[Bug rtl-optimization/104153] New: [12 Regression] ICE due to recent ifcvt changes

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104153

            Bug ID: 104153
           Summary: [12 Regression] ICE due to recent ifcvt changes
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: law at gcc dot gnu.org
  Target Milestone: ---

Created attachment 52249
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52249&action=edit
Testcase

or1k-elf has started regressing building newlib after this patch:

commit aa8cfe785953a0e87d2472311e1260cd98c605c0 (HEAD)
Author: Robin Dapp <rdapp@linux.ibm.com>
Date:   Wed Jan 19 17:36:36 2022 +0100

    ifcvt: Try re-using CC for conditional moves.

    Following up on the previous patch, this patch makes
    noce_convert_multiple emit two cmov sequences:  The same one as before
    and a second one that tries to re-use the existing CC.  Then their costs
    are compared and the cheaper one is selected.

    gcc/ChangeLog:

            * ifcvt.cc (cond_exec_get_condition): New parameter to allow
getting the
            reversed comparison.
            (try_emit_cmove_seq): New function to facilitate creating a cmov
            sequence.
            (noce_convert_multiple_sets): Create two sequences and use the less
            expensive one.


It's faulting a bit later in the RTL pipeline, but I think what's going on is
we're modifying an insn in-place and don't update the DF information leading to
a DF verification failure later.  I'd bet if we did a full DF verify after
ifcvt we'd see the failure earlier.

Compile the attached code with -O2 on an or1k-elf cross-compiler to get:

dump file: j.c.276r.cprop3

../../../../../../..//newlib-cygwin/newlib/libm/math/s_floor.c: In function
‘floor’:
../../../../../../..//newlib-cygwin/newlib/libm/math/s_floor.c:121:1: internal
compiler error: in df_refs_verify, at df-scan.cc:4003
0xca95c6 df_refs_verify
        /home/jlaw/test/gcc/gcc/df-scan.cc:4003
0xca9836 df_insn_refs_verify
        /home/jlaw/test/gcc/gcc/df-scan.cc:4086
0xca99d7 df_bb_verify
        /home/jlaw/test/gcc/gcc/df-scan.cc:4119
0xca9fa5 df_scan_verify()
        /home/jlaw/test/gcc/gcc/df-scan.cc:4240
0xc94512 df_verify()
        /home/jlaw/test/gcc/gcc/df-core.cc:1818
0xc92e0c df_analyze_1
        /home/jlaw/test/gcc/gcc/df-core.cc:1214
0xc931d0 df_analyze()
        /home/jlaw/test/gcc/gcc/df-core.cc:1290
0x1dc4925 execute_rtl_cprop
        /home/jlaw/test/gcc/gcc/cprop.cc:1925
0x1dc4a24 execute
        /home/jlaw/test/gcc/gcc/cprop.cc:1964