Hi Markus, Hi Richard,
PR 70044 reports a problem with the AArch64 backend. With LTO enabled
the function aarch64_override_options_after_change can be called more
than once for the same function. If only leaf frame pointers were
being omitted originally, then the first call will set
flag_omit_frame_pointer to true. Then the second call will set
flag_omit_leaf_frame_pointer to false, thus forcing the frame pointer
to always be omitted, contrary to the original settings of these
flags.
The attached patch fixes this problem by setting
flag_omit_frame_pointer to true, but using a special value of 2 to do
so. Then when the second call occurs we can detect this case and
ensure that we do not set flag_omit_leaf_frame_pointer to false.
Tested with no regressions on an aarch64-elf toolchain.
OK to apply ?
Cheers
Nick
gcc/ChangeLog
2016-03-04 Nick Clifton <ni...@redhat.com>
PR target/7044
* config/aarch64/aarch64.c
(aarch64_override_options_after_change_1): When forcing
flag_omit_frame_pointer to be true, use a special value that can
be detected if this function is called again, thus preventing
flag_omit_leaf_frame_pointer from being forced to be false.
Index: gcc/config/aarch64/aarch64.c
===================================================================
--- gcc/config/aarch64/aarch64.c (revision 233960)
+++ gcc/config/aarch64/aarch64.c (working copy)
@@ -8110,6 +8110,21 @@
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)
