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Revert "Revert "GBA Memory: Improve gamepak prefetch timing"" 

This reverts commit 95e1dd9c35.
This commit is contained in:
Vicki Pfau 2020-01-27 18:27:43 -08:00
parent befef8ee26
commit 32827edebf
2 changed files with 7 additions and 5 deletions
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1
CHANGES
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@ -4,6 +4,7 @@ Emulation fixes:
- ARM: Fix STR storing PC after address calculation
- GBA DMA: Linger last DMA on bus (fixes mgba.io/i/301 and mgba.io/i/1320)
- GBA Memory: Misaligned SRAM writes are ignored
- GBA Memory: Improve gamepak prefetch timing
- GBA Serialize: Fix serializing DMA transfer register
- GBA Serialize: Fix audio serialization for desynced FIFOs
- GBA Serialize: Fix audio DMA timing deserialization

11
src/gba/memory.c
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@ -1626,17 +1626,19 @@ int32_t GBAMemoryStall(struct ARMCore* cpu, int32_t wait) {
maxLoads -= previousLoads;
}
int32_t s = cpu->memory.activeSeqCycles16 + 1;
int32_t s = cpu->memory.activeSeqCycles16;
int32_t n2s = cpu->memory.activeNonseqCycles16 - cpu->memory.activeSeqCycles16 + 1;
// Figure out how many sequential loads we can jam in
int32_t stall = s;
int32_t stall = s + 1;
int32_t loads = 1;
while (stall < wait && loads < maxLoads) {
stall += s;
++loads;
}
memory->lastPrefetchedPc = cpu->gprs[ARM_PC] + WORD_SIZE_THUMB * (loads + previousLoads - 1);
if (stall > wait) {
// The wait cannot take less time than the prefetch stalls
wait = stall;
@ -1645,10 +1647,9 @@ int32_t GBAMemoryStall(struct ARMCore* cpu, int32_t wait) {
// This instruction used to have an N, convert it to an S.
wait -= n2s;
memory->lastPrefetchedPc = cpu->gprs[ARM_PC] + WORD_SIZE_THUMB * (loads + previousLoads - 1);
// The next |loads|S waitstates disappear entirely, so long as they're all in a row
cpu->cycles -= (s - 1) * loads;
wait -= stall - 1;
return wait;
}