M CHANGES → CHANGES

@@ -17,6 +17,7 @@ - GB MBC: Fix MBC2 saves (fixes mgba.io/i/954)
  - GBA Memory: Fix copy-on-write memory leak
  - Core: Fix ROM patches not being unloaded when disabled (fixes mgba.io/i/962)
  - GBA I/O: Fix writing to DISPCNT CGB flag (fixes mgba.io/i/902)
+ - GBA Memory: Partially revert prefetch changes (fixes mgba.io/i/840)
 Misc:
  - GBA: Improve multiboot image detection
  - GB MBC: Remove erroneous bank 0 wrapping

M src/gba/memory.c → src/gba/memory.c

@@ -1506,8 +1506,8 @@ previousLoads = dist >> 1;
 		maxLoads -= previousLoads;
 	}
 
-	int32_t s = cpu->memory.activeSeqCycles16;
-	int32_t n2s = cpu->memory.activeNonseqCycles16 - cpu->memory.activeSeqCycles16;
+	int32_t s = cpu->memory.activeSeqCycles16 + 1;
+	int32_t n2s = cpu->memory.activeNonseqCycles16 - cpu->memory.activeSeqCycles16 + 1;
 
 	// Figure out how many sequential loads we can jam in
 	int32_t stall = s;
@@ -1528,7 +1528,7 @@
 	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 -= stall;
+	cpu->cycles -= (s - 1) * loads;
 	return wait;
 }