[GOOGLE] Workaround a bug in AutoFDO which may leads to infinite loop for inlined assembly

[Dehao Chen]

This patch fixed a bug in getting inline stacks: if there is no
location info attached to a block, we should *not* try to get its
function name because it could result in infinite loop.

Bootstrapped and passed all regression tests.

Ok for gcc-4_7 branch?

Thanks,
Dehao

Index: gcc/auto-profile.c
===================================================================
--- gcc/auto-profile.c (revision 198117)
+++ gcc/auto-profile.c (working copy)
@@ -662,9 +662,10 @@ get_inline_stack_by_stmt (gimple stmt, tree decl,
        block && (TREE_CODE (block) == BLOCK);
        block = BLOCK_SUPERCONTEXT (block))
     {
-      tree decl = get_function_decl_from_block (block);
+      tree decl;
       if (LOCATION_LOCUS (BLOCK_SOURCE_LOCATION (block)) == UNKNOWN_LOCATION)
  continue;
+      decl = get_function_decl_from_block (block);
       loc = BLOCK_SOURCE_LOCATION (block);
       pos_stack[idx].file = expand_location (loc).file;
       pos_stack[idx].line = expand_location (loc).line;