Extend modref by side-effect analysis
Make modref to also collect info whether function has side
effects. This allows pure/const function detection and also handling
functions which do store some memory in similar way as we handle
pure/consts now.
The code is symmetric to what ipa-pure-const does. Modref is actually more
capable on proving that a given function is pure/const (since it understands
that non-pure function can be called when it only modifies data on stack)
so we could retire ipa-pure-const's pure-const discovery at some point.
However this patch only does the anlaysis - the consumers of this flag
will come next.
Bootstrapped/regtested x86_64-linux. I plan to commit it later today
if there are no complains.
gcc/ChangeLog:
* ipa-modref.c: Include tree-eh.h
(modref_summary::modref_summary): Initialize side_effects.
(struct modref_summary_lto): New bool field side_effects.
(modref_summary_lto::modref_summary_lto): Initialize side_effects.
(modref_summary::dump): Dump side_effects.
(modref_summary_lto::dump): Dump side_effects.
(merge_call_side_effects): Merge side effects.
(process_fnspec): Calls to non-const/pure or looping
function is a side effect.
(analyze_call): Self-recursion is a side-effect; handle
special builtins.
(analyze_load): Watch for volatile and throwing memory.
(analyze_store): Likewise.
(analyze_stmt): Watch for volatitle asm.
(analyze_function): Handle side_effects.
(modref_summaries::duplicate): Duplicate side_effects.
(modref_summaries_lto::duplicate): Likewise.
(modref_write): Stream side_effects.
(read_section): Likewise.
(update_signature): Update.
(propagate_unknown_call): Handle side_effects.
(modref_propagate_in_scc): Likewise.
* ipa-modref.h (struct modref_summary): Add side_effects.
* ipa-pure-const.c (special_builtin_state): Rename to ...
(builtin_safe_for_const_function_p): ... this one.
(check_call): Update.
(finite_function_p): Break out from ...
(propagate_pure_const): ... here
* ipa-utils.h (finite_function): Declare.