[Bug java/23500] New: Optimization: Skip _Jv_InitClass for intra-class static method calls

[greenrd at greenrd dot org]

Java requires a class initialization check when any public static method is
called. But when we are calling from another method in the _same_ class, we
already know that the class has been initialized, so we can optimize away the
call to _Jv_InitClass, even if we're not inlining. Here's how:

Reorder the call, so that this (on x86):

.globl _ZN4Test10assertHackEb
        .type   _ZN4Test10assertHackEb, @function
_ZN4Test10assertHackEb:
.LFB5:
        .file 1 "Test.java"
        .loc 1 43 0
.LVL0:
        pushl   %ebp
.LCFI0:
        movl    %esp, %ebp
.LCFI1:
        pushl   %ebx
.LCFI2:
        subl    $16, %esp
.LCFI3:
        movb    8(%ebp), %bl
        .loc 1 43 0
        pushl   $_ZN4Test6class$E
.LCFI4:
        call    _Jv_InitClass


becomes something like this:

.globl _ZN4Test10assertHackEb
        .type   _ZN4Test10assertHackEb, @function
_ZN4Test10assertHackEb:
.LFB5:
        .file 1 "Test.java"
        .loc 1 43 0
        pushl   $_ZN4Test6class$E
.LCFI4:
        call    _Jv_InitClass
.LVL0:
        pushl   %ebp
.LCFI0:
        movl    %esp, %ebp
.LCFI1:
        pushl   %ebx
.LCFI2:
        subl    $16, %esp
.LCFI3:
        movb    8(%ebp), %bl

and intra-class method calls to that method, call to .LVL0 instead of
_ZN4Test10assertHackEb.

-- 
           Summary: Optimization: Skip _Jv_InitClass for intra-class static
                    method calls
           Product: gcc
           Version: 4.0.2
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: java
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: greenrd at greenrd dot org
                CC: gcc-bugs at gcc dot gnu dot org,java-prs at gcc dot gnu
                    dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23500