Hi,

The LDR rX, =cst pseudo-instruction suffers from two issues for loading
integer constants in Thumb mode:

- movs is used if the constant and register can be encoded using that
   instruction which leads to unexpected behavior due to its flag-setting
   behavior
- mov.w, movw and mvn are used for r13 (sp) and r15 (pc) but these
   encoding are marked as UNPREDICTABLE

This patch fixes those issues and update testing accordingly.

ChangeLog entry is as follows:

*** gas/ChangeLog ***

2017-04-20  Thomas Preud'homme  <thomas.preudhomme@arm.com>

	* config/tc-arm.c (move_or_literal_pool): Remove code generating MOVS.
	Forbid MOV.W and MOVW if destination is SP or PC.
	* testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.s: Explain
	expectation of LDR not generating a MOVS for low registers and small
	constants.  Add tests of MOVW generation.
	* testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.d: Update
	expected disassembly.


Testsuite shows no regression with this patch.

Is this ok for master?

Best regards,

Thomas