diff options
Diffstat (limited to 'gcc/symtab.c')
| -rw-r--r-- | gcc/symtab.c | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/gcc/symtab.c b/gcc/symtab.c index deb317d1fb3..3a59935d132 100644 --- a/gcc/symtab.c +++ b/gcc/symtab.c @@ -1890,4 +1890,67 @@ symtab_get_symbol_partitioning_class (symtab_node *node) return SYMBOL_PARTITION; } + +/* Return true when symbol is known to be non-zero. */ + +bool +symtab_node::nonzero_address () +{ + /* Weakrefs may be NULL when their target is not defined. */ + if (this->alias && this->weakref) + { + if (this->analyzed) + { + symtab_node *target = symtab_alias_ultimate_target (this); + + if (target->alias && target->weakref) + return false; + /* We can not recurse to target::nonzero. It is possible that the + target is used only via the alias. + We may walk references and look for strong use, but we do not know + if this strong use will survive to final binary, so be + conservative here. + ??? Maybe we could do the lookup during late optimization that + could be useful to eliminate the NULL pointer checks in LTO + programs. */ + if (target->definition && !DECL_EXTERNAL (target->decl)) + return true; + if (target->resolution != LDPR_UNKNOWN + && target->resolution != LDPR_UNDEF + && flag_delete_null_pointer_checks) + return true; + return false; + } + else + return false; + } + + /* With !flag_delete_null_pointer_checks we assume that symbols may + bind to NULL. This is on by default on embedded targets only. + + Otherwise all non-WEAK symbols must be defined and thus non-NULL or + linking fails. Important case of WEAK we want to do well are comdats. + Those are handled by later check for definition. + + When parsing, beware the cases when WEAK attribute is added later. */ + if (!DECL_WEAK (this->decl) + && flag_delete_null_pointer_checks + && cgraph_state > CGRAPH_STATE_PARSING) + return true; + + /* If target is defined and not extern, we know it will be output and thus + it will bind to non-NULL. + Play safe for flag_delete_null_pointer_checks where weak definition maye + be re-defined by NULL. */ + if (this->definition && !DECL_EXTERNAL (this->decl) + && (flag_delete_null_pointer_checks || !DECL_WEAK (this->decl))) + return true; + + /* As the last resort, check the resolution info. */ + if (this->resolution != LDPR_UNKNOWN + && this->resolution != LDPR_UNDEF + && flag_delete_null_pointer_checks) + return true; + return false; +} #include "gt-symtab.h" |