Developer Guide and Reference

Contents

ftz, Qftz

Flushes
denormal
results to zero.

Syntax

Linux and macOS:
-ftz
-no-ftz
Windows:
/Qftz
/Qftz-
Arguments
None
Default
-ftz
or
/Qftz
Denormal
results are flushed to zero.
Every optimization option
O
level, except
O0
, sets
[Q]ftz
.
Description
This option flushes
denormal
results to zero when the application is in the gradual underflow mode. It may improve performance if the
denormal
values are not critical to your application's behavior.
The
[Q]ftz
option has no effect during compile-time optimization.
The
[Q]ftz
option sets or resets the FTZ and the DAZ hardware flags. If FTZ is ON,
denormal
results from floating-point calculations will be set to the value zero. If FTZ is OFF,
denormal
results remain as is. If DAZ is ON,
denormal
values used as input to floating-point instructions will be treated as zero. If DAZ is OFF,
denormal
instruction inputs remain as is. Systems using Intel® 64 architecture have both FTZ and DAZ. FTZ and DAZ are not supported on all IA-32 architectures.
When the
[Q]ftz
option is used in combination with an SSE-enabling option on systems using IA-32 architecture (for example, the
[Q]xSSE2
option), the compiler will insert code in the main routine to set FTZ and DAZ. When
[Q]ftz
is used without such an option, the compiler will insert code to conditionally set FTZ/DAZ based on a run-time processor check.
If you specify option