Date: Tue, 9 Mar 2010 21:27:54 +1100 From: Peter Jeremy <peterjeremy@acm.org> To: freebsd-sparc64@freebsd.org Cc: Marius Strobl <marius@alchemy.franken.de> Subject: Re: gcc code generation problems Message-ID: <20100309102753.GC3978@server.vk2pj.dyndns.org> In-Reply-To: <20100308190301.GA69938@server.vk2pj.dyndns.org> References: <20100228192329.GA68252@server.vk2pj.dyndns.org> <20100308190301.GA69938@server.vk2pj.dyndns.org>
next in thread | previous in thread | raw e-mail | index | archive | help
--5QAgd0e35j3NYeGe
Content-Type: multipart/mixed; boundary="hQiwHBbRI9kgIhsi"
Content-Disposition: inline
--hQiwHBbRI9kgIhsi
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
On 2010-Mar-09 06:03:01 +1100, Peter Jeremy <peterjeremy@acm.org> wrote:
>code works. The "UltraSPARC IIIi Processor User's Manual", indicates
>that fxtod will trap for operands >=3D 2^51 (fdtox will trap for
>operands >=3D 2^53 and is therefore executed in hardware) which seems to
>point the finger at the FP emulation code in the userland trap handler.
Attached is a block of assembler that loads all 32 double FP registers
with known non-zero values, executes a fxtod and then prints the
values of all FP registers. This shows that the register following
the emulated fxtod target is incorrectly zeroed. In the attached, the
target is %f10 but I've also tried %f8 - which zeroed %f10. The three
columns are: FP register number, value before fxtod, value after fxtod.
Typical output on my USIIIi:
0 0xfddb757dbd5b7ddf 0xfddb757dbd5b7ddf
2 0xfbb6eafb7ab6fbbf 0xfbb6eafb7ab6fbbf
4 0xf76dd5f6f56df77f 0xf76dd5f6f56df77f
6 0xeedbabedeadbeeff 0xeedbabedeadbeeff
8 0xddb757dbd5b7ddff 0xddb757dbd5b7ddff
10 0xbb6eafb7ab6fbbff 0x432ffffffffffffe
12 0x76dd5f6f56df77ff 0x0000000000000000
14 0x000fffffffffffff 0x000fffffffffffff
16 0xdb757dbd5b7ddffd 0xdb757dbd5b7ddffd
18 0xb6eafb7ab6fbbffb 0xb6eafb7ab6fbbffb
20 0x6dd5f6f56df77ff7 0x6dd5f6f56df77ff7
22 0xdbabedeadbeeffee 0xdbabedeadbeeffee
24 0xb757dbd5b7ddffdd 0xb757dbd5b7ddffdd
26 0x6eafb7ab6fbbffbb 0x6eafb7ab6fbbffbb
28 0xdd5f6f56df77ff76 0xdd5f6f56df77ff76
30 0xbabedeadbeeffeed 0xbabedeadbeeffeed
32 0x757dbd5b7ddffddb 0x757dbd5b7ddffddb
34 0xeafb7ab6fbbffbb6 0xeafb7ab6fbbffbb6
36 0xd5f6f56df77ff76d 0xd5f6f56df77ff76d
38 0xabedeadbeeffeedb 0xabedeadbeeffeedb
40 0x57dbd5b7ddffddb7 0x57dbd5b7ddffddb7
42 0xafb7ab6fbbffbb6e 0xafb7ab6fbbffbb6e
44 0x5f6f56df77ff76dd 0x5f6f56df77ff76dd
46 0xbedeadbeeffeedba 0xbedeadbeeffeedba
48 0x7dbd5b7ddffddb75 0x7dbd5b7ddffddb75
50 0xfb7ab6fbbffbb6ea 0xfb7ab6fbbffbb6ea
52 0xf6f56df77ff76dd5 0xf6f56df77ff76dd5
54 0xedeadbeeffeedbab 0xedeadbeeffeedbab
56 0xdbd5b7ddffddb757 0xdbd5b7ddffddb757
58 0xb7ab6fbbffbb6eaf 0xb7ab6fbbffbb6eaf
60 0x6f56df77ff76dd5f 0x6f56df77ff76dd5f
62 0xdeadbeeffeedbabe 0xdeadbeeffeedbabe
>I am still looking into the emulation code.
I haven't found the above bug yet but I have found two other bugs in
the FP register decoding in __fpu_execute().
Firstly, for fxto{s,d,q} decoding, rs2 is set generically using
RN_DECODE() with 'type' =3D=3D 0 (because the low 2 bits are always 0. In
this case, RN_DECODE() will assume a 32-bit rs2, whereas the SPARC
architecture manual specifies that fxto{s,d,q} has a 64-bit rs2.
The effect is that using a source register in the upper half will
alias to the lower half.
The rd value used in f{s,d,q}tox suffers from the same problem.
--=20
Peter Jeremy
--hQiwHBbRI9kgIhsi
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment; filename="eval.s"
Content-Transfer-Encoding: quoted-printable
.file "eval.s"
.section ".text"
.macro initfp ireg,wreg,wmem,fnum
stx \ireg,\wmem
ldd \wmem,%f\fnum
sllx \ireg,1,\wreg
srlx \ireg,63,\ireg
or \ireg,\wreg,\ireg
.endm
.macro savefp wmem,fnum
std %f\fnum,[\wmem+4*\fnum]
.endm
.align 32
.global main
.type main, #function
.proc 04
main:
.register %g2, #scratch
.register %g3, #scratch
save %sp, -224, %sp
! Initialise all FP registers
setx 0xfeedbabedeadbeef,%g1,%g2
setx foo,%g1,%l2
setx bar,%g1,%l3
stx %g2,[%l2]
ldd [%l2],%f0
sllx %g2,1,%g1
srlx %g2,63,%g2
or %g2,%g1,%g2
initfp %g2,%g1,[%l2],0
initfp %g2,%g1,[%l2],2
initfp %g2,%g1,[%l2],4
initfp %g2,%g1,[%l2],6
initfp %g2,%g1,[%l2],8
initfp %g2,%g1,[%l2],10
initfp %g2,%g1,[%l2],12
initfp %g2,%g1,[%l2],14
initfp %g2,%g1,[%l2],16
initfp %g2,%g1,[%l2],18
initfp %g2,%g1,[%l2],20
initfp %g2,%g1,[%l2],22
initfp %g2,%g1,[%l2],24
initfp %g2,%g1,[%l2],26
initfp %g2,%g1,[%l2],28
initfp %g2,%g1,[%l2],30
initfp %g2,%g1,[%l2],32
initfp %g2,%g1,[%l2],34
initfp %g2,%g1,[%l2],36
initfp %g2,%g1,[%l2],38
initfp %g2,%g1,[%l2],40
initfp %g2,%g1,[%l2],42
initfp %g2,%g1,[%l2],44
initfp %g2,%g1,[%l2],46
initfp %g2,%g1,[%l2],48
initfp %g2,%g1,[%l2],50
initfp %g2,%g1,[%l2],52
initfp %g2,%g1,[%l2],54
initfp %g2,%g1,[%l2],56
initfp %g2,%g1,[%l2],58
initfp %g2,%g1,[%l2],60
initfp %g2,%g1,[%l2],62
mov 1,%g2
sllx %g2,52,%g2
dec %g2
stx %g2,[%l2]
!!! Initialise fxtod source with wanted value
ldd [%l2],%f14
! Save FP regs to memory
savefp %l2,0
savefp %l2,2
savefp %l2,4
savefp %l2,6
savefp %l2,8
savefp %l2,10
savefp %l2,12
savefp %l2,14
savefp %l2,16
savefp %l2,18
savefp %l2,20
savefp %l2,22
savefp %l2,24
savefp %l2,26
savefp %l2,28
savefp %l2,30
savefp %l2,32
savefp %l2,34
savefp %l2,36
savefp %l2,38
savefp %l2,40
savefp %l2,42
savefp %l2,44
savefp %l2,46
savefp %l2,48
savefp %l2,50
savefp %l2,52
savefp %l2,54
savefp %l2,56
savefp %l2,58
savefp %l2,60
savefp %l2,62
!!! Do something
fxtod %f14,%f10
target:
! Save FP regs to memory after
savefp %l3,0
savefp %l3,2
savefp %l3,4
savefp %l3,6
savefp %l3,8
savefp %l3,10
savefp %l3,12
savefp %l3,14
savefp %l3,16
savefp %l3,18
savefp %l3,20
savefp %l3,22
savefp %l3,24
savefp %l3,26
savefp %l3,28
savefp %l3,30
savefp %l3,32
savefp %l3,34
savefp %l3,36
savefp %l3,38
savefp %l3,40
savefp %l3,42
savefp %l3,44
savefp %l3,46
savefp %l3,48
savefp %l3,50
savefp %l3,52
savefp %l3,54
savefp %l3,56
savefp %l3,58
savefp %l3,60
savefp %l3,62
=09
mov 0, %l1
setx .LLC0,%g1,%l0
loop:
mov %l0,%o0
ldx [%l2],%o2
ldx [%l3],%o3
call printf,0
mov %l1,%o1
add %l1,2,%l1
add %l3,8,%l3
cmp %l1,64
bne,pt %icc,loop
add %l2,8,%l2
=09
call exit, 0
mov 0, %o0
nop
.size main,(.-main)
.align 8
.section ".rodata1",#alloc
.align 8
=2ELLC0:
.asciz "%2d 0x%016lx 0x%016lx\n"
.type .LLC0,#object
.size .LLC0,24
.local foo
.common foo,256,8
.local bar
.common bar,256,8
.end
--hQiwHBbRI9kgIhsi--
--5QAgd0e35j3NYeGe
Content-Type: application/pgp-signature
Content-Disposition: inline
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.14 (FreeBSD)
iEYEARECAAYFAkuWIqkACgkQ/opHv/APuIeE8wCfZzqZD7Hj72KIGMGxflpNPg0p
QkUAniLoHon3YIZumV/60LtlGa524lf1
=Mpkc
-----END PGP SIGNATURE-----
--5QAgd0e35j3NYeGe--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20100309102753.GC3978>