• Merge macros depending on the flags being preserved between calls into a single "asm"-statement as GCC doesn't guarantee their consecutive output even when using consecutive "asm volatile"- statement for them. Remove the otherwise unnecessary "volatile". [1]
• The inline assembler instructions used here alter the condition codes so add them to the clobber list accordingly.
• The inline assembler instructions used here uses output operands before all input operands are consumed so add appropriate modifiers.

Pointed out by: bde [1]
MFC after: 2 weeks