (c0dffce) is already in ppu.cpp. The two that were missing land
here.

1. Winter Gold pose-cel hold (the #533 half of 8783b54/1994532).

At the race-start pose switch the game polls the GSU-published pose cel
at $70:EBC0 once per frame and commits the skier arrangement from it.
The scanline-batch model publishes one frame earlier than hardware, so a
stale arrangement is committed over the new pose tiles - the garbled
skier. Hold CPU visibility of the 0 -> nonzero publish transition for
fx_cel_delay lines (312, one frame, matching upstream's Mesen2-verified
figure), set only for FX SKIING NINTENDO 96 by ApplyROMFixes.

Two deliberate divergences from upstream's shim: the hold is ticked from
the per-line event in cpuexec rather than inside S9xSuperFXExec, because
this port only calls the exec with GO set and the publish happens
precisely when the GSU stops - a hold counted there would freeze the
moment it mattered; and a republish during the hold window is captured
and restored when the hold expires rather than lost. The hold state
lives in FxRegs_s beside vHwFillMask and like it is deliberately not
serialized: a savestate landing inside the window at worst re-times that
one publish by a frame, in one handshake of one game.

2. RPIX stops clearing DREG too early (c1aa979, snes9xgit#1055/#1056).

CLRFLAGS resets pvDreg/pvSreg to R0, and all three rpix variants ran it
before storing the result. With a TO rn prefix the pixel read therefore
landed in R0 instead of rn, and TESTR14 tested the stale pointer, so TO
R14 : RPIX failed to re-trigger the ROM buffer read. Move CLRFLAGS after
the stores and TESTR14, the order every other DREG-writing op already
uses (fx_swap is the pattern). fx_rpix_obj is an empty stub here and
needs nothing.

Not taken, with reasons: the win32 commits (59d6c2b, fa20c02, 9cd4c1b)
are frontend-only; the 11MB SuperFX mapper (3813bf5) and UPS bounds
check (96b3661) are not part of the shanytc series and can ride a later
sync.

Builds clean through the LTO link.
2026-08-11 06:51:51 +02:00

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/*****************************************************************************\
Snes9x - Portable Super Nintendo Entertainment System (TM) emulator.
This file is licensed under the Snes9x License.
For further information, consult the LICENSE file in the root directory.
\*****************************************************************************/
#include "snes9x.h"
#include "memmap.h"
#include "cpuops.h"
#include "dma.h"
#include "apu/apu.h"
#include "fxemu.h"
#include "srtc.h"
#include "spc7110.h"
#include "bsflash.h"
#include "snapshot.h"
#ifdef DEBUGGER
#include "debug.h"
#include "missing.h"
#endif
static inline void S9xReschedule (void);
void S9xMainLoop (void)
{
#define CHECK_FOR_IRQ_CHANGE() \
if (Timings.IRQFlagChanging) \
{ \
if (Timings.IRQFlagChanging & IRQ_TRIGGER_NMI) \
{ \
CPU.NMIPending = TRUE; \
Timings.NMITriggerPos = CPU.Cycles + 6; \
} \
if (Timings.IRQFlagChanging & IRQ_CLEAR_FLAG) \
ClearIRQ(); \
else if (Timings.IRQFlagChanging & IRQ_SET_FLAG) \
SetIRQ(); \
Timings.IRQFlagChanging = IRQ_NONE; \
}
if (CPU.Flags & SCAN_KEYS_FLAG)
{
CPU.Flags &= ~SCAN_KEYS_FLAG;
}
for (;;)
{
if (CPU.NMIPending)
{
#ifdef DEBUGGER
if (Settings.TraceHCEvent)
S9xTraceFormattedMessage ("Comparing %d to %d\n", Timings.NMITriggerPos, CPU.Cycles);
#endif
if (Timings.NMITriggerPos <= CPU.Cycles)
{
CPU.NMIPending = FALSE;
Timings.NMITriggerPos = 0xffff;
if (CPU.WaitingForInterrupt)
{
CPU.WaitingForInterrupt = FALSE;
Registers.PCw++;
CPU.Cycles += TWO_CYCLES + ONE_DOT_CYCLE / 2;
while (CPU.Cycles >= CPU.NextEvent)
S9xDoHEventProcessing();
}
CHECK_FOR_IRQ_CHANGE();
S9xOpcode_NMI();
}
}
if (CPU.Cycles >= Timings.NextIRQTimer)
{
#ifdef DEBUGGER
S9xTraceMessage ("Timer triggered\n");
#endif
S9xUpdateIRQPositions(false);
CPU.IRQLine = TRUE;
}
if (CPU.IRQLine || CPU.IRQExternal)
{
if (CPU.WaitingForInterrupt)
{
CPU.WaitingForInterrupt = FALSE;
Registers.PCw++;
CPU.Cycles += TWO_CYCLES + ONE_DOT_CYCLE / 2;
while (CPU.Cycles >= CPU.NextEvent)
S9xDoHEventProcessing();
}
if (!CheckFlag(IRQ))
{
/* The flag pushed onto the stack is the new value */
CHECK_FOR_IRQ_CHANGE();
S9xOpcode_IRQ();
}
}
/* Change IRQ flag for instructions that set it only on last cycle */
CHECK_FOR_IRQ_CHANGE();
#ifdef DEBUGGER
if ((CPU.Flags & BREAK_FLAG) && !(CPU.Flags & SINGLE_STEP_FLAG))
{
for (int Break = 0; Break != 6; Break++)
{
if (S9xBreakpoint[Break].Enabled &&
S9xBreakpoint[Break].Bank == Registers.PB &&
S9xBreakpoint[Break].Address == Registers.PCw)
{
if (S9xBreakpoint[Break].Enabled == 2)
S9xBreakpoint[Break].Enabled = TRUE;
else
CPU.Flags |= DEBUG_MODE_FLAG;
}
}
}
if (CPU.Flags & DEBUG_MODE_FLAG)
break;
if (CPU.Flags & TRACE_FLAG)
S9xTrace();
if (CPU.Flags & SINGLE_STEP_FLAG)
{
CPU.Flags &= ~SINGLE_STEP_FLAG;
CPU.Flags |= DEBUG_MODE_FLAG;
}
#endif
if (CPU.Flags & SCAN_KEYS_FLAG)
{
break;
}
uint8 Op;
struct SOpcodes *Opcodes;
if (CPU.PCBase)
{
Op = CPU.PCBase[Registers.PCw];
CPU.Cycles += CPU.MemSpeed;
Opcodes = ICPU.S9xOpcodes;
if (CPU.Cycles > 1000000)
{
CPU.Flags |= HALTED_FLAG;
S9xMessage(S9X_FATAL_ERROR, 0, "CPU is deadlocked");
return;
}
}
else
{
Op = S9xGetByte(Registers.PBPC);
OpenBus = Op;
Opcodes = S9xOpcodesSlow;
}
if ((Registers.PCw & MEMMAP_MASK) + ICPU.S9xOpLengths[Op] >= MEMMAP_BLOCK_SIZE)
{
uint8 *oldPCBase = CPU.PCBase;
CPU.PCBase = S9xGetBasePointer(ICPU.ShiftedPB + ((uint16) (Registers.PCw + 4)));
if (oldPCBase != CPU.PCBase || (Registers.PCw & ~MEMMAP_MASK) == (0xffff & ~MEMMAP_MASK))
Opcodes = S9xOpcodesSlow;
}
Registers.PCw++;
(*Opcodes[Op].S9xOpcode)();
if (Settings.SA1)
S9xSA1MainLoop();
}
S9xPackStatus();
}
static inline void S9xReschedule (void)
{
switch (CPU.WhichEvent)
{
case HC_HBLANK_START_EVENT:
CPU.WhichEvent = HC_HDMA_START_EVENT;
CPU.NextEvent = Timings.HDMAStart;
break;
case HC_HDMA_START_EVENT:
CPU.WhichEvent = HC_HCOUNTER_MAX_EVENT;
CPU.NextEvent = Timings.H_Max;
break;
case HC_HCOUNTER_MAX_EVENT:
CPU.WhichEvent = HC_HDMA_INIT_EVENT;
CPU.NextEvent = Timings.HDMAInit;
break;
case HC_HDMA_INIT_EVENT:
CPU.WhichEvent = HC_RENDER_EVENT;
CPU.NextEvent = Timings.RenderPos;
break;
case HC_RENDER_EVENT:
CPU.WhichEvent = HC_WRAM_REFRESH_EVENT;
CPU.NextEvent = Timings.WRAMRefreshPos;
break;
case HC_WRAM_REFRESH_EVENT:
CPU.WhichEvent = HC_HBLANK_START_EVENT;
CPU.NextEvent = Timings.HBlankStart;
break;
}
}
void S9xDoHEventProcessing (void)
{
#ifdef DEBUGGER
static char eventname[7][32] =
{
"",
"HC_HBLANK_START_EVENT",
"HC_HDMA_START_EVENT ",
"HC_HCOUNTER_MAX_EVENT",
"HC_HDMA_INIT_EVENT ",
"HC_RENDER_EVENT ",
"HC_WRAM_REFRESH_EVENT"
};
#endif
#ifdef DEBUGGER
if (Settings.TraceHCEvent)
S9xTraceFormattedMessage("--- HC event processing (%s) expected HC:%04d executed HC:%04d VC:%04d",
eventname[CPU.WhichEvent], CPU.NextEvent, CPU.Cycles, CPU.V_Counter);
#endif
switch (CPU.WhichEvent)
{
case HC_HBLANK_START_EVENT:
S9xReschedule();
break;
case HC_HDMA_START_EVENT:
S9xReschedule();
if (PPU.HDMA && CPU.V_Counter <= PPU.ScreenHeight)
{
#ifdef DEBUGGER
S9xTraceFormattedMessage("*** HDMA Transfer HC:%04d, Channel:%02x", CPU.Cycles, PPU.HDMA);
#endif
PPU.HDMA = S9xDoHDMA(PPU.HDMA);
}
break;
case HC_HCOUNTER_MAX_EVENT:
if (Settings.SRTC)
S9xSRTCTick();
if (Settings.SPC7110RTC)
S9xSPC7110RTCTick();
if (Settings.BS)
S9xBSFlashTick();
if (Settings.SuperFX)
{
// The ported GSU core does not gate internally; run only
// with GO set and a bus grant, as the snes9x2010 call
// sites do (see CHECK_EXEC_SUPERFX).
if (!SuperFX.oneLineDone && CHECK_EXEC_SUPERFX())
S9xSuperFXExec();
SuperFX.oneLineDone = FALSE;
// Ticks every line, whether or not the GSU ran; see the
// comment on the function for why it cannot live in the
// exec above. No-op unless fx_cel_delay is set (FX SKIING only).
S9xSuperFXCelDelayTick();
}
S9xAPUEndScanline();
CPU.Cycles -= Timings.H_Max;
if (Timings.NMITriggerPos != 0xffff)
Timings.NMITriggerPos -= Timings.H_Max;
if (Timings.NextIRQTimer != 0x0fffffff)
Timings.NextIRQTimer -= Timings.H_Max;
S9xAPUSetReferenceTime(CPU.Cycles);
if (Settings.SA1)
SA1.Cycles -= Timings.H_Max * 3;
CPU.V_Counter++;
if (CPU.V_Counter >= Timings.V_Max) // V ranges from 0 to Timings.V_Max - 1
{
CPU.V_Counter = 0;
// From byuu:
// [NTSC]
// interlace mode has 525 scanlines: 263 on the even frame, and 262 on the odd.
// non-interlace mode has 524 scanlines: 262 scanlines on both even and odd frames.
// [PAL] <PAL info is unverified on hardware>
// interlace mode has 625 scanlines: 313 on the even frame, and 312 on the odd.
// non-interlace mode has 624 scanlines: 312 scanlines on both even and odd frames.
if (IPPU.Interlace && S9xInterlaceField())
Timings.V_Max = Timings.V_Max_Master + 1; // 263 (NTSC), 313?(PAL)
else
Timings.V_Max = Timings.V_Max_Master; // 262 (NTSC), 312?(PAL)
Memory.FillRAM[0x213F] ^= 0x80;
PPU.RangeTimeOver = 0;
// FIXME: reading $4210 will wait 2 cycles, then perform reading, then wait 4 more cycles.
Memory.FillRAM[0x4210] = Model->_5A22;
ICPU.Frame++;
PPU.HVBeamCounterLatched = 0;
}
// From byuu:
// In non-interlace mode, there are 341 dots per scanline, and 262 scanlines per frame.
// On odd frames, scanline 240 is one dot short.
// In interlace mode, there are always 341 dots per scanline. Even frames have 263 scanlines,
// and odd frames have 262 scanlines.
// Interlace mode scanline 240 on odd frames is not missing a dot.
if (CPU.V_Counter == 240 && !IPPU.Interlace && S9xInterlaceField()) // V=240
Timings.H_Max = Timings.H_Max_Master - ONE_DOT_CYCLE; // HC=1360
else
Timings.H_Max = Timings.H_Max_Master; // HC=1364
if (Model->_5A22 == 2)
{
if (CPU.V_Counter != 240 || IPPU.Interlace || !S9xInterlaceField()) // V=240
{
if (Timings.WRAMRefreshPos == SNES_WRAM_REFRESH_HC_v2 - ONE_DOT_CYCLE) // HC=534
Timings.WRAMRefreshPos = SNES_WRAM_REFRESH_HC_v2; // HC=538
else
Timings.WRAMRefreshPos = SNES_WRAM_REFRESH_HC_v2 - ONE_DOT_CYCLE; // HC=534
}
}
else
Timings.WRAMRefreshPos = SNES_WRAM_REFRESH_HC_v1;
if (CPU.V_Counter == PPU.ScreenHeight + FIRST_VISIBLE_LINE) // VBlank starts from V=225(240).
{
S9xEndScreenRefresh();
#ifdef DEBUGGER
if (!(CPU.Flags & FRAME_ADVANCE_FLAG))
#endif
{
S9xSyncSpeed();
}
CPU.Flags |= SCAN_KEYS_FLAG;
PPU.HDMA = 0;
// Bits 7 and 6 of $4212 are computed when read in S9xGetPPU.
#ifdef DEBUGGER
missing.dma_this_frame = 0;
#endif
IPPU.MaxBrightness = PPU.Brightness;
PPU.ForcedBlanking = (Memory.FillRAM[0x2100] >> 7) & 1;
if (!PPU.ForcedBlanking)
{
PPU.OAMAddr = PPU.SavedOAMAddr;
uint8 tmp = 0;
if (PPU.OAMPriorityRotation)
tmp = (PPU.OAMAddr & 0xFE) >> 1;
if ((PPU.OAMFlip & 1) || PPU.FirstSprite != tmp)
{
PPU.FirstSprite = tmp;
IPPU.OBJChanged = TRUE;
}
PPU.OAMFlip = 0;
}
// FIXME: writing to $4210 will wait 6 cycles.
Memory.FillRAM[0x4210] = 0x80 | Model->_5A22;
if (Memory.FillRAM[0x4200] & 0x80)
{
#ifdef DEBUGGER
if (Settings.TraceHCEvent)
S9xTraceFormattedMessage ("NMI Scheduled for next scanline.");
#endif
// FIXME: triggered at HC=6, checked just before the final CPU cycle,
// then, when to call S9xOpcode_NMI()?
CPU.NMIPending = TRUE;
Timings.NMITriggerPos = 6 + 6;
}
}
if (CPU.V_Counter == PPU.ScreenHeight + 3) // FIXME: not true
{
if (Memory.FillRAM[0x4200] & 1)
S9xDoAutoJoypad();
}
if (CPU.V_Counter == FIRST_VISIBLE_LINE) // V=1
S9xStartScreenRefresh();
S9xReschedule();
break;
case HC_HDMA_INIT_EVENT:
S9xReschedule();
if (CPU.V_Counter == 0)
{
#ifdef DEBUGGER
S9xTraceFormattedMessage("*** HDMA Init HC:%04d, Channel:%02x", CPU.Cycles, PPU.HDMA);
#endif
S9xStartHDMA();
}
break;
case HC_RENDER_EVENT:
if (CPU.V_Counter >= FIRST_VISIBLE_LINE && CPU.V_Counter <= PPU.ScreenHeight)
RenderLine((uint8) (CPU.V_Counter - FIRST_VISIBLE_LINE));
S9xReschedule();
break;
case HC_WRAM_REFRESH_EVENT:
#ifdef DEBUGGER
S9xTraceFormattedMessage("*** WRAM Refresh HC:%04d", CPU.Cycles);
#endif
CPU.Cycles += SNES_WRAM_REFRESH_CYCLES;
S9xReschedule();
break;
}
#ifdef DEBUGGER
if (Settings.TraceHCEvent)
S9xTraceFormattedMessage("--- HC event rescheduled (%s) expected HC:%04d current HC:%04d",
eventname[CPU.WhichEvent], CPU.NextEvent, CPU.Cycles);
#endif
}
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