5.7.7.30 Loop-rename-registers Option
The -mloop-rename-registers
option reallocates values that are referenced inside
a loop and that are stored in high-numbered registers (r8-r15)
to low-numbered registers (r0 - r7) that are not otherwise used
in the loop. High-numbered registers are not accessible to all
16-bit instructions and avoiding these registers allows more
efficient instructions, such as
cbz
/cbnz
, to be
used more often. This option is automatically enabled when using
-O2
or -O3
.
The -mloop-rename-registers
form of this option does not reallocate register
contents within loops.