On 2020/4/17 08:52, Segher Boessenkool wrote:
> Hi!
>
> On Mon, Apr 13, 2020 at 10:11:43AM +0800, luoxhu wrote:
>> frame_pointer_needed is set to true in reload pass setup_can_eliminate,
>> but regs_ever_live[31] is false, pro_and_epilogue uses it without live
>> check causing CPU2006 465.tonto segment fault of loading from invalid
>> addresses due to r31 not saved/restored. Thus, add HARD_FRAME_POINTER_REGNUM
>> live check with frame_pointer_needed_indeed_p when generating
>> pro_and_epilogue
>> instructions.
>
> I see.
>
> Can you instead make a boolean variable "frame_pointer_needed_indeed",
> that you set somewhere early in *logue processing? So that we can be
> sure that it will not change behind our backs.
Thanks, rs6000_emit_prologue seems the proper place to set the
frame_pointer_needed_indeed,
but it's strange that hard_frame_pointer_rtx will be marked USE in
make_prologue_seq, also
need check here though not causing segfault? PS, this piece of code is in
different file.
function.c
static rtx_insn *
make_prologue_seq (void)
{
if (!targetm.have_prologue ())
return NULL;
start_sequence ();
rtx_insn *seq = targetm.gen_prologue ();
emit_insn (seq);
/* Insert an explicit USE for the frame pointer
if the profiling is on and the frame pointer is required. */
if (crtl->profile && frame_pointer_needed)
emit_use (hard_frame_pointer_rtx);
...
Any way, update the patch as below with your previous comments:
This bug is exposed by FRE refactor of r263875. Comparing the fre
dump file shows no obvious change of the segment fault function proves
it to be a target issue.
frame_pointer_needed is set to true in reload pass setup_can_eliminate,
but regs_ever_live[31] is false, pro_and_epilogue uses it without live
check causing CPU2006 465.tonto segment fault of loading from invalid
addresses due to r31 not saved/restored. Thus, add HARD_FRAME_POINTER_REGNUM
live check with frame_pointer_needed_indeed when generating pro_and_epilogue
instructions.
Bootstrap and regression tested pass on Power8-LE. Backport to gcc-9
required once approved.
gcc/ChangeLog
2020-04-17 Xiong Hu Luo <[email protected]>
PR target/91518
* config/rs6000/rs6000-logue.c (frame_pointer_needed_indeed):
New variable.
(rs6000_emit_prologue_components):
Check with frame_pointer_needed_indeed.
(rs6000_emit_epilogue_components): Likewise.
(rs6000_emit_epilogue): Likewise.
(rs6000_emit_prologue): Set frame_pointer_needed_indeed.
---
gcc/config/rs6000/rs6000-logue.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/gcc/config/rs6000/rs6000-logue.c b/gcc/config/rs6000/rs6000-logue.c
index 4cbf228eb79..2213d1fa227 100644
--- a/gcc/config/rs6000/rs6000-logue.c
+++ b/gcc/config/rs6000/rs6000-logue.c
@@ -58,6 +58,8 @@ static bool rs6000_save_toc_in_prologue_p (void);
static rs6000_stack_t stack_info;
+/* Set if HARD_FRAM_POINTER_REGNUM is really needed. */
+static bool frame_pointer_needed_indeed = false;
/* Label number of label created for -mrelocatable, to call to so we can
get the address of the GOT section */
@@ -2735,9 +2737,9 @@ void
rs6000_emit_prologue_components (sbitmap components)
{
rs6000_stack_t *info = rs6000_stack_info ();
- rtx ptr_reg = gen_rtx_REG (Pmode, frame_pointer_needed
- ? HARD_FRAME_POINTER_REGNUM
- : STACK_POINTER_REGNUM);
+ rtx ptr_reg = gen_rtx_REG (Pmode, frame_pointer_needed_indeed
+ ? HARD_FRAME_POINTER_REGNUM
+ : STACK_POINTER_REGNUM);
machine_mode reg_mode = Pmode;
int reg_size = TARGET_32BIT ? 4 : 8;
@@ -2815,9 +2817,9 @@ void
rs6000_emit_epilogue_components (sbitmap components)
{
rs6000_stack_t *info = rs6000_stack_info ();
- rtx ptr_reg = gen_rtx_REG (Pmode, frame_pointer_needed
- ? HARD_FRAME_POINTER_REGNUM
- : STACK_POINTER_REGNUM);
+ rtx ptr_reg = gen_rtx_REG (Pmode, frame_pointer_needed_indeed
+ ? HARD_FRAME_POINTER_REGNUM
+ : STACK_POINTER_REGNUM);
machine_mode reg_mode = Pmode;
int reg_size = TARGET_32BIT ? 4 : 8;
@@ -2996,7 +2998,10 @@ rs6000_emit_prologue (void)
&& (lookup_attribute ("no_split_stack",
DECL_ATTRIBUTES (cfun->decl))
== NULL));
-
+
+ frame_pointer_needed_indeed
+ = frame_pointer_needed && df_regs_ever_live_p (HARD_FRAME_POINTER_REGNUM);
+
/* Offset to top of frame for frame_reg and sp respectively. */
HOST_WIDE_INT frame_off = 0;
HOST_WIDE_INT sp_off = 0;
@@ -3658,7 +3663,7 @@ rs6000_emit_prologue (void)
}
/* Set frame pointer, if needed. */
- if (frame_pointer_needed)
+ if (frame_pointer_needed_indeed)
{
insn = emit_move_insn (gen_rtx_REG (Pmode, HARD_FRAME_POINTER_REGNUM),
sp_reg_rtx);
@@ -4534,7 +4539,7 @@ rs6000_emit_epilogue (enum epilogue_type epilogue_type)
}
/* If we have a frame pointer, we can restore the old stack pointer
from it. */
- else if (frame_pointer_needed)
+ else if (frame_pointer_needed_indeed)
{
frame_reg_rtx = sp_reg_rtx;
if (DEFAULT_ABI == ABI_V4)
--
2.21.0.777.g83232e3864
