On 3/2/21 3:37 PM, Ilya Leoshkevich via Gcc-patches wrote:
> Bootstrapped and regtested on x86_64-redhat-linux, ppc64le-redhat-linux
> and s390x-redhat-linux. Ok for master?
>
>
>
> Commit efb6bc55a93a ("fwprop: Allow (subreg (mem)) simplifications")
> introduced a check that was supposed to look at the propagated def's
> number of uses. It uses insn_info::num_uses (), which in reality
> returns the number of uses def's insn has. The whole change therefore
> works only by accident.
>
> Fix by looking at def_info's uses instead of insn_info's uses. This
> requires passing around def_info instead of insn_info.
>
> gcc/ChangeLog:
>
> 2021-03-02 Ilya Leoshkevich <i...@linux.ibm.com>
>
> * fwprop.c (def_has_single_use_p): New function.
> (fwprop_propagation::fwprop_propagation): Look at
> def_info's uses.
> (try_fwprop_subst_note): Use def_info instead of insn_info.
> (try_fwprop_subst_pattern): Likewise.
> (try_fwprop_subst_notes): Likewise.
> (try_fwprop_subst): Likewise.
> (forward_propagate_subreg): Likewise.
> (forward_propagate_and_simplify): Likewise.
> (forward_propagate_into): Likewise.
> * iterator-utils.h (single_element_p): New function.
Given we're well into stage4, I'd recommend deferring to gcc-12 unless
this fixes a code correctness issue.
Jeff
