PR other/69554: avoid excessive source printing for widely-separated locations

PR other/69554: avoid excessive source printing for widely-separated locations

gcc/ChangeLog:
	PR other/69554
	* diagnostic-show-locus.c (struct line_span): New struct.
	(layout::get_first_line): Delete.
	(layout::get_last_line): Delete.
	(layout::get_num_line_spans): New member function.
	(layout::get_line_span): Likewise.
	(layout::print_heading_for_line_span_index_p): Likewise.
	(layout::get_expanded_location): Likewise.
	(layout::calculate_line_spans): Likewise.
	(layout::m_first_line): Delete.
	(layout::m_last_line): Delete.
	(layout::m_line_spans): New field.
	(layout::layout): Update comment.  Replace m_first_line and
	m_last_line with m_line_spans, replacing their initialization
	with a call to calculate_line_spans.
	(diagnostic_show_locus): When printing source lines and
	annotations, rather than looping over a single span
	of lines, instead loop over each line_span within
	the layout, with an inner loop over the lines within them.
	Call the context's start_span callback when changing line spans.
	* diagnostic.c (diagnostic_initialize): Initialize start_span.
	(diagnostic_build_prefix): Break out the building of the location
	part of the string into...
	(diagnostic_get_location_text): ...this new function, rewriting
	it from nested ternary expressions to a sequence of "if"
	statements.
	(default_diagnostic_start_span_fn): New function.
	* diagnostic.h (diagnostic_start_span_fn): New typedef.
	(diagnostic_context::start_span): New field.
	(default_diagnostic_start_span_fn): New prototype.

gcc/fortran/ChangeLog:
	PR other/69554
	* error.c (gfc_diagnostic_start_span): New function.
	(gfc_diagnostics_init): Initialize global_dc's start_span.

gcc/testsuite/ChangeLog:
	PR other/69554
	* gcc.dg/pr69554-1.c: New test.
	* gfortran.dg/pr69554-1.F90: New test.
	* gfortran.dg/pr69554-2.F90: New test.
	* lib/gcc-dg.exp (proc dg-locus): New function.
	* lib/gfortran-dg.exp (proc gfortran-dg-test): Update comment to
	distinguish between the caret-printing and non-caret-printing
	cases.  If caret-printing has been explicitly enabled, bail out
	without attempting to fix up the output.

From-SVN: r233386