Enable assembler functions directive
Format
.ENABLE argument-list
.ENABL argument-list
1 – Parameter
argument-list
One or more of the symbolic arguments You can use either the long
form or the short form of the symbolic arguments.
If you specify multiple arguments, separate them with commas,
spaces, or tabs.
Table 6 .ENABLE and .DISABLE Symbolic Arguments
Short Default
Long Form Form Condition Function
ALIGN_CODE Disabled The code alignment option aligns
certain branch target labels. The
ALIGN_CODE option is disabled for
the assembly unit if any one of the
following is true:
o /NOALIGNMENT=CODE is specified on
the command line.
o .DISABLE ALIGN_CODE is specified in
the source program.
o The /ALIGNMENT=CODE option is
defaulted.
ALIGN_DATA Disabled When ALIGN_DATA is disabled, the data-
storage directives put each succeeding
item on the next byte boundary.
When ALIGN_DATA is enabled, the data-
storage directives put each succeeding
item on natural boundaries (such as
words on word boundaries, longwords on
longword boundaries) and add pad bytes
as necessary.
Accessing data on anything other than
natural boundaries usually incurs a
significant performance penalty.
You can enable or disable the
ALIGN_DATA option for specific ranges
within your program.
FLOAT Enabled Controls whether the assembler
generates floating-point instructions
when optimizing code and performing
code-label alignment.
Currently, the only floating-point
instruction generated by the assembler
during optimization and alignment
processing is FNOP, the floating-
point no-operation instruction. If you
specify .DISABLE FLOAT, the assembler
does not generate any floating-point
instructions as part of optimization
and alignment processing.
The initial value of this option is
specified by the /ENVIRONMENT=[NO]FLOAT
command-line option. The last value of
the FLOAT option at the end of assembly
determines whether FLOAT is enabled or
DISABLED.
GLOBAL GBL Enabled When GLOBAL is enabled, the assembler
implicitly treats any undefined symbol
as an external reference defined in
another module. If the GLOBAL option
is disabled, the assembler issues
a warning and implicitly treats
the undefined symbol as an external
reference assumed to be defined in
another module. The last value of the
GLOBAL option at the end of assembly
determines whether the GLOBAL option is
enabled or disabled.
LOCAL_BLOCK LSB Disabled Used to override the default assembler
behavior to define a temporary label
block. (A temporary label is of the
form n$ where n represents a number.)
A temporary label block is usually
delimited by two user-defined local
or global labels. However, the .ENABLE
LOCAL_BLOCK directive defines the start
of a block that is terminated by one of
the following:
o A second .ENABLE LOCAL_BLOCK
directive.
o A .DISABLE LOCAL_BLOCK directive
followed by a user-defined local or
global label, or a .PSECT directive.
PEEPHOLE Disabled Peephole optimization reduces the
strength of certain instructions and
eliminates instructions where possible.
The PEEPHOLE option is disabled for
the assembly unit if any one of the
following is true:
o /NOOPTIMIZE=PEEPHOLE is specified on
the command line.
o .DISABLE PEEPHOLE is specified in
the source program.
o The PEEPHOLE option is defaulted.
PREPROCESSOR_ Enabled When PREPROCESSOR_OUTPUT is enabled,
OUTPUT the MACRO-64 preprocessor processes
your source statements and outputs to
the preprocessor-output file. If the
PREPROCESSOR_OUTPUT option is disabled,
your source statements are processed
as before. However, output of these
statements to the preprocessor-output
file is suppressed.
Neither .ENABLE PREPROCESSOR_OUTPUT
nor .DISABLE PREPROCESSOR_OUTPUT is
passed through to the preprocessor-
output file. These two directives
have no effect unless you specify
/PREPROCESSOR_ONLY on the command line.
SCHEDULE Disabled Instruction scheduling optimization
reorders instructions to more optimally
utilize the instruction pipeline.
The SCHEDULE option is disabled for
the assembly unit if any one of the
following is true:
o /NOOPTIMIZE=SCHEDULE is specified on
the command line.
o .DISABLE SCHEDULE is specified in
the source program.
o The SCHEDULE option is defaulted.
2 – Description
.ENABLE enables the specified assembly function. .ENABLE and
its negative form, .DISABLE, control the following assembler
functions:
o Creating local label blocks
o Specifying that undefined symbol references are external
references
o Enabling or disabling specific optimizations for the assembly
unit
You can enable one or more specific optimization options with
either the .ENABLE directive or the /OPTIMIZE command-line
qualifier, or both. If you explicitly disable one or more
specific optimization options with the .DISABLE directive, those
optimization options are disabled regardless of the command-line
options you specify.
3 – Notes
o The alternate form of .ENABLE is .ENABL.
4 – Examples
Example 1
The following example shows the ALIGN_DATA option:
.PSECT A, NOEXE
.ENABLE ALIGN_DATA ; Align on natural
; natural boundaries
A: .BYTE 1 ;
B: .QUAD 1000 ; B is allocated at
; a natural boundary -
; specifically at A + 7
.DISABLE ALIGN_DATA ;
C: .BYTE 2 ;
D: .QUAD 1001 ; D is allocated at
; an unaligned boundary -
; specifically C + 1
Example 2
The following example shows the GLOBAL option disabled:
.DISABLE GLOBAL
.ADDRESS X ; Assembler issues a warning
.END
Example 3
The following example shows the LOCAL_BLOCK option enabled:
.ENABLE LOCAL_BLOCK
.PSECT A,NOEXE
A1::
5$: .PROCEDURE_DESCRIPTOR PROC_1 ; Temporary label 5$
.blkb 32
A2::
.address 5$ ; By default the declaration
; of A2 would have ended the
; temporary label block and
; made this reference to 5$
; illegal. However, this default
; behavior has been overridden
; by the use of .ENABLE LOCAL_BLOCK.
.DISABLE LOCAL_BLOCK
.END
Example 4
The following example shows an unoptimized and optimized list
of instructions with the SCHEDULE and PEEPHOLE options enabled:
.ENABLE PEEPHOLE,SCHEDULE
.psect A,EXE,QUAD ; unoptimized
TRAPB
A::ADDF F1,F2,F3
ADDF F4,F5,F6
ADDL R1,R2,R3
ADDL R4,R5,R6
This example shows the optimized list of instructions:
.ENABLE PEEPHOLE,SCHEDULE
.psect A,EXE,QUAD ; optimized
A::ADDF F1,F2,F3
ADDL R1,R2,R3
ADDF F4,F5,F6
ADDL R4,R5,R6
The following example shows a repeat block that initializes
a block of 1000 longwords to the values of 0 through 999. The
.DISABLE PREPROCESSOR_OUTPUT directive suppresses from the
preprocessor output file those statements that are incompatible
with the OSF/1 Assembler.
.DISABLE PREPROCESSOR_OUTPUT
I=0
.REPEAT 1000
.ENABLE PREPROCESSOR_OUTPUT
.LONG %INTEGER(I)
.DISABLE PREPROCESSOR_OUTPUT
I = I + 1
.ENDR