dmnt: add theoretical 'else' support to cheat engine vm conditionals

docs/features/cheats.md

@@ -59,7 +59,7 @@ Code type 0x0 allows writing a static value to a memory address.
 ### Code Type 0x1: Begin Conditional Block
 Code type 0x1 performs a comparison of the contents of memory to a static value.
 
-If the condition is not met, all instructions until the appropriate conditional block terminator are skipped.
+If the condition is not met, all instructions until the appropriate End or Else conditional block terminator are skipped.
 
 #### Encoding
 `1TMC00AA AAAAAAAA VVVVVVVV (VVVVVVVV)`
@@ -83,8 +83,12 @@ If the condition is not met, all instructions until the appropriate conditional
 ### Code Type 0x2: End Conditional Block
 Code type 0x2 marks the end of a conditional block (started by Code Type 0x1 or Code Type 0x8).
 
+When an Else is executed, all instructions until the appropriate End conditional block terminator are skipped.
+
 #### Encoding
-`20000000`
+`2X000000`
+
++ X: End type (0 = End, 1 = Else).
 
 ---
 

stratosphere/dmnt/source/cheat/impl/dmnt_cheat_vm.cpp

@@ -387,8 +387,8 @@ namespace ams::dmnt::cheat::impl {
                 break;
             case CheatVmOpcodeType_EndConditionalBlock:
                 {
-                    /* 20000000 */
-                    /* There's actually nothing left to process here! */
+                    /* 2X000000 */
+                    opcode.end_cond.is_else = ((first_dword >> 28) & 0xF) == 1;
                 }
                 break;
             case CheatVmOpcodeType_ControlLoop:
@@ -668,7 +668,7 @@ namespace ams::dmnt::cheat::impl {
         return valid;
     }
 
-    void CheatVirtualMachine::SkipConditionalBlock() {
+    void CheatVirtualMachine::SkipConditionalBlock(bool is_if) {
         if (this->condition_depth > 0) {
             /* We want to continue until we're out of the current block. */
             const size_t desired_depth = this->condition_depth - 1;
@@ -685,15 +685,18 @@ namespace ams::dmnt::cheat::impl {
                 if (skip_opcode.begin_conditional_block) {
                     this->condition_depth++;
                 } else if (skip_opcode.opcode == CheatVmOpcodeType_EndConditionalBlock) {
-                    this->condition_depth--;
+                    if (!skip_opcode.end_cond.is_else) {
+                        this->condition_depth--;
+                    } else if (is_if && this->condition_depth - 1 == desired_depth) {
+                        /* An if will continue to an else at the same depth. */
+                        break;
+                    }
                 }
             }
         } else {
             /* Skipping, but this->condition_depth = 0. */
             /* This is an error condition. */
-            /* However, I don't actually believe it is possible for this to happen. */
-            /* I guess we'll throw a fatal error here, so as to encourage me to fix the VM */
-            /* in the event that someone triggers it? I don't know how you'd do that. */
+            /* This could occur with a mismatched "else" opcode, for example. */
             R_ABORT_UNLESS(ResultVirtualMachineInvalidConditionDepth());
         }
     }
@@ -850,15 +853,20 @@ namespace ams::dmnt::cheat::impl {
                         }
                         /* Skip conditional block if condition not met. */
                         if (!cond_met) {
-                            this->SkipConditionalBlock();
+                            this->SkipConditionalBlock(true);
                         }
                     }
                     break;
                 case CheatVmOpcodeType_EndConditionalBlock:
-                    /* Decrement the condition depth. */
-                    /* We will assume, graciously, that mismatched conditional block ends are a nop. */
-                    if (this->condition_depth > 0) {
-                        this->condition_depth--;
+                    if (cur_opcode.end_cond.is_else) {
+                        /* Skip to the end of the conditional block. */
+                        this->SkipConditionalBlock(false);
+                    } else {
+                        /* Decrement the condition depth. */
+                        /* We will assume, graciously, that mismatched conditional block ends are a nop. */
+                        if (this->condition_depth > 0) {
+                            this->condition_depth--;
+                        }
                     }
                     break;
                 case CheatVmOpcodeType_ControlLoop:
@@ -965,7 +973,7 @@ namespace ams::dmnt::cheat::impl {
                     /* Check for keypress. */
                     if ((cur_opcode.begin_keypress_cond.key_mask & kHeld) != cur_opcode.begin_keypress_cond.key_mask) {
                         /* Keys not pressed. Skip conditional block. */
-                        this->SkipConditionalBlock();
+                        this->SkipConditionalBlock(true);
                     }
                     break;
                 case CheatVmOpcodeType_PerformArithmeticRegister:
@@ -1164,7 +1172,7 @@ namespace ams::dmnt::cheat::impl {
 
                         /* Skip conditional block if condition not met. */
                         if (!cond_met) {
-                            this->SkipConditionalBlock();
+                            this->SkipConditionalBlock(true);
                         }
                     }
                     break;

stratosphere/dmnt/source/cheat/impl/dmnt_cheat_vm.hpp

@@ -142,7 +142,9 @@ namespace ams::dmnt::cheat::impl {
         VmInt value;
     };
 
-    struct EndConditionalOpcode {};
+    struct EndConditionalOpcode {
+        bool is_else;
+    };
 
     struct ControlLoopOpcode {
         bool start_loop;
@@ -286,7 +288,7 @@ namespace ams::dmnt::cheat::impl {
             size_t loop_tops[NumRegisters] = {0};
         private:
             bool DecodeNextOpcode(CheatVmOpcode *out);
-            void SkipConditionalBlock();
+            void SkipConditionalBlock(bool is_if);
             void ResetState();
 
             /* For implementing the DebugLog opcode. */