ipa-sra: Be optimistic about Fortran descriptors

ipa-sra: Be optimistic about Fortran descriptors

Fortran descriptors are structures which are often constructed just
for a particular argument of a particular call where it is passed by
reference.  When the called function is under compiler's control, it
can be beneficial to split up the descriptor and pass it in individual
parameters.  Unfortunately, currently we allow IPA-SRA to replace a
pointer with a set of replacements which are at most twice as big in
total and for descriptors we'd need to bump that factor to seven.

This patch looks for parameters which are ADDR_EXPRs of local
variables which are written to and passed as arguments by reference
but are never loaded from and marks them with a flag in the call edge
summary.  The IPA analysis phase then identifies formal parameters
which are always fed such arguments and then is more lenient when it
comoes to size.

In order not to store to maximums per formal parameter, I calculate
the more lenient one by multiplying the existing one with a new
parameter.  If it is preferable to keep the maximums independent, we
can do that.  Documentation for the new parameter is missing as I
still need to re-base the patch on a version which has sphinx.  I will
write it before committing.

I have disable IPA-SRA in pr48636-2.f90 in order to be able to keep
using its dump-scan expressions.  The new testcase is basically a copy
of it with different options and IPA-SRA dump scans.

gcc/ChangeLog:

2022-11-11  Martin Jambor  <mjambor@suse.cz>

	* ipa-sra.cc (isra_param_desc): New field not_specially_constructed.
	(struct isra_param_flow): New field constructed_for_calls.
	(isra_call_summary::dump): Dump the new flag.
	(loaded_decls): New variable.
	(dump_isra_param_descriptor): New parameter hints, dump
	not_specially_constructed if it is true.
	(dump_isra_param_descriptors): New parameter hints, pass it to
	dump_isra_param_descriptor.
	(ipa_sra_function_summaries::duplicate): Duplicate new flag.
	(create_parameter_descriptors): Adjust comment.
	(get_gensum_param_desc): Bail out when decl2desc is NULL.
	(scan_expr_access): Add loaded local variables to loaded_decls.
	(scan_function): Survive if final_bbs is NULL.
	(isra_analyze_call): Compute constructed_for_calls flag.
	(process_scan_results): Be optimistic about size limits.  Do not dump
	computed param hints when dumpint IPA-SRA structures.
	(isra_write_edge_summary): Stream constructed_for_calls.
	(isra_read_edge_summary): Likewise.
	(ipa_sra_dump_all_summaries): New parameter hints, pass it to
	dump_isra_param_descriptor.
	(flip_all_hints_pessimistic): New function.
	(flip_all_param_hints_pessimistic): Likewise.
	(propagate_param_hints): Likewise.
	(disable_unavailable_parameters): Renamed to
	adjust_parameter_descriptions.  Expand size limits for parameters
	which are specially contstructed by all callers.  Check limits again.p
	(ipa_sra_analysis): Pass required hints to ipa_sra_dump_all_summaries.
	Add hint propagation.
	(ipa_sra_summarize_function): Initialize and destory loaded_decls,
	rearrange so that scan_function is called even when there are no
	candidates.
	* params.opt (ipa-sra-ptrwrap-growth-factor): New parameter.

gcc/testsuite/ChangeLog:

2021-11-11  Martin Jambor  <mjambor@suse.cz>

	* gfortran.dg/pr48636-2.f90: Disable IPA-SRA.
	* gfortran.dg/ipa-sra-1.f90: New test.