[PATCH] Fix PR gcov-profile/55734 for bootstrapping with older compilers (issue6980044)

[Teresa Johnson]

Fix PR gcov-profile/55734 by using methods from hwint.c instead of
builtins, to handle non-GCC and older versions of GCC. When building
libgcov.a, however, hwint.c is not available, but we are always using
the bootstrapped compiler and can therefore use the builtins.

Use __builtin_popcount instead of __builtin_popcountll, since we
are operating on an int.

Use floor_log2 directly, instead of clz_hwi for the non-libgcov case,
and handle situations where the size of the gcov_type is bigger than
HOST_WIDE_INT. Verified that the various cases compiled by forcing
different HOST_BITS_PER_WIDE_INT values.

Bootstrapped and tested on x86_64-unknown-linux-gnu. Ok for trunk?

Thanks,
Teresa

2012-12-19  Teresa Johnson  <tejohnson@google.com>
            Jakub Jelinek  <jakub@redhat.com>

        PR gcov-profile/55734
	* gcov-io.c (gcov_read_summary): Use __builtin_popcount instead
        of __builtin_popcountll when building libgcov.a, otherwise use
        popcount_hwi.
	(gcov_histo_index): When not building libgcov.a, use floor_log2
        instead of __builtin_clzll.

Index: gcov-io.c
===================================================================
--- gcov-io.c	(revision 194585)
+++ gcov-io.c	(working copy)
@@ -538,7 +538,15 @@ gcov_read_summary (struct gcov_summary *summary)
       for (bv_ix = 0; bv_ix < GCOV_HISTOGRAM_BITVECTOR_SIZE; bv_ix++)
         {
           histo_bitvector[bv_ix] = gcov_read_unsigned ();
-          h_cnt += __builtin_popcountll (histo_bitvector[bv_ix]);
+#if IN_LIBGCOV
+          /* When building libgcov we don't include system.h, which includes
+             hwint.h (where popcount_hwi is declared). However, libgcov.a
+             is built by the bootstrapped compiler and therefore the builtins
+             are always available.  */
+          h_cnt += __builtin_popcount (histo_bitvector[bv_ix]);
+#else
+          h_cnt += popcount_hwi (histo_bitvector[bv_ix]);
+#endif
         }
       bv_ix = 0;
       h_ix = 0;
@@ -642,7 +650,33 @@ gcov_histo_index (gcov_type value)
 
   /* Find the place of the most-significant bit set.  */
   if (v > 0)
-    r = 63 - __builtin_clzll (v);
+    {
+#if IN_LIBGCOV
+      /* When building libgcov we don't include system.h, which includes
+         hwint.h (where floor_log2 is declared). However, libgcov.a
+         is built by the bootstrapped compiler and therefore the builtins
+         are always available.  */
+      r = 63 - __builtin_clzll (v);
+#else
+      /* We use floor_log2 from hwint.c, which takes a HOST_WIDE_INT
+         that is either 32 or 64 bits, and gcov_type_unsigned may be 64 bits.
+         Need to check for the case where gcov_type_unsigned is 64 bits
+         and HOST_WIDE_INT is 32 bits and handle it specially.  */
+#if LONG_LONG_TYPE_SIZE <= HOST_BITS_PER_WIDE_INT
+      r = floor_log2 (v);
+#else
+#if LONG_LONG_TYPE_SIZE == 2 * HOST_BITS_PER_WIDE_INT
+      HOST_WIDE_INT hwi_v = v >> HOST_BITS_PER_WIDE_INT;
+      if (hwi_v)
+        r = floor_log2 (hwi_v) + HOST_BITS_PER_WIDE_INT;
+      else
+        r = floor_log2 ((HOST_WIDE_INT)v);
+#else
+      gcc_unreachable ();
+#endif
+#endif
+#endif
+    }
 
   /* If at most the 2 least significant bits are set (value is
      0 - 3) then that value is our index into the lowest set of

--
This patch is available for review at http://codereview.appspot.com/6980044