On 12/13/2016 05:05 PM, Eric Botcazou wrote:
Hi,
the Ada runtime library doesn't build on SPARC 32-bit with LRA because of an
ICE on a couple of files:
eric@polaris:~/build/gcc/sparc-sun-solaris2.10> gcc/gnat1 -I gcc/ada/rts -
quiet -dumpbase g-debpoo.adb -auxbase g-debpoo -O2 -gnatpg -fPIC -mlra -
mcpu=v9 g-debpoo.adb -o g-debpoo.s
+===========================GNAT BUG DETECTED==============================+
| 7.0.0 20161213 (experimental) [trunk revision 243595] (sparc-sun-
solaris2.10) GCC error:|
| in lra_set_insn_recog_data, at lra.c:965 |
| Error detected around g-debpoo.adb:1896:8
The problem is that curr_insn_transform attempts to reload subregs before
reloading addresses:
if (! check_only_p)
/* Make equivalence substitution and memory subreg elimination
before address processing because an address legitimacy can
depend on memory mode. */
Now, on strict-alignment platforms, simplify_operand_subreg has a special
provision for paradoxical subregs of memory references:
/* If we change the address for a paradoxical subreg of memory, the
address might violate the necessary alignment or the access might
be slow. So take this into consideration. We need not worry
about accesses beyond allocated memory for paradoxical memory
subregs as we don't substitute such equiv memory (see processing
equivalences in function lra_constraints) and because for spilled
pseudos we allocate stack memory enough for the biggest
corresponding paradoxical subreg. */
if (!(MEM_ALIGN (reg) < GET_MODE_ALIGNMENT (mode)
&& SLOW_UNALIGNED_ACCESS (mode, MEM_ALIGN (reg)))
|| (MEM_ALIGN (reg) < GET_MODE_ALIGNMENT (innermode)
&& SLOW_UNALIGNED_ACCESS (innermode, MEM_ALIGN (reg))))
return true;
That is to say, if the adjusted memory reference is not sufficient aligned,
the routine will reload the original memory reference instead of the adjusted
one on strict-alignment platforms. But there is a hitch: if the address of
this original memory reference is invalid, the routine will nevertheless
reload the entire memory reference, leading to the aforementioned ICE.
The proposed fix is to reload the address, if it is invalid, just before
reloading the memory reference in simplify_operand_subreg; this yields the
correct sequence of reloads for the case I investigated. The patch also
contains formatting fixes and adds a 'return' for the sake of clarity.
Tested on x86-64/Linux and SPARC/Solaris with LRA, OK for the mainline?
OK. Thanks for working on this issue, Eric.
The subreg reload code is very sensitive to changes and actually had a
lot of changes. So we should be aware that the patch might create new
PRs. But I believe the probability of this is tiny.
2016-12-13 Eric Botcazou <ebotca...@adacore.com>
* lra-constraints.c (process_address): Add forward declaration.
(simplify_operand_subreg): In the MEM case, if the adjusted memory
reference is not sufficient aligned and the address was invalid,
reload the address before reloading the original memory reference.
Fix long lines and add a final return for the sake of clarity.
