The following GFX10 opcodes do not support abs/neg modifiers though they should:

v_mov_b32_e64 v_movreld_b32_e64 v_movrels_b32_e64 v_movrelsd_2_b32_e64 v_movrelsd_b32_e64 

These opcodes do not have FP operands but they are actually typeless.
GFX10 SPG states explicitly that these opcodes should support abs/neg modifiers.
Note that v_cndmask_b32_e64 do support abs and neg modifiers.

An example of failed test:

v_mov_b32_e64 v5, -v1 

Expected result:

0x05,0x00,0x81,0xd5,0x01,0x01,0x00,0x20 

Actual output:

error: not a valid operand.