Miscellaneous Intrinsics

Intel® C++ Compiler Classic Developer Guide and Reference

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Date 3/31/2023

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Miscellaneous Intrinsics

The following tables list and describe intrinsics that you can use across all Intel® architectures, except where noted. These intrinsics are available for both Intel® and non-Intel microprocessors but they may perform additional optimizations for Intel® microprocessors than they perform for non-Intel microprocessors.

NOTE:

Casting functions for various INT and FP types for use in intrinsic functions across Intel® architectures only change the type; they do not convert between integer and floating point values.

Intrinsic	Description
Intrinsics for all Supported Intel® Architectures
`__cpuid`	Queries the processor for information about processor type and supported features. The Intel® C++ Compiler Classic supports the Microsoft* implementation of this intrinsic. See the Microsoft documentation for details.
`void *_alloca(int)`	Allocates memory in the local stack frame. The memory is automatically freed upon return from the function.
`int _bit_scan_forward(int x)`	Returns the bit index of the least significant set bit of `x`. If `x` is 0, the result is undefined.
`int _bit_scan_reverse(int)`	Returns the bit index of the most significant set bit of `x`. If `x`is 0, the result is undefined.
`unsigned char _BitScanForward(unsigned __int32 p, unsigned __int32 b);` and for Intel® 64 architecture only: `unsigned char _BitScanForward64(unsigned __int32 p, unsigned __int64 b);`	Sets `*p` to the bit index of the least significant set bit of `b` or leaves it unchanged if `b` is zero. The function returns a non-zero result when `b` is non-zero and returns zero when `b` is zero.
`unsigned char _BitScanReverse(unsigned __int32 p, unsigned __int32 b);` and for Intel® 64 architecture only: `unsigned char _BitScanReverse64(unsigned __int32 p, unsigned __int64 b);`	Sets `*p` to the bit index of the most significant set bit of `b` or leaves it unchanged if `b` is zero. The function returns a non-zero result when `b` is non-zero and returns zero when `b` is zero.
`unsigned char _bittest(__int32 p, __int32 b);` and for Intel® 64 architecture only: `unsigned char _bittest64(__int64 p, __int64 b);`	Returns the bit in position `b` of the memory addressed by `p`.
`unsigned char _bittestandcomplement(__int32 p, __int32 b);` and for Intel® 64 architecture only: `unsigned char _bittestandcomplement64(__int64 p, __int64 b);`	Returns the bit in position `b` of the memory addressed by `p`, then compliments that bit.
`unsigned char _bittestandreset(__int32 p, __int32 b);` and for Intel® 64 architecture only: `unsigned char _bittestandreset64(__int64 p, __int64 b);`	Returns the bit in position `b` of the memory addressed by `p`, then resets that bit to 0.
`unsigned char _bittestandset(__int32 p, __int32 b);` and for Intel® 64 architecture only: `unsigned char _bittestandset64(__int64 p, __int64 b);`	Returns the bit in position `b` of the memory addressed by `p`, then sets the bit to 1.
`int _bswap(int)`	Reverses the byte order of `x`. Swaps 4 bytes; bits 0-7 are swapped with bits 24-31, bits 8-15 are swapped with bits 16-23.
`__int64 _bswap64(__int64 x)`	Reverses the byte order of `x`. Swaps 8 bytes; bits 0-7 are swapped with bits 56-63, bits 8-15 are swapped with bits 48-55, bits 16-23 are swapped with bits 40-47, and bits 24-31 are swapped with bits 32-39.
`unsigned int __cacheSize(unsigned int cacheLevel)`	__cacheSize(n) returns the size in kilobytes of the cache at level n. 1 represents the first-level cache. 0 is returned for a non-existent cache level. For example, an application may query the cache size and use it to select block sizes in algorithms that operate on matrices.
`void _enable(void)`	Enables the interrupt.
`unsigned __int32 _castf32_u32(float)`	Casts `float` value to unsigned 32-bit integer.
`unsigned __int64 _castf64_u64(double)`	Casts `double` value to unsigned 64-bit integer.
`float _castu32_f32(unsigned __int32)`	Casts unsigned 32-bit integer to `float32`.
`double _castu64_f64(unsigned __int64)`	Casts unsigned 32-bit integer to `float64`.
`void _disable(void)`	Disables the interrupt.
`int _in_byte(int)`	Intrinsic that maps to the IA-32 instruction IN. Transfer data byte from port specified by argument.
`int _in_dword(int)`	Intrinsic that maps to the IA-32 instruction IN. Transfer double word from port specified by argument.
`int _in_word(int)`	Intrinsic that maps to the IA-32 instruction IN. Transfer word from port specified by argument.
`int _inp(int)`	Same as _in_byte.
`int _inpd(int)`	Same as _in_dword.
`int _inpw(int)`	Same as _in_word.
`int _out_byte(int, int)`	Intrinsic that maps to the IA-32 instruction OUT. Transfer data byte in second argument to port specified by first argument.
`int _out_dword(int, int)`	Intrinsic that maps to the IA-32 instruction OUT. Transfer double word in second argument to port specified by first argument.
`int _out_word(int, int)`	Intrinsic that maps to the IA-32 instruction OUT. Transfer word in second argument to port specified by first argument.
`int _outp(int, int)`	Same as _out_byte.
`int _outpw(int, int)`	Same as _out_word.
`int _outpd(int, int)`	Same as _out_dword.
`int _popcnt32(int x)`	Returns the number of set bits in `x`.
`int _popcnt64(__int64 x)`	Returns the number of set bits in `x`.
`__int64 _rdpmc(int p)`	Returns the current value of the 40-bit performance monitoring counter specified by `p`.
Intrinsics for IA-32 and Intel® 64 Architectures
`__int64 _rdtsc(void)`	Returns the current value of the processor's 64-bit time stamp counter.
`int _setjmp(jmp_buf)`	A fast version of setjmp(), which bypasses the termination handling. Saves the callee-save registers, stack pointer and return address.
`int __pin_value(char *annotation)`	Bypasses code that executes only in PIN mode. Especially useful with Intel® oneAPI Threading Building Blocks (oneTBB), which adds specified annotations to the object file so that code is executed in PIN mode.

Parent topic: Intrinsics for All Intel® Architectures

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