> On 20 Aug 2018, at 08:27, Richard Biener <richard.guent...@gmail.com> wrote:
>
> On Tue, Aug 14, 2018 at 10:18 PM Mike Stump <mikest...@comcast.net> wrote:
>>
>> On Aug 14, 2018, at 4:20 AM, Iain Sandoe <i...@sandoe.co.uk> wrote:
>>> When function sub-sections are enabled, Darwin’s assembler needs the FDE
>>> local start
>>> label for each sub-section to follow a linker-visible one so that the FDE
>>> will be correctly
>>> associated with the code of the subsection.
>>>
>>> The current code in final.c emits a linker-visible symbol, as needed by
>>> several targets.
>>> However the local label used to define the FDE start precedes the
>>> linker-visible one
>>> which, for Darwin causes it (the FDE start) to be associated with the
>>> previous linker-
>>> visible symbol (or the section start if there isn’t one). This applies
>>> regardless of the
>>> actual address of the label, for toolchain assemblers that have strict
>>> interpretation of
>>> the Darwin sub-sections-via-symbols ABI.
>>>
>>> The patch adds a new local label (analogous to the "LFBn” emitted for the
>>> regular
>>> function starts) just after the linker-visible label emitted after
>>> switching text section.
>>> The FDE second entry is made to point to this instead of the LcoldStartn
>>> one. This
>>> should be a no-op for targets using .cfi_ and for targets without
>>> sub-sections-via-symbols.
>>>
>>> Bootstrapped on x86_64 and i686 linux and on a number of Darwin platforms
>>> (from
>>> i686-darwin9 to x86_64-darwin17).
>>>
>>> OK for trunk?
>>> open branches? (although it's a regression on 8, it’s a latent wrong-code
>>> on all branches)
>>
>> I'm fine with the darwin aspects of it, but I think it needs review/approval
>> by final.c/dwarf people.
>
> The approach looks fine (though we have extra labels even for targets
> that do not need it). But,
>
> + fde->dw_fde_second_begin = xstrdup (label);
>
> to me it looks like dw_fde_node is GC allocated so the above needs ggc_strdup.
Revised below, (bootstrapped Linux and Darwin).
OK to apply now?
thanks
Iain
gcc/
PR bootstrap/81033
PR target/81733
PR target/52795
* gcc/dwarf2out.c (FUNC_SECOND_SECT_LABEL): New.
(dwarf2out_switch_text_section): Generate a local label for the second
function sub-section and apply it as the second FDE start label.
* gcc/final.c (final_scan_insn_1): Emit second FDE label after the
second
sub-section start.
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 236f199..6a66de7 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -297,6 +297,10 @@ static unsigned int rnglist_idx;
#define FUNC_BEGIN_LABEL "LFB"
#endif
+#ifndef FUNC_SECOND_SECT_LABEL
+#define FUNC_SECOND_SECT_LABEL "LFSB"
+#endif
+
#ifndef FUNC_END_LABEL
#define FUNC_END_LABEL "LFE"
#endif
@@ -1212,21 +1216,24 @@ static void set_cur_line_info_table (section *);
void
dwarf2out_switch_text_section (void)
{
+ char label[MAX_ARTIFICIAL_LABEL_BYTES];
section *sect;
dw_fde_ref fde = cfun->fde;
gcc_assert (cfun && fde && fde->dw_fde_second_begin == NULL);
+ ASM_GENERATE_INTERNAL_LABEL (label, FUNC_SECOND_SECT_LABEL,
+ current_function_funcdef_no);
+
+ fde->dw_fde_second_begin = ggc_strdup (label);
if (!in_cold_section_p)
{
fde->dw_fde_end = crtl->subsections.cold_section_end_label;
- fde->dw_fde_second_begin = crtl->subsections.hot_section_label;
fde->dw_fde_second_end = crtl->subsections.hot_section_end_label;
}
else
{
fde->dw_fde_end = crtl->subsections.hot_section_end_label;
- fde->dw_fde_second_begin = crtl->subsections.cold_section_label;
fde->dw_fde_second_end = crtl->subsections.cold_section_end_label;
}
have_multiple_function_sections = true;
diff --git a/gcc/final.c b/gcc/final.c
index 842e5e0..6943c07 100644
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -2232,6 +2232,9 @@ final_scan_insn_1 (rtx_insn *insn, FILE *file, int
optimize_p ATTRIBUTE_UNUSED,
ASM_OUTPUT_LABEL (asm_out_file,
IDENTIFIER_POINTER (cold_function_name));
#endif
+ if (dwarf2out_do_frame ()
+ && cfun->fde->dw_fde_second_begin != NULL)
+ ASM_OUTPUT_LABEL (asm_out_file, cfun->fde->dw_fde_second_begin);
}
break;
