Hi,
in firefox .optimized dumps one can see few places where __builtin_unreachable
is called (as a result of devirtualization code proving the code path to be
undefined). There is usually some argument setup for the parameters of
__builtin_unreachable that are dead. This patch makes it somewhat better
so now we get:
<bb 30>:
# prephitmp_222 = PHI <_52(27), pretmp_245(29)>
_57 = prephitmp_222 + 2;
pool_40(D)->ptr = _57;
__builtin_unreachable ();
Why DSE does not eliminate the stores prior noreturn const function?
Bootstrapped/regtested x86_64-linux, OK?
Honza
* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Remove dead
parameters
of BUILT_IN_UNREACHABLE
Index: tree-ssa-dce.c
===================================================================
--- tree-ssa-dce.c (revision 218610)
+++ tree-ssa-dce.c (working copy)
@@ -250,6 +250,15 @@ mark_stmt_if_obviously_necessary (gimple
case BUILT_IN_ALLOCA:
case BUILT_IN_ALLOCA_WITH_ALIGN:
return;
+ case BUILT_IN_UNREACHABLE:
+ /* All parameters of BUILT_IN_UNREACHABLE are dead. Remove them
+ from the stmt, so we can remove their definitions. */
+ if (gimple_call_num_args (stmt))
+ {
+ gimple_set_num_ops (stmt, 3);
+ update_stmt (stmt);
+ }
+ break;
default:;
}
