SCI: Added a custom modulo reg_t operator

This version only handles signed integers. The modulo operator was changed in
SCI0 late (Iceman, and perhaps all SCI0 0.000.685 and later) so that it handles
negative numbers as well. We need to see if there really is a need to keep two
different modulo operators (which will only be necessary if any SCI0 game asks
for the modulo of a negative number by mistake, or a number larger than 32767).
Thus, error out in such a case for SCI0, so that this can be investigated
properly

1 files changed, 3 insertions, 21 deletions

diff --git a/engines/sci/engine/vm.cpp b/engines/sci/engine/vm.cpp
index a6677ee633..69d046da7d 100644
--- a/engines/sci/engine/vm.cpp
+++ b/engines/sci/engine/vm.cpp
@@ -961,28 +961,10 @@ void run_vm(EngineState *s) {
 			s->r_acc = POP32() / s->r_acc;
 			break;
 
-		case op_mod: { // 0x05 (05)
-			if (getSciVersion() <= SCI_VERSION_0_LATE) {
-				uint16 modulo = s->r_acc.requireUint16();
-				uint16 value = POP32().requireUint16();
-				uint16 result = (modulo != 0 ? value % modulo : 0);
-				s->r_acc = make_reg(0, result);
-			} else {
-				// In Iceman (and perhaps from SCI0 0.000.685 onwards in general),
-				// handling for negative numbers was added. Since Iceman doesn't
-				// seem to have issues with the older code, we exclude it for now
-				// for simplicity's sake and use the new code for SCI01 and newer
-				// games. Fixes the battlecruiser mini game in SQ5 (room 850),
-				// bug #3035755
-				int16 modulo = ABS(s->r_acc.requireSint16());
-				int16 value = POP32().requireSint16();
-				int16 result = (modulo != 0 ? value % modulo : 0);
-				if (result < 0)
-					result += modulo;
-				s->r_acc = make_reg(0, result);
-			}
+		case op_mod: // 0x05 (05)
+			// we check for division by 0 inside the custom reg_t modulo operator
+			s->r_acc = POP32() % s->r_acc;
 			break;
-		}
 
 		case op_shr: // 0x06 (06)
 			// Shift right logical