VirtualMachine: Do not use function calls for loops

Author: adazem009

src/engine/virtualmachine.cpp

@@ -36,6 +36,7 @@ VirtualMachine::VirtualMachine(Target *target, Engine *engine) :
     m_regs = new Value *[MAX_REG_COUNT];
     for (int i = 0; i < MAX_REG_COUNT; i++)
         m_regs[i] = new Value();
+    m_loops.reserve(256);
 }
 
 /*! Destroys the VirtualMachine object. */
@@ -192,35 +193,54 @@ unsigned int *VirtualMachine::run(unsigned int *pos)
         loopEnd = pos;
         while (*loopEnd != OP_LOOP_END)
             loopEnd += instruction_arg_count[*loopEnd++];
+        pos = loopEnd;
     } else {
-        for (size_t i = 0; i < loopCount; i++)
-            loopEnd = run(pos);
+        Loop l;
+        l.isRepeatLoop = true;
+        l.start = pos;
+        l.index = 0;
+        l.max = loopCount;
+        m_loops.push_back(l);
     }
-    pos = loopEnd;
     DISPATCH();
 
 do_until_loop:
     loopStart = run(pos);
     if (!READ_LAST_REG()->toBool()) {
-        do {
-            FREE_REGS(1);
-            loopEnd = run(loopStart);
-            run(pos);
-        } while (!READ_LAST_REG()->toBool());
-        FREE_REGS(1);
+        Loop l;
+        l.isRepeatLoop = false;
+        l.start = pos;
+        m_loops.push_back(l);
+        pos = loopStart;
     } else {
-        loopEnd = loopStart;
-        while (*loopEnd != OP_LOOP_END)
-            loopEnd += instruction_arg_count[*loopEnd++];
+        pos = loopStart;
+        while (*pos != OP_LOOP_END)
+            pos += instruction_arg_count[*pos++];
     }
-    pos = loopEnd;
+    FREE_REGS(1);
     DISPATCH();
 
 do_begin_until_loop:
     return pos;
 
-do_loop_end:
-    return pos;
+do_loop_end : {
+    Loop &l = m_loops.back();
+    if (l.isRepeatLoop) {
+        if (++l.index < l.max)
+            pos = l.start;
+        else
+            m_loops.pop_back();
+        DISPATCH();
+    } else {
+        loopStart = run(l.start);
+        if (!READ_LAST_REG()->toBool())
+            pos = loopStart;
+        else
+            m_loops.pop_back();
+        FREE_REGS(1);
+        DISPATCH();
+    }
+}
 
 do_print:
     std::cout << READ_LAST_REG()->toString() << std::endl;

src/engine/virtualmachine.h

@@ -114,12 +114,20 @@ class LIBSCRATCHCPP_EXPORT VirtualMachine
             0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1
         };
 
+        typedef struct
+        {
+                bool isRepeatLoop;
+                unsigned int *start;
+                size_t index, max;
+        } Loop;
+
         unsigned int *m_bytecode;
         std::vector<unsigned int> m_bytecodeVector;
 
         Target *m_target = nullptr;
         Engine *m_engine = nullptr;
         bool m_atEnd = false;
+        std::vector<Loop> m_loops;
 
         BlockFunc *m_functions;
         std::vector<BlockFunc> m_functionsVector;