Chapter 42. Xtensa Dependent Features
247
42.5.8. freeregs
This directive tells the assembler that the given registers are unused in the region.
.begin freeregs ri[,ri...]
.end freeregs
This allows the assembler to use these registers for relaxations or optimizations. (They are actually
only for relaxations at present, but the possibility of optimizations exists in the future.)
Nested
freeregs
directives can be used to add additional registers to the list of those available to the
assembler. For example:
.begin freeregs a3, a4
.begin freeregs a5
has the effect of declaring
a3
,
a4
, and
a5
all free.
42.5.9. frame
This directive tells the assembler to emit information to allow the debugger to locate a function's stack
frame. The syntax is:
.frame reg, size
where
reg
is the register used to hold the frame pointer (usually the same as the stack pointer) and
size
is the size in bytes of the stack frame. The
.frame
directive is typically placed immediately
after the
ENTRY
instruction for a function.
In almost all circumstances, this information just duplicates the information given in the function's
ENTRY
instruction; however, there are two cases where this is not true:
1. The size of the stack frame is too big to fit in the immediate field of the
ENTRY
instruction.
2. The frame pointer is different than the stack pointer, as with functions that call
alloca
.






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