ping
From: Wilco Dijkstra
Sent: 04 August 2017 16:46
To: GCC Patches; James Greenhalgh
Cc: nd
Subject: [PATCH][AArch64] PR60580: Fix frame pointer option magic
To fix PR60580 simplify the logic in aarch64_override_options_after_change_1 ().
If the frame pointer is enabled, set it to a special value that behaves similar
to frame pointer omission. If we don't do this all leaf functions will get a
frame pointer even if flag_omit_leaf_frame_pointer is set.
If flag_omit_frame_pointer has this special value, we must force the frame
pointer if not in a leaf function. We also need to force it in a leaf function
if flag_omit_frame_pointer is not set or if LR is used.
Doing this allows both -fomit-frame-pointer and -fomit-leaf-frame-pointer to be
independently set and changed in each function with the expected behaviour.
OK for commit and backport to GCC7/GCC6?
ChangeLog:
2017-08-04 Wilco Dijkstra <wdijk...@arm.com>
gcc/
PR middle-end/60580
* config/aarch64/aarch64.c (aarch64_frame_pointer_required)
Check special value of flag_omit_frame_pointer.
(aarch64_can_eliminate): Likewise.
(aarch64_override_options_after_change_1): Simplify handling of
-fomit-frame-pointer and -fomit-leaf-frame-pointer.
--
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index
f90420bffe841155d2ea12dc7450fa699718e8ae..8ec196bca5e7203f2bb38381fe89b1aec43b9a29
100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -2839,12 +2839,13 @@ aarch64_output_probe_stack_range (rtx reg1, rtx reg2)
static bool
aarch64_frame_pointer_required (void)
{
- /* In aarch64_override_options_after_change
- flag_omit_leaf_frame_pointer turns off the frame pointer by
- default. Turn it back on now if we've not got a leaf
- function. */
- if (flag_omit_leaf_frame_pointer
- && (!crtl->is_leaf || df_regs_ever_live_p (LR_REGNUM)))
+ /* Use the frame pointer if enabled and it is not a leaf function, unless
+ leaf frame pointer omission is disabled. If the frame pointer is enabled,
+ force the frame pointer in leaf functions which use LR. */
+ if (flag_omit_frame_pointer == 2
+ && !(flag_omit_leaf_frame_pointer
+ && crtl->is_leaf
+ && !df_regs_ever_live_p (LR_REGNUM)))
return true;
/* Force a frame pointer for EH returns so the return address is at FP+8. */
@@ -5892,6 +5893,7 @@ aarch64_can_eliminate (const int from, const int to)
LR in the function, then we'll want a frame pointer after all, so
prevent this elimination to ensure a frame pointer is used. */
if (to == STACK_POINTER_REGNUM
+ && flag_omit_frame_pointer == 2
&& flag_omit_leaf_frame_pointer
&& df_regs_ever_live_p (LR_REGNUM))
return false;
@@ -8914,24 +8916,16 @@ aarch64_parse_override_string (const char* input_string,
static void
aarch64_override_options_after_change_1 (struct gcc_options *opts)
{
- /* The logic here is that if we are disabling all frame pointer generation
- then we do not need to disable leaf frame pointer generation as a
- separate operation. But if we are *only* disabling leaf frame pointer
- generation then we set flag_omit_frame_pointer to true, but in
- aarch64_frame_pointer_required we return false only for leaf functions.
-
- PR 70044: We have to be careful about being called multiple times for the
- same function. Once we have decided to set flag_omit_frame_pointer just
- so that we can omit leaf frame pointers, we must then not interpret a
- second call as meaning that all frame pointer generation should be
- omitted. We do this by setting flag_omit_frame_pointer to a special,
- non-zero value. */
- if (opts->x_flag_omit_frame_pointer == 2)
- opts->x_flag_omit_frame_pointer = 0;
-
- if (opts->x_flag_omit_frame_pointer)
- opts->x_flag_omit_leaf_frame_pointer = false;
- else if (opts->x_flag_omit_leaf_frame_pointer)
+ /* PR 70044: We have to be careful about being called multiple times for the
+ same function. This means all changes should be repeatable. */
+
+ /* If the frame pointer is enabled, set it to a special value that behaves
+ similar to frame pointer omission. If we don't do this all leaf functions
+ will get a frame pointer even if flag_omit_leaf_frame_pointer is set.
+ If flag_omit_frame_pointer has this special value, we must force the
+ frame pointer if not in a leaf function. We also need to force it in a
+ leaf function if flag_omit_frame_pointer is not set or if LR is used. */
+ if (opts->x_flag_omit_frame_pointer == 0)
opts->x_flag_omit_frame_pointer = 2;
/* If not optimizing for size, set the default
