This fixes PR82964 which reports ICEs for some CONST_WIDE_INT immediates.
It turns out decimal floating point CONST_DOUBLE get changed into
CONST_WIDE_INT without checking the constraint on the operand, which 
results in failures.  Avoid this by only allowing SF/DF/TF mode floating
point constants in aarch64_legitimate_constant_p.  A similar issue can
occur with 128-bit immediates which may be emitted even when disallowed
in aarch64_legitimate_constant_p, and the constraints in movti_aarch64
don't match.  Fix this with a new constraint and allowing valid immediates
in aarch64_legitimate_constant_p.

Rather than allowing all 128-bit immediates and expanding in up to 8
MOV/MOVK instructions, limit them to 4 instructions and use a literal
load for other cases.  Improve a few TImode tests to use a literal and
ensure they are skipped with -fpic.

This fixes all reported failures.

    gcc/
	PR target/82964
	* config/aarch64/aarch64.md (movti_aarch64): Use Uti constraint.
	* config/aarch64/aarch64.c (aarch64_mov128_immediate): New function.
	(aarch64_legitimate_constant_p): Just support CONST_DOUBLE 
	SF/DF/TF mode to avoid creating illegal CONST_WIDE_INT immediates.
	* config/aarch64/aarch64-protos.h (aarch64_mov128_immediate):
	Add declaration.
	* config/aarch64/constraints.md (aarch64_movti_operand):
	Limit immediates.
	* config/aarch64/predicates.md (Uti): Add new constraint.

    gcc/testsuite/
	PR target/79041
	PR target/82964
	* gcc.target/aarch64/pr79041-2.c: Improve test, disable with fpic.
	* gcc.target/aarch64/pr78733.c: Improve test, disable with fpic.

Co-Authored-By: Richard Sandiford <richard.sandiford@linaro.org>

From-SVN: r256800