Eric Botcazou wrote: > Reload 1 of insn #85 inherits the reload reg from reload 1 of insn #84, the > bug being that the same reload reg is also used for reload 0 of insn #85. > > This is supposed to work like so: the inheritance code in choose_reload_regs > calls free_for_value_p with IGNORE_ADDRESS_RELOADS set to 1 to bypass the > conflict with reload 0 because there is special code in the same function to > discard reload 0 in this case: > > /* If we can inherit a RELOAD_FOR_INPUT, or can use a > reload_override_in, then we do not need its related > RELOAD_FOR_INPUT_ADDRESS / RELOAD_FOR_INPADDR_ADDRESS reloads; > likewise for other reload types. > We handle this by removing a reload when its only replacement > is mentioned in reload_in of the reload we are going to inherit. > A special case are auto_inc expressions; even if the input is > inherited, we still need the address for the output. We can > recognize them because they have RELOAD_OUT set to RELOAD_IN. > If we succeeded removing some reload and we are doing a > preliminary > pass just to remove such reloads, make another pass, since the > removal of one reload might allow us to inherit another one. */ > else if (rld[r].in > && rld[r].out != rld[r].in > && remove_address_replacements (rld[r].in) && pass) > pass = 2; > > But it is called with rld[r].in equal to: > (gdb) p debug_rtx(in_rtx) > (reg:SI 40 %f8 [orig:109 prephitmp.12 ] [109]) > > and the following replacement for reload 0: > (gdb) p debug_rtx(*replacements[0].where) > (plus:SI (reg/f:SI 30 %fp) > (const_int -6140 [0xffffffffffffe804])) > > so loc_mentioned_in_p returns false and reload 0 isn't discarded. > > The problem is that reload 0 is pushed because of SECONDARY_MEMORY_NEEDED, > i.e. (reg:SI 40 %f8) is spilled to memory at the address > (gdb) p debug_rtx(secondary_memlocs_elim[11][0]) > (mem/c:SI (plus:SI (reg/f:SI 30 %fp) > (const_int -6140 [0xffffffffffffe804])) [0 S4 A32]) > > and replacements[0].where above points to within this MEM instead of IN_RTX.
This analysis looks correct to me. > The attached patch fixes the problem (on the 4.6 branch) by also invoking > remove_address_replacements on the result of get_secondary_mem if a secondary > memory is needed. The condition to detect it has been copied from > push_reload > on the 4.6 branch, but it has already slightly changed on the mainline and > I'm > not sure how to adjust it. It is unfortunate that we need to re-do the test over and over ... longer term it might be better to add a predicate to directly *check* whether we decided we needed a secondary memory slot for the operand. In any case, the change in the condition you noticed was introduced by a recent patch by Bernd: http://gcc.gnu.org/ml/gcc-patches/2012-08/msg00171.html It seems that we ought to use a similar test to what Bernd introduced in gen_reload, that is, use the "replaced_subreg" routine on rld[r].in, check whether the result is a hard register and use its REGNO_REG_CLASS. Bernd, given that you worked on this recently, any other thoughts? Bye, Ulrich -- Dr. Ulrich Weigand GNU Toolchain for Linux on System z and Cell BE ulrich.weig...@de.ibm.com
