[Bug other/101949] New: git miscompiled with -flto -fipa-pta

[alex_y_xu at yahoo dot ca]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101949

            Bug ID: 101949
           Summary: git miscompiled with -flto -fipa-pta
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alex_y_xu at yahoo dot ca
  Target Milestone: ---

Created attachment 51313
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51313&action=edit
step 2 patch

steps to reproduce:

1. download and unpack git-2.33.0 (other versions may also work)
2. apply the attached patch to work around binutils bugs with duplicate
function names
3. make CFLAGS="-O2 -flto -fipa-pta" git git-remote-https
4. git clone https://github.com/Hello71/empty-project.git
5. PATH=$PWD:$PATH git -C empty-project fetch
6. objdump --disassemble=iterate_ref_map2 git

expected behavior:

step 5 succeeds. in step 6, function references %rsi at some point

actual behavior:

step 5 segfaults. in step 6, function never references %rsi (i.e. returns 0
without populating *oid)

additional behavior:

it works ok without -flto or without -fipa-pta, thus the non-reduced test case.

note that the patch is only required for step 6; step 5 fails even if the patch
is not applied.