[arm] Avoid STRD with odd register for TARGET_ARM in output_move_double

[arm] Avoid STRD with odd register for TARGET_ARM in output_move_double

In this testcase the user forces an odd register as the starting reg for a DFmode value.
The output_move_double function tries to store that using an STRD instruction.
But for TARGET_ARM the starting register of an STRD must be an even one.
This is always the case with compiler-allocated registers for DFmode values, but the
inline assembly forced our hand here.

This patch  restricts the STRD-emitting logic in output_move_double to not avoid
odd-numbered source registers in STRD.
I'm not a fan of the whole function, we should be exposing a lot of the logic in there
to RTL rather than at the final output stage, but that would need to be fixed separately.

	* config/arm/arm.c (output_move_double): Don't allow STRD instructions
	if starting source register is not even.

	* gcc.target/arm/arm-soft-strd-even.c: New test.

From-SVN: r262250