i386: Allow -mlarge-data-threshold with -mcmodel=large

i386: Allow -mlarge-data-threshold with -mcmodel=large

From: Fangrui Song <maskray@google.com>

When using -mcmodel=medium, large data objects larger than the
-mlarge-data-threshold threshold are placed into large data sections
(.lrodata, .ldata, .lbss and some variants).  GNU ld and ld.lld 17 place
.l* sections into separate output sections.  If small and medium code
model object files are mixed, the .l* sections won't exert relocation
overflow pressure on sections in object files built with -mcmodel=small.

However, when using -mcmodel=large, -mlarge-data-threshold doesn't
apply.  This means that the .rodata/.data/.bss sections may exert
relocation overflow pressure on sections in -mcmodel=small object files.

This patch allows -mcmodel=large to generate .l* sections and drops an
unneeded documentation restriction that the value must be the same.

Link: https://groups.google.com/g/x86-64-abi/c/jnQdJeabxiU
("Large data sections for the large code model")

Signed-off-by: Fangrui Song <maskray@google.com>
gcc/ChangeLog:

	* config/i386/i386.cc (ix86_can_inline_p):
	Handle CM_LARGE and CM_LARGE_PIC.
	(x86_elf_aligned_decl_common): Ditto.
	(x86_output_aligned_bss): Ditto.
	* config/i386/i386.opt: Update doc for -mlarge-data-threshold=.
	* doc/invoke.texi: Update doc for -mlarge-data-threshold=.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/large-data.c: New test.