#364: ptr_alignment 8 not honored, sparc 64bit broken
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Reporter: rurban | Owner: rurban
Type: bug | Status: assigned
Priority: blocker | Milestone: 1.0
Component: core | Version: trunk
Severity: release | Keywords:
Lang: | Patch:
Platform: other |
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Description changed by rurban:
Old description:
> Sparc 64bit with strict ptr_alignment=8 breaks when reading frozen pmc's
> because of misalignment.
>
> Any 64bit big-endian cpu with strict alignment is broken without
> '''-xmemalign=2i''' (the immediate workaround)
> The default for all v9 architectures is '''-xmemalign=8s'''.
>
> However, our goal should be to allow fast aligned code and not to skip
> this with a compiler relaxement.
>
> {{{
> * First we should align to the foreign pbc ptrsize, not to the native
> ptrsize.
> * /sizeof (opcode_t) => /header->wordsize
> */
> #define ROUND_16(val) (((val) & 0xf) ? 16 - ((val) & 0xf) : 0)
> #define ALIGN_16(st, cursor) \
> (cursor) += ROUND_16((const char *)(cursor) - (const char
> *)(st))/sizeof (opcode_t)
> }}}
>
> This requires a check for all ptr alignment code (no macros used, bad)
> and to find the source of the problem, most likely a string.
>
> {{{
> t...@1 (l...@1) stopped in PF_fetch_integer at line 1076 in file "pf_items.c"
> 1076 ASSERT_ARGS(PF_fetch_integer)
> (dbx) step
> t...@1 (l...@1) stopped in PF_fetch_integer at line 1078 in file "pf_items.c"
> 1078 if (!pf || pf->fetch_iv == NULL)
> (dbx) print *(*stream)
> **stream = 4
> (dbx) step
> t...@1 (l...@1) stopped in PF_fetch_integer at line 1079 in file "pf_items.c"
> 1079 return *(*stream)++;
> (dbx) print *(*stream)
> **stream = 4
> (dbx) step
> t...@1 (l...@1) signal BUS (invalid address alignment) in PF_fetch_integer at
> line 1079 in file "pf_items.c"
> 1079 return *(*stream)++;
> (dbx) print *(*stream)
> **stream = 35
> (dbx) print *stream
> *stream = 0x100000dec
> }}}
>
> '''0x100000dec''' is not properly aligned. It must be '''0x100000df0'''.
>
> Sparc cc manpage:[[BR]]
> -xmemalign[=<a><b>] Controls memory alignment, <a>={1|2|4|8|16},
> b={f|i|s}.[[BR]]
> Accepted values for b are: i Interpret access and continue execution. s
> Raise signal SIGBUS. f For variants of -xarch=v9 only. [reduced i]
>
> Thanks to Rolf Grossmann for coming up with all this info and debugging,
> and to Andy Dougherty for correcting my wrong first analysis.
New description:
Sparc 64bit with strict ptr_alignment=8 breaks when reading frozen pmc's
because of misalignment.
Any 64bit big-endian cpu with strict alignment is broken without
'''-xmemalign=4s''' (the immediate workaround)
The default for all v9 architectures is '''-xmemalign=8s'''.
However, our goal should be to allow fast aligned code and not to skip
this with a compiler relaxement.
{{{
t...@1 (l...@1) stopped in PF_fetch_integer at line 1076 in file "pf_items.c"
1076 ASSERT_ARGS(PF_fetch_integer)
(dbx) step
t...@1 (l...@1) stopped in PF_fetch_integer at line 1078 in file "pf_items.c"
1078 if (!pf || pf->fetch_iv == NULL)
(dbx) print *(*stream)
**stream = 4
(dbx) step
t...@1 (l...@1) stopped in PF_fetch_integer at line 1079 in file "pf_items.c"
1079 return *(*stream)++;
(dbx) print *(*stream)
**stream = 4
(dbx) step
t...@1 (l...@1) signal BUS (invalid address alignment) in PF_fetch_integer at
line 1079 in file "pf_items.c"
1079 return *(*stream)++;
(dbx) print *(*stream)
**stream = 35
(dbx) print *stream
*stream = 0x100000dec
}}}
'''0x100000dec''' is not properly aligned. It must be '''0x100000df0'''.
Sparc cc manpage:[[BR]]
-xmemalign[=<a><b>] Controls memory alignment, <a>={1|2|4|8|16},
b={f|i|s}.[[BR]]
Accepted values for b are:[[BR]]
i Interpret access and continue execution.[[BR]]
s Raise signal SIGBUS. [[BR]]
f For variants of -xarch=v9 only. [reduced i] [[BR]]
Thanks to Rolf Grossmann for coming up with all this info and debugging,
and to Andy Dougherty for correcting my wrong first analysis.
The fix for 1.0 will be a hints file update to add -xmemalign=4s to
cc_flags, the goal for 2.6 will be a --64bitcompat argument to parrot to
create 8-byte aligned values on 32-bit, not 4-byte as now.
--
--
Ticket URL: <https://trac.parrot.org/parrot/ticket/364#comment:10>
Parrot <https://trac.parrot.org/parrot/>
Parrot Development
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