[Bug target/114936] New: [14/15 Regression] Typo in aarch64-ldp-fusion.cc:combine_reg_notes

[acoplan at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114936

            Bug ID: 114936
           Summary: [14/15 Regression] Typo in
                    aarch64-ldp-fusion.cc:combine_reg_notes
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: acoplan at gcc dot gnu.org
  Target Milestone: ---

aarch64-ldp-fusion.cc:combine_reg_notes has:

  result = filter_notes (REG_NOTES (i2->rtl ()), result,
                         &found_eh_region, fr_expr);
  result = filter_notes (REG_NOTES (i1->rtl ()), result,
                         &found_eh_region, fr_expr + 1);

  if (!load_p)
    {
      // Simple frame-related sp-relative saves don't need CFI notes, but when
      // we combine them into an stp we will need a CFI note as dwarf2cfi can't
      // interpret the unspec pair representation directly.
      if (RTX_FRAME_RELATED_P (i1->rtl ()) && !fr_expr[0])
        fr_expr[0] = copy_rtx (PATTERN (i1->rtl ()));
      if (RTX_FRAME_RELATED_P (i2->rtl ()) && !fr_expr[1])
        fr_expr[1] = copy_rtx (PATTERN (i2->rtl ()));
    }

so any REG_FRAME_RELATED_EXPR from i2 goes to fr_expr[0] and likewise i1 goes
to fr_expr[1], but then we have the opposite association inside the if
statement.

Many thanks to Matthew Malcomson for pointing this out to me.

I'm going to post the (arguably obvious) patch after testing that writes to
fr_expr + 1 first when we call filter_notes for i2.  We may want to consider a
backport to GCC 14 too.