Fix decoding for register ops; add test

Author: gvanrossum

Tools/cases_generator/generate_cases.py

@@ -240,9 +240,11 @@ def __init__(self, inst: parser.InstDef, a: "Analyzer"):
                 break
         self.unmoved_names = frozenset(unmoved_names)
         if self.register:
-            num_regs = len(self.input_effects) + len(self.output_effects)
-            num_dummies = (num_regs // 2) * 2 + 1 - num_regs
-            fmt = "I" + "B"*num_regs + "X"*num_dummies
+            fmt = "I"
+            for effect in self.input_effects + self.output_effects:
+                fmt += "X" if effect.name == UNUSED else "B"
+            if len(fmt) % 2 != 0:
+                fmt += "X"
         else:
             if variable_used(inst, "oparg"):
                 fmt = "IB"
@@ -262,7 +264,7 @@ def __init__(self, inst: parser.InstDef, a: "Analyzer"):
         self.instr_fmt = fmt
 
     def analyze_registers(self, a: "Analyzer") -> None:
-        regs = iter(("REG(oparg1)", "REG(oparg2)", "REG(oparg3)"))
+        regs = iter(("REG(oparg)", "REG(oparg2)", "REG(oparg3)"))
         try:
             self.input_registers = [
                 next(regs) for ieff in self.input_effects if ieff.name != UNUSED

Tools/cases_generator/test_generator.py

@@ -512,3 +512,42 @@ def test_extended_cases():
         }
     """
     run_cases_test(input, output)
+
+def test_long_register():
+    input = """
+        register inst(OP1, (left, right -- result)) {
+            result = spam(left, right);
+        }
+        register inst(OP2, (left, unused -- result)) {
+            result = spam(left, NULL);
+        }
+    """
+    output = """
+        TARGET(OP1) {
+            // Decode rest of instruction
+            oparg2 = next_instr[0].opcode;
+            oparg3 = next_instr[0].oparg;
+            frame->prev_instr = next_instr++;
+        into_op1:;  // For EXTENDED_ARG_3
+            PyObject *left = REG(oparg);
+            PyObject *right = REG(oparg2);
+            PyObject *result;
+            result = spam(left, right);
+            Py_XSETREF(REG(oparg3), result);
+            DISPATCH();
+        }
+
+        TARGET(OP2) {
+            // Decode rest of instruction
+            // (oparg2 is unused)
+            oparg3 = next_instr[0].oparg;
+            frame->prev_instr = next_instr++;
+        into_op2:;  // For EXTENDED_ARG_3
+            PyObject *left = REG(oparg);
+            PyObject *result;
+            result = spam(left, NULL);
+            Py_XSETREF(REG(oparg2), result);
+            DISPATCH();
+        }
+    """
+    run_cases_test(input, output)