[gcc r12-9840] LoongArch: Fix bug in loongarch_emit_stack_tie [PR110484].

[gcc r12-9840] LoongArch: Fix bug in loongarch_emit_stack_tie [PR110484].

[LuluCheng]

https://gcc.gnu.org/g:d60c00492eb5818493560f299f06d1e3d9efcc69

commit r12-9840-gd60c00492eb5818493560f299f06d1e3d9efcc69
Author: Lulu Cheng <chenglulu@loongson.cn>
Date:   Thu Jun 29 19:30:59 2023 +0800

    LoongArch: Fix bug in loongarch_emit_stack_tie [PR110484].
    
    Which may result in implicit references to $fp when frame_pointer_needed is false,
    causing regs_ever_live[$fp] to be true when $fp is not explicitly used,
    resulting in $fp being used as the target replacement register in the rnreg pass.
    
    The bug originates from SPEC2017 541.leela_r(-flto).
    
    gcc/ChangeLog:
    
            PR target/110484
            * config/loongarch/loongarch.cc (loongarch_emit_stack_tie): Use the
            frame_pointer_needed to determine whether to use the $fp register.
    
    Co-authored-by: Guo Jie <guojie@loongson.cn>
    
    (cherry picked from commit 1967f21d000e09d3d3190317af7923b578ce02b1)

Diff:
---
 gcc/config/loongarch/loongarch.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
index 22901cb61010..9cc9c74cd73d 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -1098,7 +1098,9 @@ loongarch_first_stack_step (struct loongarch_frame_info *frame)
 static void
 loongarch_emit_stack_tie (void)
 {
-  emit_insn (gen_stack_tie (Pmode, stack_pointer_rtx, hard_frame_pointer_rtx));
+  emit_insn (gen_stack_tie (Pmode, stack_pointer_rtx,
+			    frame_pointer_needed ? hard_frame_pointer_rtx
+			    : stack_pointer_rtx));
 }
 
 #define PROBE_INTERVAL (1 << STACK_CHECK_PROBE_INTERVAL_EXP)