Faster string merging

* use power-of-two hash table
* use better hash function (hashing 32bits at once and with better
  mixing characteristics)
* use input-offset-to-entry maps instead of retaining full input
  contents for lookup time
* don't reread SEC_MERGE section multiple times
* care for cache behaviour for the hot lookup routine

The overall effect is less usage in libz and much faster string merging
itself.  On a debug-info-enabled cc1 the effect at the time of this
writing on the machine I used was going from 14400 perf samples to 9300
perf samples or from 3.7 seconds to 2.4 seconds, i.e. about 33% .

bfd/config.in

@@ -7,6 +7,9 @@
 #endif
 #define __CONFIG_H__ 1
 
+/* Define if building universal (internal helper macro) */
+#undef AC_APPLE_UNIVERSAL_BUILD
+
 /* Name of host specific core header file to include in elf.c. */
 #undef CORE_HEADER
 
@@ -325,6 +328,18 @@
 /* Version number of package */
 #undef VERSION
 
+/* Define WORDS_BIGENDIAN to 1 if your processor stores words with the most
+   significant byte first (like Motorola and SPARC, unlike Intel). */
+#if defined AC_APPLE_UNIVERSAL_BUILD
+# if defined __BIG_ENDIAN__
+#  define WORDS_BIGENDIAN 1
+# endif
+#else
+# ifndef WORDS_BIGENDIAN
+#  undef WORDS_BIGENDIAN
+# endif
+#endif
+
 /* Enable large inode numbers on Mac OS X 10.5.  */
 #ifndef _DARWIN_USE_64_BIT_INODE
 # define _DARWIN_USE_64_BIT_INODE 1

bfd/configure

@@ -12349,6 +12349,231 @@ fi
 
 
 
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether byte ordering is bigendian" >&5
+$as_echo_n "checking whether byte ordering is bigendian... " >&6; }
+if ${ac_cv_c_bigendian+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_cv_c_bigendian=unknown
+    # See if we're dealing with a universal compiler.
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#ifndef __APPLE_CC__
+	       not a universal capable compiler
+	     #endif
+	     typedef int dummy;
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+
+	# Check for potential -arch flags.  It is not universal unless
+	# there are at least two -arch flags with different values.
+	ac_arch=
+	ac_prev=
+	for ac_word in $CC $CFLAGS $CPPFLAGS $LDFLAGS; do
+	 if test -n "$ac_prev"; then
+	   case $ac_word in
+	     i?86 | x86_64 | ppc | ppc64)
+	       if test -z "$ac_arch" || test "$ac_arch" = "$ac_word"; then
+		 ac_arch=$ac_word
+	       else
+		 ac_cv_c_bigendian=universal
+		 break
+	       fi
+	       ;;
+	   esac
+	   ac_prev=
+	 elif test "x$ac_word" = "x-arch"; then
+	   ac_prev=arch
+	 fi
+       done
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+    if test $ac_cv_c_bigendian = unknown; then
+      # See if sys/param.h defines the BYTE_ORDER macro.
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <sys/types.h>
+	     #include <sys/param.h>
+
+int
+main ()
+{
+#if ! (defined BYTE_ORDER && defined BIG_ENDIAN \
+		     && defined LITTLE_ENDIAN && BYTE_ORDER && BIG_ENDIAN \
+		     && LITTLE_ENDIAN)
+	      bogus endian macros
+	     #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  # It does; now see whether it defined to BIG_ENDIAN or not.
+	 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <sys/types.h>
+		#include <sys/param.h>
+
+int
+main ()
+{
+#if BYTE_ORDER != BIG_ENDIAN
+		 not big endian
+		#endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ac_cv_c_bigendian=yes
+else
+  ac_cv_c_bigendian=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+    fi
+    if test $ac_cv_c_bigendian = unknown; then
+      # See if <limits.h> defines _LITTLE_ENDIAN or _BIG_ENDIAN (e.g., Solaris).
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <limits.h>
+
+int
+main ()
+{
+#if ! (defined _LITTLE_ENDIAN || defined _BIG_ENDIAN)
+	      bogus endian macros
+	     #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  # It does; now see whether it defined to _BIG_ENDIAN or not.
+	 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <limits.h>
+
+int
+main ()
+{
+#ifndef _BIG_ENDIAN
+		 not big endian
+		#endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ac_cv_c_bigendian=yes
+else
+  ac_cv_c_bigendian=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+    fi
+    if test $ac_cv_c_bigendian = unknown; then
+      # Compile a test program.
+      if test "$cross_compiling" = yes; then :
+  # Try to guess by grepping values from an object file.
+	 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+short int ascii_mm[] =
+		  { 0x4249, 0x4765, 0x6E44, 0x6961, 0x6E53, 0x7953, 0 };
+		short int ascii_ii[] =
+		  { 0x694C, 0x5454, 0x656C, 0x6E45, 0x6944, 0x6E61, 0 };
+		int use_ascii (int i) {
+		  return ascii_mm[i] + ascii_ii[i];
+		}
+		short int ebcdic_ii[] =
+		  { 0x89D3, 0xE3E3, 0x8593, 0x95C5, 0x89C4, 0x9581, 0 };
+		short int ebcdic_mm[] =
+		  { 0xC2C9, 0xC785, 0x95C4, 0x8981, 0x95E2, 0xA8E2, 0 };
+		int use_ebcdic (int i) {
+		  return ebcdic_mm[i] + ebcdic_ii[i];
+		}
+		extern int foo;
+
+int
+main ()
+{
+return use_ascii (foo) == use_ebcdic (foo);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  if grep BIGenDianSyS conftest.$ac_objext >/dev/null; then
+	      ac_cv_c_bigendian=yes
+	    fi
+	    if grep LiTTleEnDian conftest.$ac_objext >/dev/null ; then
+	      if test "$ac_cv_c_bigendian" = unknown; then
+		ac_cv_c_bigendian=no
+	      else
+		# finding both strings is unlikely to happen, but who knows?
+		ac_cv_c_bigendian=unknown
+	      fi
+	    fi
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+$ac_includes_default
+int
+main ()
+{
+
+	     /* Are we little or big endian?  From Harbison&Steele.  */
+	     union
+	     {
+	       long int l;
+	       char c[sizeof (long int)];
+	     } u;
+	     u.l = 1;
+	     return u.c[sizeof (long int) - 1] == 1;
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_run "$LINENO"; then :
+  ac_cv_c_bigendian=no
+else
+  ac_cv_c_bigendian=yes
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
+  conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+
+    fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_bigendian" >&5
+$as_echo "$ac_cv_c_bigendian" >&6; }
+ case $ac_cv_c_bigendian in #(
+   yes)
+     $as_echo "#define WORDS_BIGENDIAN 1" >>confdefs.h
+;; #(
+   no)
+      ;; #(
+   universal)
+
+$as_echo "#define AC_APPLE_UNIVERSAL_BUILD 1" >>confdefs.h
+
+     ;; #(
+   *)
+     as_fn_error $? "unknown endianness
+ presetting ac_cv_c_bigendian=no (or yes) will help" "$LINENO" 5 ;;
+ esac
+
+
 host64=false
 target64=false
 bfd_default_target_size=32
@@ -15481,6 +15706,7 @@ if test -z "${INSTALL_LIBBFD_TRUE}" && test -z "${INSTALL_LIBBFD_FALSE}"; then
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
 
+
 : "${CONFIG_STATUS=./config.status}"
 ac_write_fail=0
 ac_clean_files_save=$ac_clean_files

bfd/configure.ac

@@ -193,6 +193,8 @@ AM_CONDITIONAL(GENINSRC_NEVER, false)
 AM_INSTALL_LIBBFD
 AC_EXEEXT
 
+AC_C_BIGENDIAN
+
 host64=false
 target64=false
 bfd_default_target_size=32

bfd/elflink.c

@@ -11361,6 +11361,13 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd)
 	      contents = flinfo->contents;
 	    }
 	}
+      else if (!(o->flags & SEC_RELOC)
+	       && !bed->elf_backend_write_section
+	       && o->sec_info_type == SEC_INFO_TYPE_MERGE)
+	/* A MERGE section that has no relocations doesn't need the
+	   contents anymore, they have been recorded earlier.  Except
+	   if the backend has special provisions for writing sections.  */
+	contents = NULL;
       else
 	{
 	  contents = flinfo->contents;