Intrinsic function

Source: Wikipedia, the free encyclopedia.
This article is about compiler intrinsic functions. For X toolkit, see X Toolkit Intrinsics.

In

subroutine) available for use in a given programming language whose implementation is handled specially by the compiler. Typically, it may substitute a sequence of automatically generated instructions for the original function call, similar to an inline function.[1]
Unlike an inline function, the compiler has an intimate knowledge of an intrinsic function and can thus better integrate and optimize it for a given situation.

Compilers that implement intrinsic functions may enable them only when a program requests optimization, otherwise falling back to a default implementation provided by the language runtime system (environment).

Vectorization and parallelization

Intrinsic functions are often used to explicitly implement

platform
. Some intrinsics are used to provide additional constraints to the optimizer, such as values a variable cannot assume.[2]

By programming language

C and C++

Compilers for C and C++, of Microsoft,[3] Intel,[1] and the GNU Compiler Collection (GCC)[4] implement intrinsics that map directly to the

Microsoft Visual Studio does not support inline assembly for x86-64.[5][6][7][8]
To compensate for this, new intrinsics have been added that map to standard assembly instructions that are not normally accessible through C/C++, e.g., bit scan.

Some C and C++ compilers provide non-portable platform-specific intrinsics. Other intrinsics (such as

low level programming language implementations, while still benefiting from the C++ type system and inlining; hence the advantage over linking to hand-written assembly object files, using the C application binary interface
(ABI).

Examples

 uint64_t __rdtsc        ();                                                          // return internal CPU clock counter
 uint64_t __popcnt64     (uint64_t n);                                                // count of bits set in n
 uint64_t _umul128       (uint64_t Factor1, uint64_t Factor2, uint64_t* HighProduct); // 64 bit * 64 bit => 128 bit multiplication
 __m512   _mm512_add_ps  (__m512 a, __m512 b);                                        // calculates a + b for two vectors of 16 floats
 __m512   _mm512_fmadd_ps(__m512 a, __m512 b, __m512 c);                              // calculates a*b + c for three vectors of 16 floats

[11]

Java

The HotSpot Java virtual machine's (JVM) just-in-time compiler also has intrinsics for specific Java APIs.[12] Hotspot intrinsics are standard Java APIs which may have one or more optimized implementation on some platforms.

PL/I

ANSI/ISO PL/I defines nearly 90 builtin functions.[13] These are conventionally grouped as follows:[14]: 337–338 

  • String-handling builtin functions such as INDEX, LENGTH
  • Arithmetic builtin functions such as ABS, CEIL, ROUND
  • Mathematical builtin functions like SIN, COS, LOG, ERF
  • Array-handling builtin functions, for example ANY, ALL, PROD
  • Condition-handling builtin functions like ONCODE, ONFILE
  • Storage Control builtin functions, for example ADDR, POINTER
  • Input-Output builtins: LINENO
  • Miscellaneous builtin functions like DATE and TIME

Individual compilers have added additional builtins specific to a machine architecture or operating system.

A builtin function is identified by leaving its name undeclared and allowing it to default, or by declaring it BUILTIN. A user-supplied function of the same name can be substituted by declaring it as ENTRY.

References

  1. ^ a b "Intel® C++ Compiler 19.1 Developer Guide and Reference". Intel® C++ Compiler Documentation. 16 December 2019. Retrieved 2020-01-17.
  2. ^ The Clang Team (2020). "Clang Language Extensions". Clang 11 documentation. Retrieved 2020-01-17. Builtin Functions
  3. ^ MSDN. "Compiler Intrinsics". Microsoft. Retrieved 2012-06-20.
  4. ^ GCC documentation. "Built-in Functions Specific to Particular Target Machines". Free Software Foundation. Retrieved 2012-06-20.
  5. ^ MSDN. "Intrinsics and Inline Assembly". Microsoft. Archived from the original on 2018-01-02. Retrieved 2010-04-16.
  6. ^ MSDN. "Intrinsics and Inline Assembly". Microsoft. Retrieved 2011-09-28.
  7. ^ MSDN. "Intrinsics and Inline Assembly". Microsoft. Retrieved 2011-09-28.
  8. ^ MSDN. "Intrinsics and Inline Assembly". Microsoft. Retrieved 2011-09-28.
  9. ^ "Vector Extensions". Using the GNU Compiler Collection (GCC). Retrieved 2020-01-16.
  10. ^ "Sony open sources Vector Math and SIMD math libraries (Cell PPU/SPU/other platforms)". Beyond3D Forum. Retrieved 2020-01-17.
  11. ^ Intel Intrinsics
  12. ^ Mok, Kris (25 February 2013). "Intrinsic Methods in HotSpot VM". Slideshare. Retrieved 2014-12-20.
  13. ^ ANSI X3 Committee (1976). American National Standard programming language PL/I.{{cite book}}: CS1 maint: numeric names: authors list (link)
  14. ^ IBM Corporation (1995). IBM PL/I for MVS & VM Language Reference.

External links

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