Literal Directive - Using as















Next: Literal Position Directive,
Previous: Transform Directive,
Up: Xtensa Directives



9.36.5.4 literal


The .literal directive is used to define literal pool data, i.e.,
read-only 32-bit data accessed via L32R instructions.

.literal label, value[, value...]

This directive is similar to the standard .word directive, except
that the actual location of the literal data is determined by the
assembler and linker, not by the position of the .literal
directive. Using this directive gives the assembler freedom to locate
the literal data in the most appropriate place and possibly to combine
identical literals. For example, the code:

entry sp, 40
.literal .L1, sym
l32r a4, .L1

can be used to load a pointer to the symbol sym into register
a4. The value of sym will not be placed between the
ENTRY and L32R instructions; instead, the assembler puts
the data in a literal pool.

Literal pools are placed by default in separate literal sections;
however, when using the --text-section-literals
option (see Command Line Options), the literal
pools for PC-relative mode L32R instructions
are placed in the current section.1
These text section literal
pools are created automatically before ENTRY instructions and
manually after .literal_position directives (see literal_position). If there are no preceding
ENTRY instructions, explicit .literal_position directives
must be used to place the text section literal pools; otherwise,
as will report an error.

When literals are placed in separate sections, the literal section names
are derived from the names of the sections where the literals are
defined. The base literal section names are .literal for
PC-relative mode L32R instructions and .lit4 for absolute
mode L32R instructions (see absolute-literals). These base names are used for literals defined in
the default .text section. For literals defined in other
sections or within the scope of a literal_prefix directive
(see literal_prefix), the following rules
determine the literal section name:


If the current section is a member of a section group, the literal
section name includes the group name as a suffix to the base
.literal or .lit4 name, with a period to separate the base
name and group name. The literal section is also made a member of the
group.

If the current section name (or literal_prefix value) begins with
“.gnu.linkonce.kind.”, the literal section name is formed
by replacing “.kind” with the base .literal or
.lit4 name. For example, for literals defined in a section named
.gnu.linkonce.t.func, the literal section will be
.gnu.linkonce.literal.func or .gnu.linkonce.lit4.func.

If the current section name (or literal_prefix value) ends with
.text, the literal section name is formed by replacing that
suffix with the base .literal or .lit4 name. For example,
for literals defined in a section named .iram0.text, the literal
section will be .iram0.literal or .iram0.lit4.

If none of the preceding conditions apply, the literal section name is
formed by adding the base .literal or .lit4 name as a
suffix to the current section name (or literal_prefix value).




Footnotes[1] Literals for the
.init and .fini sections are always placed in separate
sections, even when --text-section-literals is enabled.