Macro Functions to Read and Write Control Registers

Intel® C++ Compiler Classic Developer Guide and Reference

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ID 767249

Date 3/31/2023

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Visible to Intel only — GUID: GUID-DD59AB3B-27FC-4AAE-8459-D669F5641573

The following macro functions enable you to read and write bits to and from the control register.

Exception State Macros	Macro Arguments
_MM_SET_EXCEPTION_STATE(x)	_MM_EXCEPT_INVALID
_MM_GET_EXCEPTION_STATE()	_MM_EXCEPT_DIV_ZERO
	_MM_EXCEPT_DENORM
Macro Definitions Write to and read from the six least significant control register bits, respectively.	_MM_EXCEPT_OVERFLOW
	_MM_EXCEPT_UNDERFLOW
	_MM_EXCEPT_INEXACT

The following example tests for a divide-by-zero exception.

Exception Mask Macros	Macro Arguments
_MM_SET_EXCEPTION_MASK(x)	_MM_MASK_INVALID
_MM_GET_EXCEPTION_MASK ()	_MM_MASK_DIV_ZERO
	_MM_MASK_DENORM
Macro Definitions Write to and read from bit 7 – 12 control register bits, respectively. NOTE: All six exception mask bits are always affected. Bits not set explicitly are cleared.	_MM_MASK_OVERFLOW
	_MM_MASK_UNDERFLOW
	_MM_MASK_INEXACT

To mask the overflow and underflow exceptions and unmask all other exceptions, use the macros as follows:

_MM_SET_EXCEPTION_MASK(MM_MASK_OVERFLOW | _MM_MASK_UNDERFLOW)

The following table lists the macros to set and get rounding modes, and the macro arguments that can be passed with the macros.

Rounding Mode	Macro Arguments
_MM_SET_ROUNDING_MODE(x)	_MM_ROUND_NEAREST
_MM_GET_ROUNDING_MODE()	_MM_ROUND_DOWN
Macro Definition Write to and read from bits 13 and 14 of the control register.	_MM_ROUND_UP
	_MM_ROUND_TOWARD_ZERO

To test the rounding mode for round toward zero, use the _MM_ROUND_TOWARD_ZERO macro as follows.

if (_MM_GET_ROUNDING_MODE() == _MM_ROUND_TOWARD_ZERO) { 
/* Rounding mode is round toward zero */ 
}

The following table lists the macros to set and get the flush-to-zero mode and the macro arguments that can be used.

Flush-to-Zero Mode	Macro Arguments
_MM_SET_FLUSH_ZERO_MODE(x)	_MM_FLUSH_ZERO_ON
_MM_GET_FLUSH_ZERO_MODE()	_MM_FLUSH_ZERO_OFF
Macro Definition Write to and read from bit 15 of the control register.

Flush-to-Zero Mode

Macro Arguments

_MM_SET_FLUSH_ZERO_MODE(x)

_MM_FLUSH_ZERO_ON

_MM_GET_FLUSH_ZERO_MODE()

_MM_FLUSH_ZERO_OFF

Macro Definition

Write to and read from bit 15 of the control register.

To disable the flush-to-zero mode, use the _MM_FLUSH_ZERO_OFF macro.

_MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_OFF)

Parent topic: Macro Functions