fix evaluation of expressions during first assembler pass

During the first assembler pass, the SymbolTable does not yet have all
symbols. During a symbol lookup the SymbolTable has so far returned a
fake symbol for non-existing symbols, to make the assembler happy
(values are not really being used during the first pass, so it's ok).

However now that expressions are supported, when the symbol lookup
encountered expressions during pass 1, it assumed those expressions were
"not-yet-existing-symbols", which is of course incorrect as they will
eventually be evaluated to integer values. Some opcodes were unhappy with
receiving an expression during pass 1 (e.g. the req_wr opcode, which
expects a sane address as a first argument).

This commit simply skips creating instructions during the first pass,
because all instructions are 32-bit (4 bytes) long anyway, so the content
doesn't matter during that first assembler pass, which only measures
section sizes.

Author: wnienhaus

esp32_ulp/assemble.py

@@ -277,7 +277,7 @@ def assembler_pass(self, lines):
                     # machine instruction
                     func = getattr(opcodes, 'i_' + opcode.lower(), None)
                     if func is not None:
-                        instruction = func(*args)
+                        instruction = 0 if self.a_pass == 1 else func(*args)
                         self.append_section(instruction.to_bytes(4, 'little'), TEXT)
                         continue
                 raise ValueError('Unknown opcode or directive: %s' % opcode)

tests/assemble.py

@@ -175,6 +175,19 @@ def test_assemble_optional_comment_removal():
     assert raised
 
 
+def test_assemble_test_regressions_from_evaluation():
+    line = " reg_wr (0x3ff48400 + 0x10), 1, 1, 1"
+
+    a = Assembler()
+    raised = False
+    try:
+        a.assemble(line)
+    except ValueError as e:
+        if str(e) == 'invalid register base':  # ensure we trapped the expected Exception
+            raised = True
+    assert not raised
+
+
 def test_symbols():
     st = SymbolTable({}, {}, {})
     for entry in [
@@ -237,4 +250,5 @@ def test_symbols():
 test_assemble_uppercase_opcode()
 test_assemble_evalulate_expressions()
 test_assemble_optional_comment_removal()
+test_assemble_test_regressions_from_evaluation()
 test_symbols()