[PATCH 1/2] Gold: Skip zero-sized sections for ICF

[Fangrui Song]

On 2020-10-11, H.J. Lu via Binutils wrote:
>Skip zero-sized sections since there is no need to do ICF on them.
>
>	* icf.cc (Icf::find_identical_sections): Skip zero-sized sections.
>---
> gold/icf.cc | 2 ++
> 1 file changed, 2 insertions(+)
>
>diff --git a/gold/icf.cc b/gold/icf.cc
>index a60db7abc8d..54af4126696 100644
>--- a/gold/icf.cc
>+++ b/gold/icf.cc
>@@ -973,6 +973,8 @@ Icf::find_identical_sections(const Input_objects* input_objects,
>
>       for (unsigned int i = 0; i < (*p)->shnum(); ++i)
>         {
>+          if ((*p)->section_size(i) == 0)
>+            continue;
> 	  const std::string section_name = (*p)->section_name(i);
>           if (!is_section_foldable_candidate(section_name))
> 	    {
>-- 
>2.26.2
>

Does anything break without the special case? ld.lld --icf={all,safe} does not
special case st_size=0


.section .text.1,"ax"; .globl foo; foo:
.section .text.2,"ax"; .globl bar; bar:

% ld.lld a.o --icf=all --print-icf-sections
selected section a.o:(.text)
   removing identical section a.o:(.text.1)
   removing identical section a.o:(.text.2)
ld.lld: warning: cannot find entry symbol _start; defaulting to 0x201158