> From:   "PhiHo Hoang" < phiho.hoang at r... >
> Date:   Sun Jul 20, 2003  7:44 pm
> Subject:   Re: non-inlined VM.
>
>
>
> Hi John.
>
> Thanks for the stats.
>
> What would you suggest for a compromised speed/size
> optimisation (taking into account the sizes of the routines) ?
>
> Cheers,
>
> PhiHo.
>


For interest sake, I looked a bit more into this. Just by doing post  
processing on the C code I noticed that
case 7:
			/* pushReceiverVariableBytecode */
			{
				fetchNextBytecode();
				pushReceiverVariable(7 & 15);
			}

000000D8: 48000001  bl         .fetchNextBytecode
000000DC: 38600007  li         r3,7
000000E0: 48000001  bl         .pushReceiverVariable

which really is...

000000D4: 48000001  bl         .fetchNextBytecode

00000000: 7C0802A6  mflr       r0        /*  fetchNextBytecode */
00000004: 90010008  stw        r0,8(SP)
00000008: 9421FFC0  stwu       SP,-64(SP)
0000000C: 48000001  bl         .fetchByte

00000000: 80620000  lwz        r3,foo(RTOC) /* fetchByte */
00000004: 80830000  lwz        r4,0(r3)
00000008: 8064011C  lwz        r3,284(r4)
0000000C: 38630001  addi       r3,r3,1
00000010: 9064011C  stw        r3,284(r4)
00000014: 88630000  lbz        r3,0(r3)
00000018: 4E800020  blr


00000010: 80820000  lwz        r4,foo(RTOC) /*  fetchNextBytecode */
00000014: 80840000  lwz        r4,0(r4)
00000018: 90640034  stw        r3,52(r4)
0000001C: 80010048  lwz        r0,72(SP)
00000020: 38210040  addi       SP,SP,64
00000024: 7C0803A6  mtlr       r0
00000028: 4E800020  blr


000000D8: 38600007  li         r3,7
000000DC: 48000001  bl         .pushReceiverVariable


can be altered to this, because that is what the fetchNextBytecode  
really does...

		case 7:
			/* pushReceiverVariableBytecode */
			{
				foo->currentBytecode = byteAt(++foo->localIP)
				pushReceiverVariable(7 & 15);
			}

0000015C: 809F011C  lwz        r4,284(r31)
00000160: 38600007  li         r3,7
00000164: 38840001  addi       r4,r4,1
00000168: 909F011C  stw        r4,284(r31)
0000016C: 88040000  lbz        r0,0(r4)
00000170: 901F0034  stw        r0,52(r31)
00000174: 48000001  bl         .pushReceiverVariable


21 instructions, versus 7. A bit more work if you wanted to turn all  
foo->localIP to just localIP, but nothing a post bit of string  
manipulation could not do...

Also consider dragging in the
int externalizeIPandSP(void) {
register struct foo * foo = &fum;
	foo->instructionPointer = ((int) foo->localIP);
	foo->stackPointer = ((int) foo->localSP);
	foo->theHomeContext = foo->localHomeContext;
}
  and altering the references to localSP and localHomeContext.
Again I think a simple task, that would get you lots of improvement.

--
======================================================================== 
===
John M. McIntosh <johnmci at smalltalkconsulting.com> 1-800-477-2659
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
======================================================================== 
===