The following adds a --param to limit the depth of unswitched loop
nests. One can use --param max-unswitch-depth=1 to disable unswitching
of outer loops (the innermost loop will then be unswitched).
PR tree-optimization/107946
* params.opt (-param=max-unswitch-depth=): New.
* doc/invoke.texi (--param=max-unswitch-depth): Document.
* tree-ssa-loop-unswitch.cc (init_loop_unswitch_info): Honor
--param=max-unswitch-depth
@item max-unswitch-insns
The maximum number of insns of an unswitched loop.
+@item max-unswitch-depth
+The maximum depth of a loop nest to be unswitched.
+
@item lim-expensive
The minimum cost of an expensive expression in the loop invariant motion.
Common Joined UInteger Var(param_max_unswitch_insns) Init(50) Param Optimization
The maximum number of insns of an unswitched loop.
+-param=max-unswitch-depth=
+Common Joined UInteger Var(param_max_unswitch_depth) Init(50) IntegerRange(1, 50) Param Optimization
+The maximum depth of a loop nest to be unswitched.
+
-param=max-variable-expansions-in-unroller=
Common Joined UInteger Var(param_max_variable_expansions) Init(1) Param Optimization
If -fvariable-expansion-in-unroller is used, the maximum number of times that an individual variable will be expanded during loop unrolling.
/* Unswitch only nests with no sibling loops. */
class loop *outer_loop = loop;
+ unsigned max_depth = param_max_unswitch_depth;
while (loop_outer (outer_loop)->num != 0
- && !loop_outer (outer_loop)->inner->next)
+ && !loop_outer (outer_loop)->inner->next
+ && --max_depth != 0)
outer_loop = loop_outer (outer_loop);
hottest = NULL;
hottest_bb = NULL;