refact: do not emit LBound tables for statically accessed arrays

Author: boriel

src/arch/z80/visitor/function_translator.py

@@ -61,15 +61,16 @@ def visit_FUNCTION(self, node):
             if local_var.class_ == CLASS.array and local_var.scope == SCOPE.local:
                 lbound_label = local_var.mangled + ".__LBOUND__"
                 ubound_label = local_var.mangled + ".__UBOUND__"
+                lbound_needed = not local_var.is_zero_based and local_var.is_dynamically_accessed
 
-                bound_ptrs = ["0" if local_var.is_zero_based else lbound_label, "0"]
+                bound_ptrs = [lbound_label if lbound_needed else "0", "0"]
                 if local_var.ubound_used:
                     bound_ptrs[1] = ubound_label
 
                 if bound_ptrs != ["0", "0"]:
                     OPTIONS["__DEFINES"].value["__ZXB_USE_LOCAL_ARRAY_WITH_BOUNDS__"] = ""
 
-                if not local_var.is_zero_based:
+                if lbound_needed:
                     l = ["%04X" % bound.lower for bound in local_var.bounds]
                     bound_tables.append(LabelledData(lbound_label, l))
 

src/arch/z80/visitor/var_translator.py

@@ -48,7 +48,7 @@ def visit_ARRAYDECL(self, node):
         ubound_label = entry.mangled + ".__UBOUND__"
         bound_ptrs = ["0", "0"]  # NULL by default
 
-        if not entry.is_zero_based:
+        if not entry.is_zero_based and entry.is_dynamically_accessed:
             bound_ptrs[0] = lbound_label
 
         if entry.ubound_used or OPTIONS.array_check:

src/lib/arch/zx48k/runtime/bound.asm

@@ -70,6 +70,10 @@ __CONT:
     ld h, (hl)
     ld l, a         ; LD HL, (HL) => Origin of L/U Bound table
 
+    ; for LBound only, HL = 0x0000 (NULL) if the array is all 0-based
+    or h
+    ret z           ; Should never happen for UBound
+
     add hl, de      ; hl += OFFSET __LBOUND._xxxx
     ld e, (hl)      ; de = (hl)
     inc hl

src/symbols/arrayaccess.py

@@ -35,6 +35,7 @@ class SymbolARRAYACCESS(SymbolCALL):
     def __init__(self, entry, arglist: SymbolARGLIST, lineno: int, filename: str):
         super().__init__(entry, arglist, lineno, filename)
         assert all(gl.BOUND_TYPE == x.type_.type_ for x in arglist), "Invalid type for array index"
+        self.entry.ref.is_dynamically_accessed = True
 
     @property
     def entry(self):
@@ -90,6 +91,12 @@ def offset(self) -> int | None:
         offset *= self.type_.size
         return offset
 
+    @cached_property
+    def is_constant(self) -> bool:
+        """Whether this array access is constant.
+        e.g. A(1) is constant. A(i) is not."""
+        return self.offset is None
+
     @classmethod
     def make_node(cls, id_: str, arglist: SymbolARGLIST, lineno: int, filename: str) -> Optional["SymbolARRAYACCESS"]:
         """Creates an array access. A(x1, x2, ..., xn)"""

src/symbols/id_/ref/arrayref.py

@@ -8,7 +8,7 @@
 
 
 class ArrayRef(VarRef):
-    __slots__ = "lbound_used", "ubound_used"
+    __slots__ = "is_dynamically_accessed", "lbound_used", "ubound_used"
 
     def __init__(self, parent: SymbolID, bounds: SymbolBOUNDLIST):
         super().__init__(parent)
@@ -19,6 +19,7 @@ def __init__(self, parent: SymbolID, bounds: SymbolBOUNDLIST):
         self.callable = True
         self.offset: str | None = None
         self.byref = False  # Whether this array is passed by ref to a func
+        self.is_dynamically_accessed: bool = False  # Whether the array is accessed using variables at any moment
 
     @property
     def token(self) -> str: