Store estimated istrances in compressed_size

elf_x86_64_convert_load is very time consuming since it is called on
each input section and has a loop over input text sections to estimate
the branch distrance.  We can store the estimated distrances in the
compressed_size field of the output section, which is only used to
decompress the compressed input section.

Before the patch, linking clang 3.9 takes 52 seconds.  After the patch,
it only takes 2.5 seconds.

	PR ld/19542
	* elf64-x86-64.c (elf_x86_64_convert_load): Store the estimated
	distrances in the compressed_size field of the output section.

1 files changed, 23 insertions, 15 deletions

diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index 88ed00e..8118c1d 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -3190,35 +3190,43 @@ elf_x86_64_convert_load (bfd *abfd, asection *sec,
 	}
       else
 	{
-	  asection *asect;
-	  bfd_size_type size;
+	  bfd_signed_vma distance;
 
 	  /* At this point, we don't know the load addresses of TSEC
 	     section nor SEC section.  We estimate the distrance between
-	     SEC and TSEC.  */
-	  size = 0;
-	  for (asect = sec->output_section;
-	       asect != NULL && asect != tsec->output_section;
-	       asect = asect->next)
+	     SEC and TSEC.  We store the estimated distrances in the
+	     compressed_size field of the output section, which is only
+	     used to decompress the compressed input section.  */
+	  if (sec->output_section->compressed_size == 0)
 	    {
-	      asection *i;
-	      for (i = asect->output_section->map_head.s;
-		   i != NULL;
-		   i = i->map_head.s)
+	      asection *asect;
+	      bfd_size_type size = 0;
+	      for (asect = link_info->output_bfd->sections;
+		   asect != NULL;
+		   asect = asect->next)
 		{
-		  size = align_power (size, i->alignment_power);
-		  size += i->size;
+		  asection *i;
+		  for (i = asect->map_head.s;
+		       i != NULL;
+		       i = i->map_head.s)
+		    {
+		      size = align_power (size, i->alignment_power);
+		      size += i->size;
+		    }
+		  asect->compressed_size = size;
 		}
 	    }
 
 	  /* Don't convert GOTPCREL relocations if TSEC isn't placed
 	     after SEC.  */
-	  if (asect == NULL)
+	  distance = (tsec->output_section->compressed_size
+		      - sec->output_section->compressed_size);
+	  if (distance < 0)
 	    continue;
 
 	  /* Take PT_GNU_RELRO segment into account by adding
 	     maxpagesize.  */
-	  if ((toff + size + maxpagesize - roff + 0x80000000)
+	  if ((toff + distance + maxpagesize - roff + 0x80000000)
 	      > 0xffffffff)
 	    continue;
 	}