[riscv] avoid auipc overflow with large offsets [PR91420]

[riscv] avoid auipc overflow with large offsets [PR91420]

When computing an address plus a large offset on riscv64 with a
PC-relative sequence, we may hit the range limit for auipc and get a
relocation overflow, where on riscv32 the computation wraps around.

Since -mcmodel=medany requires the entire program to fit in a 2GiB
address range, a +/-1GiB+ offset added to an in-range symbol in a
barely-fitting program is more likely than not to be out-of-range.
Since such large constants are unlikely to come up by chance, separate
them from the symbol so as to avoid the relocation overflow.

for  gcc/ChangeLog

	PR target/91420
	* config/riscv/riscv.cc (riscv_symbolic_constant_p): Require
	offsets smaller than +/- 1GiB for PCREL symbols.

for  gcc/testsuite/ChangeLog

	PR target/91420
	* gcc.target/riscv/pr91420.c: New.