On Wed, 8 Aug 2001, Thiemo Seufer wrote:
> Ralf Baechle wrote:
> > On Wed, Aug 08, 2001 at 11:02:44AM -0400, J. Scott Kasten wrote:
> >
> > > gcc -mips3 -mint64 test.c -o test
> > >
> > > The file command says:
> > >
> > > test: ELF N32 MSB mips-3 dynamic executable (not stripped) MIPS - version 1
> ^^^
> I don't know how file detects this, but at least current CVS gas
> does not set the appropriate flag in the object file header.
Gas does not apply here. We're talking about gcc running under Irix with
the native as and ld tools. I'm using gcc-2.91.66 (egcs-1.1.2),
gcc-2.95.2, MipsPro 7.30 as and ld.
> > >
> > > Run:
> > >
> > > sizeof(int) = 8, sizeof(*) = 8
> ^ ^
> This should be both 4, I assume this happened due to -mint64.
Not totally. -mips3 generates values of 4 and 8. The -mint64 takes it to
8 and 8. If I just invoke gcc with no -m flags, it does produce 4 and 4.
> > > If we look at the assembly, we see a sign extended 64 bit load, and a 64
> > > bit add. So we are indeed generating 64 bit instructions, at least in
> > > some cases.
> > >
> > > dli $3,0xa # 10
>
> To what does this dli get expanded? I'm interested in the output of
> objdump -d.
test.S
sd $2,40($fp)
ld $2,40($fp)
dli $3,0xa # 10
sd $3,0($2)
ld $2,32($fp)
daddu $3,$2,1
sd $3,32($fp)
ld $2,40($fp)
objdump -d
100012b0: ffc20028 sd $v0,40($s8)
100012b4: dfc20028 ld $v0,40($s8)
100012b8: 2403000a li $v1,10
100012bc: fc430000 sd $v1,0($v0)
100012c0: dfc20020 ld $v0,32($s8)
100012c4: 64430001 daddiu $v1,$v0,1
100012c8: ffc30020 sd $v1,32($s8)
100012cc: dfc20028 ld $v0,40($s8)
Just for kicks, instead of *j = 10, which is trivial, I picked a true 64
bit constant:
sd $2,40($fp)
ld $2,40($fp)
dli $3,0x807060504030201
sd $3,0($2)
ld $2,32($fp)
daddu $3,$2,1
sd $3,32($fp)
ld $2,40($fp)
100012b0: ffc20028 sd $v0,40($s8)
100012b4: dfc20028 ld $v0,40($s8)
100012b8: 3c030807 lui $v1,0x807
100012bc: 34630605 ori $v1,$v1,0x605
100012c0: 00031c38 dsll $v1,$v1,0x10
100012c4: 34630403 ori $v1,$v1,0x403
100012c8: 00031c38 dsll $v1,$v1,0x10
100012cc: 34630201 ori $v1,$v1,0x201
100012d0: fc430000 sd $v1,0($v0)
100012d4: dfc20020 ld $v0,32($s8)
100012d8: 64430001 daddiu $v1,$v0,1
100012dc: ffc30020 sd $v1,32($s8)
100012e0: dfc20028 ld $v0,40($s8)
Ouch that's a painfull load. It's interesting that in both cases, it
effectively makes the constant load a 16 bit operation, does the math 64
bit, and stores 64 bit.
