Make SRA scalarize constant-pool loads

Make SRA scalarize constant-pool loads

PR target/63679

gcc/ChangeLog:

	* tree-sra.c (disqualified_constants, constant_decl_p): New.
	(sra_initialize): Allocate disqualified_constants.
	(sra_deinitialize): Free disqualified_constants.
	(disqualify_candidate): Update disqualified_constants when appropriate.
	(create_access): Scan for constant-pool entries as we go along.
	(scalarizable_type_p): Add check against type_contains_placeholder_p.
	(maybe_add_sra_candidate): Allow constant-pool entries.
	(load_assign_lhs_subreplacements): Bind debug for constant pool vars.
	(initialize_constant_pool_replacements): New.
	(sra_modify_assign): Avoid mangling assignments created by previous,
	and don't generate writes into constant pool.
	(sra_modify_function_body): Call initialize_constant_pool_replacements.

gcc/testsuite/:

	* gcc.dg/tree-ssa/sra-17.c: New.
	* gcc.dg/tree-ssa/sra-18.c: New.

From-SVN: r232506