Developer Guide and Reference

Contents

fnsplit, Qfnsplit

Enables function splitting.

Syntax

Linux:
-fnsplit
[
=
n
]
-no-fnsplit
macOS:
None
Windows:
/Qfnsplit
[
:
n
]
/Qfnsplit-
Arguments
n
Is an optional positive integer indicating the threshold number.
The blocks can be placed into a different code segment if they are only reachable via a conditional branch whose taken probability is less than the specified
n
. Branch taken probability is heuristically calculated by the compiler and can be observed in assembly listings.
The range for
n
is 0 <= n <= 100.
Default
OFF
Function splitting is not enabled. However, function grouping is still enabled.
Description
This option enables function splitting. If you specify
[Q]fnsplit
with no
n
, you must also specify option
[Q]prof-use
, or the option will have no effect and no function splitting will occur.
If you specify
n
, function splitting is enabled and you do not need to specify option
[Q]prof-use
.
To disable function splitting when you use option
[Q]prof-use
, specify
/Qfnsplit-
(Windows*) or
-no-fnsplit
(Linux*).
Function splitting is generally not supported when exception handling is turned on for C/C++ routines in the stack of called routines. See also
-fexceptions
(Linux*)
and the C/C++ option
/EH
(Windows*)
.
Alternate Options
Linux:
-freorder-blocks-and-partition
(a gcc option)
Windows: None

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804