Re: [PATCH] PR gold/17704

[Alan Modra <amodra at gmail dot com>]

On Thu, Jul 14, 2016 at 11:48:39AM -0700, Sriraman Tallam wrote:
> @@ -671,7 +667,31 @@ match_sections(unsigned int iteration_num,
>                           this_secn_contents.c_str(),
>                           this_secn_contents.length()) != 0)
>                    continue;
> -              (*kept_section_id)[i] = kept_section;
> +
> +	      // Check section alignment here.
> +              // The section with the larger alignment requirement
> +              // should be kept. Do not fold if the larger is not
> +              // divisible by the smaller, but that case will never
> +              // happen if the alignments are powers of 2.
> +              uint64_t align_i = section_addraligns[i];
> +              uint64_t align_kept = section_addraligns[kept_section];
> +              if (align_i <= align_kept)
> +                {
> +                  if (align_i != align_kept && align_i != 0
> +		      && (align_kept % align_i) != 0)
> +                      continue;
> +                  (*kept_section_id)[i] = kept_section;
> +                }
> +              else
> +                {
> +                  if (align_kept != 0 && (align_i % align_kept) != 0)
> +                      continue;
> +                  (*kept_section_id)[kept_section] = i;
> +                  it->second = i;
> +                  full_section_contents[kept_section].swap(
> +                      full_section_contents[i]);
> +                }
> +
>                converged = false;
>                break;
>              }

The gabi says of sh_addralign "Currently, only 0 and positive integral
powers of two are allowed", so I think you can discount the
possibility of alignment not a power of two.  It's not worth
supporting here when other parts of gold do not, eg. see layout.cc
calls to align_address.

Please also fix indentation, only some of the above lines use tabs.

> diff --git a/gold/testsuite/Makefile.am b/gold/testsuite/Makefile.am
> index c8d3093..7b9b267 100644
> --- a/gold/testsuite/Makefile.am
> +++ b/gold/testsuite/Makefile.am
> @@ -355,6 +355,12 @@ icf_sht_rel_addend_test: icf_sht_rel_addend_test_1.o icf_sht_rel_addend_test_2.o
>  icf_sht_rel_addend_test.stdout: icf_sht_rel_addend_test
>  	$(TEST_NM) icf_sht_rel_addend_test > icf_sht_rel_addend_test.stdout
>  
> +check_PROGRAMS += pr17704a_test
> +pr17704a_test.o: pr17704a_test.s
> +	$(TEST_AS) --64  -o $@ $<
> +pr17704a_test: pr17704a_test.o gcctestdir/ld
> +	gcctestdir/ld --icf=all -o $@ $<
> +
>  check_PROGRAMS += large_symbol_alignment
>  large_symbol_alignment_SOURCES = large_symbol_alignment.cc
>  large_symbol_alignment_DEPENDENCIES = gcctestdir/ld

The new test contains x86 assembly, but is enabled for all native
targets using gcc.  Please move to a more appropriate part of the
makefile.

-- 
Alan Modra
Australia Development Lab, IBM