Hi!

libtsan only handles the standard memory model values, so I've added
just in case some new unknown memory model is used bail outs (keeping
the __atomic_* builtins instead of transforming them to __tsan_atomic*).
Except that at -O0 (or if unlucky enough otherwise) if the memory model
is variable, that means we never use __tsan_atomic*, which means libtsan
reports false positive races.  We could do those checks at runtime by
performing if ((last_arg & 0x7fff) >= 6) __atomic_* else __tsan_atomic_*,
but as there are no such values yet I think it isn't worth it (the
sync/hle acq/hle rel bits which are ored are 0x8000, 0x10000 and 0x20000
and memmodel_base strips them off).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-03-20  Jakub Jelinek  <ja...@redhat.com>

        PR sanitizer/78158
        * tsan.c (instrument_builtin_call): If the memory model argument
        is not a constant, assume it is valid.

--- gcc/tsan.c.jj       2017-01-01 12:45:38.000000000 +0100
+++ gcc/tsan.c  2017-03-20 17:55:25.509294018 +0100
@@ -499,8 +499,8 @@ instrument_builtin_call (gimple_stmt_ite
          case check_last:
          case fetch_op:
            last_arg = gimple_call_arg (stmt, num - 1);
-           if (!tree_fits_uhwi_p (last_arg)
-               || memmodel_base (tree_to_uhwi (last_arg)) >= MEMMODEL_LAST)
+           if (tree_fits_uhwi_p (last_arg)
+               && memmodel_base (tree_to_uhwi (last_arg)) >= MEMMODEL_LAST)
              return;
            gimple_call_set_fndecl (stmt, decl);
            update_stmt (stmt);
@@ -564,11 +564,11 @@ instrument_builtin_call (gimple_stmt_ite
            gcc_assert (num == 6);
            for (j = 0; j < 6; j++)
              args[j] = gimple_call_arg (stmt, j);
-           if (!tree_fits_uhwi_p (args[4])
-               || memmodel_base (tree_to_uhwi (args[4])) >= MEMMODEL_LAST)
+           if (tree_fits_uhwi_p (args[4])
+               && memmodel_base (tree_to_uhwi (args[4])) >= MEMMODEL_LAST)
              return;
-           if (!tree_fits_uhwi_p (args[5])
-               || memmodel_base (tree_to_uhwi (args[5])) >= MEMMODEL_LAST)
+           if (tree_fits_uhwi_p (args[5])
+               && memmodel_base (tree_to_uhwi (args[5])) >= MEMMODEL_LAST)
              return;
            update_gimple_call (gsi, decl, 5, args[0], args[1], args[2],
                                args[4], args[5]);
@@ -642,8 +642,8 @@ instrument_builtin_call (gimple_stmt_ite
                  return;
              }
            last_arg = gimple_call_arg (stmt, num - 1);
-           if (!tree_fits_uhwi_p (last_arg)
-               || memmodel_base (tree_to_uhwi (last_arg)) >= MEMMODEL_LAST)
+           if (tree_fits_uhwi_p (last_arg)
+               && memmodel_base (tree_to_uhwi (last_arg)) >= MEMMODEL_LAST)
              return;
            t = TYPE_ARG_TYPES (TREE_TYPE (decl));
            t = TREE_VALUE (TREE_CHAIN (t));

        Jakub

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