Chapter 42. Xtensa Dependent Features

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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

.