[PATCH] x86: Restore the frame pointer in word_mode

[H.J. Lu via Gcc-patches]

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);
 
              /* 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