tcg-arm: Implement deposit for armv7

We have BFI and BFC available for implementing it.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-arm: Use bic to implement and with constant

This greatly improves the code we can produce for deposit
without armv7 support.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-arm: Handle negated constant arguments to and/sub

This greatly improves code generation for addition of small
negative constants.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-arm: Improve constant generation

Try fully rotated arguments to mov and mvn before trying movt
or full decomposition.  Begin decomposition with mvn when it
looks like it'll help.  Examples include

-:        mov   r9, #0x00000fa0
-:        orr   r9, r9, #0x000ee000
-:        orr   r9, r9, #0x0ff00000
-:        orr   r9, r9, #0xf0000000
+:        mvn   r9, #0x0000005f
+:        eor   r9, r9, #0x00011000

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-arm: Fold epilogue into INDEX_op_exit_tb

The epilogue on ARM is one pop instruction, that pops the return
address into PC.  Avoid the jump to jump for this case.  Use the
standard movi32 routine for loading the return value if it's easy.

Signed-off-by: Richard Henderson <rth@twiddle.net>