[GROOVY-7659] primopts for CompileStatic integer division

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.4.5
• Component/s: primtive opts, Static compilation
• Assignee: Unassigned
• Reporter: Jason Winnebeck
• Created: 03/Nov/15 15:56
• Updated: 20/Jan/16 18:42

Description

Since operations a+b with int can be supported with primitive operations, it would be nice if division could as well. I think this is possible to do in certain circumstances and still adhere to the semantics that int / int results in BigDecimal. I believe if you have (int)(int / int), I can't think of a case where a primitive division would give a different result than with BigDecimal.

@groovy.transform.CompileStatic
int idiv_static(int a) {
  (int)(a / 2)
}

int idiv_dynamic(int a) {
  (int)(a / 2)
}

@groovy.transform.CompileStatic
int iplus_static(int a) {
  a + 5
}

int iplus_dynamic(int a) {
  a + 5
}

We can see the bytecode for iplus_static generated by Groovy 2.4.5:

ILOAD 1
ICONST_5
IADD
IRETURN

But for idiv_static, it converts the ints to Integer, calls a method that results in BigDecimal division and then converts that to int.

    ILOAD 1
    INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer;
    ICONST_2
    INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer;
    INVOKESTATIC org/codehaus/groovy/runtime/dgmimpl/NumberNumberDiv.div (Ljava/lang/Number;Ljava/lang/Number;)Ljava/lang/Number;
    INVOKESTATIC org/codehaus/groovy/runtime/typehandling/DefaultTypeTransformation.intUnbox (Ljava/lang/Object;)I
    IRETURN