i386: Access external function via GOT slot for -fno-plt

i386: Access external function via GOT slot for -fno-plt

i386 psABI has been updated to clarify that R_386_GOT32X and R_386_GOT32
relocations can be used to access GOT without base register when PIC is
disabled:

https://groups.google.com/forum/#!topic/ia32-abi/awsRSvJOJfs

32-bit x86 assembler and linker from binutils 2.26.1 and 2.27 support

call/jmp *_start@GOT
cmpl $0, bar@GOT

for both normal and IFUNC functions.  We check if 32-bit x86 assembler
and linker have the fix for:

https://sourceware.org/bugzilla/show_bug.cgi?id=20244

before accessing external function via GOT slot for -fno-plt in both PIC
and non-PIC modes.

	PR target/66232
	PR target/67400
	* configure.ac (as_ix86_tls_ldm_opt): Renamed to ...
	(as_ix86_gas_32_opt): This.
	(ld_ix86_tls_ldm_opt): Renamed to ...
	(ld_ix86_gld_32_opt): This.
	(R_386_TLS_LDM reloc): Updated.
	(R_386_GOT32X reloc): New assembler/linker check.
	(HAVE_AS_IX86_GOT32X): New.  Defined to 1 if 32-bit assembler and
	linker support "jmp *_start@GOT" and "cmpl $0, bar@GOT".  Otherise,
	defined to 0.
	* config.in: Regenerated.
	* configure: Likewise.
	* config/i386/i386.c (ix86_force_load_from_GOT_p): Return
	true if HAVE_AS_IX86_GOT32X is 1 in 32-bit mode.
	(ix86_legitimate_address_p): Allow UNSPEC_GOT for -fno-plt
	if ix86_force_load_from_GOT_p returns true.
	(ix86_print_operand_address_as): Also support UNSPEC_GOT if
	ix86_force_load_from_GOT_p returns true.
	(ix86_expand_move): Generate UNSPEC_GOT in 32-bit mode to load
	the external function address via the GOT slot.
	(ix86_nopic_noplt_attribute_p): Check both TARGET_64BIT and
	HAVE_AS_IX86_GOT32X before returning false.
	(ix86_output_call_insn): Generate "%!jmp/call\t*%p0@GOT" in
	32-bit mode if ix86_nopic_noplt_attribute_p returns true.

gcc/testsuite/

	PR target/66232
	PR target/67400
	* gcc.target/i386/pr66232-14.c: New file.
	* gcc.target/i386/pr66232-15.c: Likewise.
	* gcc.target/i386/pr66232-16.c: Likewise.
	* gcc.target/i386/pr66232-17.c: Likewise.
	* gcc.target/i386/pr67400-1.c: Don't disable for ia32.  Scan for
	ia32 if R_386_GOT32X relocation is supported.
	* gcc.target/i386/pr67400-2.c: Likewise.
	* gcc.target/i386/pr67400-3.c: Likewise.
	* gcc.target/i386/pr67400-4.c: Likewise.
	* gcc.target/i386/pr67400-6.c: Likewise.
	* gcc.target/i386/pr67400-7.c: Likewise.
	* lib/target-supports.exp (check_effective_target_got32x_reloc):
	New.

From-SVN: r237736