Avoid optimizing primitive #33 in vm.c (for VC++)

[Lendvai Attila]

hi!

Please find the disassembly below of the optimized/non-optimized
version. I've tried to surround the signed cast with an extra (), but
the same result

static INLINE signed long int ObjectPointer_asSmallInt(ObjectPointer
oop)
{
  return ((signed long int) oop) >> 1;
}

in the optimized version the rotation is done with an "shr" opcode,
which clears the MSB. in the non-optimized version, "sar" is used, which
behaves as expected...

there are other >> 1 operations all around in vm.c, but still turning
off global optimizations with the #pragma results in a working vm.

I'm downloading VC++ 2005 beta now and see what's in there?

- 101

MSDN jokes, the search itself:
http://search.microsoft.com/search/results.aspx?view=msdn&st=a&na=81&qu=
&qp=global+optimizations&qa=&qn=&c=10&s=1
some intresting pieces:
http://support.microsoft.com/default.aspx?scid=kb;en-us;250887
http://support.microsoft.com/default.aspx?scid=kb;en-us;113427



NON-OPTIMIZED:

void _primitive33(struct Interpreter * interpreter, ObjectPointer *
arguments, unsigned long int argumentsSize, struct OopArray * optionals)
{
00408B50  push        ebp  
00408B51  mov         ebp,esp 
00408B53  sub         esp,18h 
  ObjectPointer x;
  ObjectPointer y;

  x = arguments[0];
00408B56  mov         eax,dword ptr [arguments] 
00408B59  mov         ecx,dword ptr [eax] 
00408B5B  mov         dword ptr [x],ecx 
  y = arguments[1];
00408B5E  mov         edx,dword ptr [arguments] 
00408B61  mov         eax,dword ptr [edx+4] 
00408B64  mov         dword ptr [y],eax 
  PSInterpreter_stackPush_(interpreter, ObjectPointer_asSmallInt(x) <
ObjectPointer_asSmallInt(y)?CurrentMemory->TrueObject:CurrentMemory->Fal
seObject);
00408B67  mov         ecx,dword ptr [x] 
00408B6A  sar         ecx,1 
00408B6C  mov         edx,dword ptr [y] 
00408B6F  sar         edx,1 
00408B71  cmp         ecx,edx 
00408B73  jge         _primitive33+32h (408B82h) 
00408B75  mov         eax,dword ptr [_CurrentMemory (411D60h)] 
00408B7A  mov         ecx,dword ptr [eax+24h] 
00408B7D  mov         dword ptr [ebp-18h],ecx 
00408B80  jmp         _primitive33+3Eh (408B8Eh) 
00408B82  mov         edx,dword ptr [_CurrentMemory (411D60h)] 
00408B88  mov         eax,dword ptr [edx+28h] 
00408B8B  mov         dword ptr [ebp-18h],eax 
00408B8E  mov         ecx,dword ptr [ebp-18h] 
00408B91  push        ecx  
00408B92  mov         edx,dword ptr [interpreter] 
00408B95  push        edx  
00408B96  call        PSInterpreter_stackPush_ (406860h) 
00408B9B  add         esp,8 
}
00408B9E  mov         esp,ebp 
00408BA0  pop         ebp  
00408BA1  ret              




OPTIMIZED:

void _primitive33(struct Interpreter * interpreter, ObjectPointer *
arguments, unsigned long int argumentsSize, struct OopArray * optionals)
{
  ObjectPointer x;
  ObjectPointer y;

  x = arguments[0];
  y = arguments[1];
  PSInterpreter_stackPush_(interpreter, ObjectPointer_asSmallInt(x) <
ObjectPointer_asSmallInt(y)?CurrentMemory->TrueObject:CurrentMemory->Fal
seObject);
004064E0  mov         eax,dword ptr [esp+8] 
004064E4  mov         ecx,dword ptr [eax+4] 
004064E7  mov         edx,dword ptr [eax] 
004064E9  shr         ecx,1 
004064EB  shr         edx,1 
004064ED  cmp         edx,ecx 
004064EF  push        esi  
004064F0  push        edi  
004064F1  jge         _primitive33+1Dh (4064FDh) 
004064F3  mov         eax,dword ptr [_CurrentMemory (40FD60h)] 
004064F8  mov         edi,dword ptr [eax+24h] 
004064FB  jmp         _primitive33+26h (406506h) 
004064FD  mov         ecx,dword ptr [_CurrentMemory (40FD60h)] 
00406503  mov         edi,dword ptr [ecx+28h] 
00406506  mov         esi,dword ptr [esp+0Ch] 
0040650A  mov         edx,dword ptr [esi+24h] 
0040650D  cmp         edx,dword ptr [esi+28h] 
00406510  jne         _primitive33+3Bh (40651Bh) 
00406512  push        esi  
00406513  call        PSInterpreter_growStack (404D60h) 
00406518  add         esp,4 
0040651B  mov         eax,dword ptr [esi+24h] 
0040651E  mov         ecx,dword ptr [esi+0Ch] 
00406521  mov         dword ptr [ecx+eax*4+0Ch],edi 
00406525  add         dword ptr [esi+24h],1 
00406529  pop         edi  
0040652A  pop         esi  
}
0040652B  ret              




:: -----Original Message-----
:: From: slate-bounces at tunes.org 
:: [mailto:slate-bounces at tunes.org] On Behalf Of Lee Salzman
:: Sent: Monday, August 09, 2004 9:01 AM
:: To: Paul Dufresne
:: Cc: slate at tunes.org
:: Subject: Re: Avoid optimizing primitive #33 in vm.c (for VC++)
:: 
:: 
:: The primitive causing the problem is SmallInteger < 
:: SmallInteger, not the Float one. Not sure why VC would do 
:: this, though, other than that it 
:: may just be a silly VC bug. Anyone has any ideas?
:: 
:: Lee
:: 
:: On Mon, Aug 09, 2004 at 06:11:45AM +0000, Paul Dufresne wrote:
:: > I said: "I think primitive 13 is this one:"
:: > but really meant primitive 33.
:: > 
:: > Also, somehow I find it strange myself that the
:: > primitive causing problem be < for Floats,
:: > so it would be nice for someone to confirm.
:: > 
:: > Finally, building bootstrap image have been done without a hitch. 
:: > (Just hope the expression 'without a hitch' is Ok in english).
:: > 
:: > --Paul
:: > 
:: 
::