On Sun, Apr 12, 2020 at 11:28 PM H.J. Lu <hjl.to...@gmail.com> wrote: > > We must restore the frame pointer in word_mode for eh_return epilogues > since the upper 32 bits of RBP register can have any values. > > Tested on Linux/x32 and Linux/x86-64. OK for master and backport to > GCC 8/9 branches? > > Thanks. > > H.J. > --- > PR target/94556 > * config/i386/i386.c (ix86_expand_epilogue): Restore the frame > pointer in word_mode for eh_return epilogues. > --- > gcc/config/i386/i386.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c > index ca3b7dc06c2..f9c8f75b559 100644 > --- a/gcc/config/i386/i386.c > +++ b/gcc/config/i386/i386.c > @@ -9052,8 +9052,14 @@ ix86_expand_epilogue (int style) > t = plus_constant (Pmode, t, m->fs.fp_offset - UNITS_PER_WORD); > emit_insn (gen_rtx_SET (sa, t)); > > - t = gen_frame_mem (Pmode, hard_frame_pointer_rtx); > - insn = emit_move_insn (hard_frame_pointer_rtx, t); > + /* NB: eh_return epilogues must restore the frame pointer > + in word_mode since the upper 32 bits of RBP register > + can have any values. */ > + t = gen_frame_mem (word_mode, hard_frame_pointer_rtx); > + rtx frame_reg = hard_frame_pointer_rtx; > + if (Pmode != word_mode) > + frame_reg = gen_rtx_REG (word_mode, REGNO (frame_reg)); > + insn = emit_move_insn (frame_reg, t);
I didn't test it myself, but it looks to me that you can use "rtx frame_reg = gen_rtx_REG (word_mode, HARD_FRAME_POINTER_REGNUM);" unconditionally, since gen_rtx_REG has some bypass code to return hard_frame_pointer_rtx when appropriate. I don't know x32 enough for a functional review, so LGTM with the above change. Please wait a week before backporting the patch. Thanks, Uros. > /* Note that we use SA as a temporary CFA, as the return > address is at the proper place relative to it. We > @@ -9068,7 +9074,7 @@ ix86_expand_epilogue (int style) > add_reg_note (insn, REG_CFA_DEF_CFA, > plus_constant (Pmode, sa, UNITS_PER_WORD)); > ix86_add_queued_cfa_restore_notes (insn); > - add_reg_note (insn, REG_CFA_RESTORE, hard_frame_pointer_rtx); > + add_reg_note (insn, REG_CFA_RESTORE, frame_reg); > RTX_FRAME_RELATED_P (insn) = 1; > > m->fs.cfa_reg = sa; > -- > 2.25.2 >
