Use stable sort for ld -r relocs

A number of targets emit multiple relocs at a given r_offset, and
depend on those relocs staying in their original order.

	PR 18867
	* elflink.c (cmp_ext32l_r_offset, cmp_ext32b_r_offset): Delete.
	(cmp_ext64l_r_offset, cmp_ext64b_r_offset): Delete.
	(ext32l_r_offset, ext32b_r_offset, ext64l_r_offset, ext64b_r_offset):
	New functions.
	(elf_link_adjust_relocs): Use an insertion sort to sort relocs.

2 files changed, 86 insertions, 72 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 52fe2cc..00035c4 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,12 @@
+2015-08-26  Alan Modra  <amodra@gmail.com>
+
+	PR 18867
+	* elflink.c (cmp_ext32l_r_offset, cmp_ext32b_r_offset): Delete.
+	(cmp_ext64l_r_offset, cmp_ext64b_r_offset): Delete.
+	(ext32l_r_offset, ext32b_r_offset, ext64l_r_offset, ext64b_r_offset):
+	New functions.
+	(elf_link_adjust_relocs): Use an insertion sort to sort relocs.
+
 2015-08-26  Matthew Fortune  <matthew.fortune@imgtec.com>
 
 	PR ld/18401
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 76f6493..192ce15 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -8102,10 +8102,12 @@ bfd_elf_perform_complex_relocation (bfd *input_bfd,
   return r;
 }
 
-/* qsort comparison functions sorting external relocs by r_offset.  */
+/* Functions to read r_offset from external (target order) reloc
+   entry.  Faster than bfd_getl32 et al, because we let the compiler
+   know the value is aligned.  */
 
-static int
-cmp_ext32l_r_offset (const void *p, const void *q)
+static bfd_vma
+ext32l_r_offset (const void *p)
 {
   union aligned32
   {
@@ -8113,27 +8115,17 @@ cmp_ext32l_r_offset (const void *p, const void *q)
     unsigned char c[4];
   };
   const union aligned32 *a
-    = (const union aligned32 *) ((const Elf32_External_Rel *) p)->r_offset;
-  const union aligned32 *b
-    = (const union aligned32 *) ((const Elf32_External_Rel *) q)->r_offset;
+    = (const union aligned32 *) &((const Elf32_External_Rel *) p)->r_offset;
 
   uint32_t aval = (  (uint32_t) a->c[0]
 		   | (uint32_t) a->c[1] << 8
 		   | (uint32_t) a->c[2] << 16
 		   | (uint32_t) a->c[3] << 24);
-  uint32_t bval = (  (uint32_t) b->c[0]
-		   | (uint32_t) b->c[1] << 8
-		   | (uint32_t) b->c[2] << 16
-		   | (uint32_t) b->c[3] << 24);
-  if (aval < bval)
-    return -1;
-  else if (aval > bval)
-    return 1;
-  return 0;
+  return aval;
 }
 
-static int
-cmp_ext32b_r_offset (const void *p, const void *q)
+static bfd_vma
+ext32b_r_offset (const void *p)
 {
   union aligned32
   {
@@ -8141,28 +8133,18 @@ cmp_ext32b_r_offset (const void *p, const void *q)
     unsigned char c[4];
   };
   const union aligned32 *a
-    = (const union aligned32 *) ((const Elf32_External_Rel *) p)->r_offset;
-  const union aligned32 *b
-    = (const union aligned32 *) ((const Elf32_External_Rel *) q)->r_offset;
+    = (const union aligned32 *) &((const Elf32_External_Rel *) p)->r_offset;
 
   uint32_t aval = (  (uint32_t) a->c[0] << 24
 		   | (uint32_t) a->c[1] << 16
 		   | (uint32_t) a->c[2] << 8
 		   | (uint32_t) a->c[3]);
-  uint32_t bval = (  (uint32_t) b->c[0] << 24
-		   | (uint32_t) b->c[1] << 16
-		   | (uint32_t) b->c[2] << 8
-		   | (uint32_t) b->c[3]);
-  if (aval < bval)
-    return -1;
-  else if (aval > bval)
-    return 1;
-  return 0;
+  return aval;
 }
 
 #ifdef BFD_HOST_64_BIT
-static int
-cmp_ext64l_r_offset (const void *p, const void *q)
+static bfd_vma
+ext64l_r_offset (const void *p)
 {
   union aligned64
   {
@@ -8170,9 +8152,7 @@ cmp_ext64l_r_offset (const void *p, const void *q)
     unsigned char c[8];
   };
   const union aligned64 *a
-    = (const union aligned64 *) ((const Elf64_External_Rel *) p)->r_offset;
-  const union aligned64 *b
-    = (const union aligned64 *) ((const Elf64_External_Rel *) q)->r_offset;
+    = (const union aligned64 *) &((const Elf64_External_Rel *) p)->r_offset;
 
   uint64_t aval = (  (uint64_t) a->c[0]
 		   | (uint64_t) a->c[1] << 8
@@ -8182,23 +8162,11 @@ cmp_ext64l_r_offset (const void *p, const void *q)
 		   | (uint64_t) a->c[5] << 40
 		   | (uint64_t) a->c[6] << 48
 		   | (uint64_t) a->c[7] << 56);
-  uint64_t bval = (  (uint64_t) b->c[0]
-		   | (uint64_t) b->c[1] << 8
-		   | (uint64_t) b->c[2] << 16
-		   | (uint64_t) b->c[3] << 24
-		   | (uint64_t) b->c[4] << 32
-		   | (uint64_t) b->c[5] << 40
-		   | (uint64_t) b->c[6] << 48
-		   | (uint64_t) b->c[7] << 56);
-  if (aval < bval)
-    return -1;
-  else if (aval > bval)
-    return 1;
-  return 0;
+  return aval;
 }
 
-static int
-cmp_ext64b_r_offset (const void *p, const void *q)
+static bfd_vma
+ext64b_r_offset (const void *p)
 {
   union aligned64
   {
@@ -8206,9 +8174,7 @@ cmp_ext64b_r_offset (const void *p, const void *q)
     unsigned char c[8];
   };
   const union aligned64 *a
-    = (const union aligned64 *) ((const Elf64_External_Rel *) p)->r_offset;
-  const union aligned64 *b
-    = (const union aligned64 *) ((const Elf64_External_Rel *) q)->r_offset;
+    = (const union aligned64 *) &((const Elf64_External_Rel *) p)->r_offset;
 
   uint64_t aval = (  (uint64_t) a->c[0] << 56
 		   | (uint64_t) a->c[1] << 48
@@ -8218,19 +8184,7 @@ cmp_ext64b_r_offset (const void *p, const void *q)
 		   | (uint64_t) a->c[5] << 16
 		   | (uint64_t) a->c[6] << 8
 		   | (uint64_t) a->c[7]);
-  uint64_t bval = (  (uint64_t) b->c[0] << 56
-		   | (uint64_t) b->c[1] << 48
-		   | (uint64_t) b->c[2] << 40
-		   | (uint64_t) b->c[3] << 32
-		   | (uint64_t) b->c[4] << 24
-		   | (uint64_t) b->c[5] << 16
-		   | (uint64_t) b->c[6] << 8
-		   | (uint64_t) b->c[7]);
-  if (aval < bval)
-    return -1;
-  else if (aval > bval)
-    return 1;
-  return 0;
+  return aval;
 }
 #endif
 
@@ -8299,16 +8253,20 @@ elf_link_adjust_relocs (bfd *abfd,
       (*swap_out) (abfd, irela, erela);
     }
 
-  if (sort)
+  if (sort && count != 0)
     {
-      int (*compare) (const void *, const void *);
+      bfd_vma (*ext_r_off) (const void *);
+      bfd_vma r_off;
+      size_t elt_size;
+      bfd_byte *base, *end, *p, *loc;
+      bfd_byte buf[sizeof (Elf64_External_Rela)];
 
       if (bed->s->arch_size == 32)
 	{
 	  if (abfd->xvec->header_byteorder == BFD_ENDIAN_LITTLE)
-	    compare = cmp_ext32l_r_offset;
+	    ext_r_off = ext32l_r_offset;
 	  else if (abfd->xvec->header_byteorder == BFD_ENDIAN_BIG)
-	    compare = cmp_ext32b_r_offset;
+	    ext_r_off = ext32b_r_offset;
 	  else
 	    abort ();
 	}
@@ -8316,14 +8274,61 @@ elf_link_adjust_relocs (bfd *abfd,
 	{
 #ifdef BFD_HOST_64_BIT
 	  if (abfd->xvec->header_byteorder == BFD_ENDIAN_LITTLE)
-	    compare = cmp_ext64l_r_offset;
+	    ext_r_off = ext64l_r_offset;
 	  else if (abfd->xvec->header_byteorder == BFD_ENDIAN_BIG)
-	    compare = cmp_ext64b_r_offset;
+	    ext_r_off = ext64b_r_offset;
 	  else
 #endif
 	    abort ();
 	}
-      qsort (reldata->hdr->contents, count, reldata->hdr->sh_entsize, compare);
+
+      /*  Must use a stable sort here.  Insertion sort, since the
+	  relocs are mostly sorted already.  */
+      elt_size = reldata->hdr->sh_entsize;
+      base = reldata->hdr->contents;
+      end = base + count * elt_size;
+      if (elt_size > sizeof (buf))
+	abort ();
+
+      /* Ensure the first element is lowest.  This acts as a sentinel,
+	 speeding the main loop below.  */
+      r_off = (*ext_r_off) (base);
+      for (p = loc = base; (p += elt_size) < end; )
+	{
+	  bfd_vma r_off2 = (*ext_r_off) (p);
+	  if (r_off > r_off2)
+	    {
+	      r_off = r_off2;
+	      loc = p;
+	    }
+	}
+      if (loc != base)
+	{
+	  /* Don't just swap *base and *loc as that changes the order
+	     of the original base[0] and base[1] if they happen to
+	     have the same r_offset.  */
+	  memcpy (buf, loc, elt_size);
+	  memmove (base + elt_size, base, loc - base);
+	  memcpy (base, buf, elt_size);
+	}
+
+      for (p = base + elt_size; (p += elt_size) < end; )
+	{
+	  /* base to p is sorted, *p is next to insert.  */
+	  r_off = (*ext_r_off) (p);
+	  /* Search the sorted region for location to insert.  */
+	  loc = p - elt_size;
+	  while (r_off < (*ext_r_off) (loc))
+	    loc -= elt_size;
+	  loc += elt_size;
+	  if (loc != p)
+	    {
+	      memcpy (buf, p, elt_size);
+	      memmove (loc + elt_size, loc, p - loc);
+	      memcpy (loc, buf, elt_size);
+	    }
+	}
+      /* Hashes are no longer valid.  */
       free (reldata->hashes);
       reldata->hashes = NULL;
     }