cmd/5l: use BLX for indirect branch

[lexprfuncall]

At present, the ARM toolchain will emit the following code for an indirect branch

  ADD lr, pc, #0
  ADD pc, r0, #0

This can be achieved with the following single instruction

  BLX r0

The BLX instruction is available on ARMv4T and all newer processors.

In addition to saving word in the instruction stream, the ARM documentation indicates
that BLX is recognized as procedure calls by the program flow prediction hardware while
moves to the PC are not.

Newer reference

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0438g/BABGEAEF.html

Older reference

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0360f/Cihdbcef.html

[lexprfuncall]

Comment 1:

Sorry, BLX is available on ARMv5 and all newer processors.

[minux]

Comment 2:

sure. see also issue #4718.

Labels changed: added priority-later, removed priority-triage.

[remyoudompheng]

Comment 3:

Labels changed: added arch-arm.

[minux]

Comment 5:

This issue was closed by revision 35e1dea.

Status changed to Fixed.