refactoring for issue #5

source/m3_compile.c

@@ -48,7 +48,7 @@ u32 GetTypeNumSlots (u8 i_type)
 }
 
 i16  GetStackTopIndex  (IM3Compilation o)
-{
+{                                                           d_m3Assert (o->stackIndex > 0);
     return o->stackIndex - 1;
 }
 
@@ -100,13 +100,19 @@ i16  GetNumBlockValues  (IM3Compilation o)
 }
 
 
+bool IsStackIndexInRegister  (IM3Compilation o, u16 i_stackIndex)
+{                                                                           d_m3Assert (i_stackIndex < o->stackIndex);
+    return (o->wasmStack [i_stackIndex] >= d_m3Reg0SlotAlias);
+}
+
+
 bool  IsStackTopInRegister  (IM3Compilation o)
 {
-    i16 i = GetStackTopIndex (o);               d_m3Assert (i >= 0 or IsStackPolymorphic (o));
+    i16 i = GetStackTopIndex (o);                                           d_m3Assert (i >= 0 or IsStackPolymorphic (o));
 
     if (i >= 0)
     {
-        return (o->wasmStack [i] >= d_m3Reg0SlotAlias);
+        return IsStackIndexInRegister (o, (u16) i);
     }
     else return false;
 }
@@ -143,7 +149,7 @@ bool  IsStackTopMinus1InRegister  (IM3Compilation o)
 {
     i16 i = GetStackTopIndex (o);
 
-    if (i > 0)
+    if (i >= 1)
     {
         return (o->wasmStack [i - 1] >= d_m3Reg0SlotAlias);
     }
@@ -570,15 +576,16 @@ bool  PatchBranches  (IM3Compilation o)
 //-------------------------------------------------------------------------------------------------------------------------
 
 
-M3Result CopyTopSlot (IM3Compilation o, u16 i_destSlot)
+M3Result CopyStackSlot (IM3Compilation o, u16 i_stackIndex, u16 i_destSlot)
 {
     M3Result result = m3Err_none;
 
     IM3Operation op;
 
-    u8 type = GetStackTopType (o);
+    u8 type = GetStackBottomType (o, i_stackIndex);
+    bool inRegister = IsStackIndexInRegister (o, i_stackIndex);
 
-    if (IsStackTopInRegister (o))
+    if (inRegister)
     {
         op = c_setSetOps [type];
     }
@@ -587,13 +594,24 @@ M3Result CopyTopSlot (IM3Compilation o, u16 i_destSlot)
 _   (EmitOp (o, op));
     EmitSlotOffset (o, i_destSlot);
 
-    if (IsStackTopInSlot (o))
-        EmitSlotOffset (o, GetStackTopSlotIndex (o));
+    if (not inRegister)
+        EmitSlotOffset (o, o->wasmStack [i_stackIndex]);
 
     _catch: return result;
 }
 
 
+M3Result CopyTopSlot (IM3Compilation o, u16 i_destSlot)
+{
+    M3Result result;
+
+    i16 stackTop = GetStackTopIndex (o);
+_   (CopyStackSlot (o, (u16) stackTop, i_destSlot));
+    
+    _catch: return result;
+}
+
+
 // a copy-on-write strategy is used with locals. when a get local occurs, it's not copied anywhere. the stack
 // entry just has a index pointer to that local memory slot.
 // then, when a previously referenced local is set, the current value needs to be preserved for those references