NoteThe Intel® C++ Compiler supports Microsoft-style inline assembly with the -use-msasm compiler option. See your Microsoft documentation for the proper syntax.
The Intel® C++ Compiler supports GNU-like style inline assembly. The syntax is as follows:
asm-keyword [ volatile-keyword ] ( asm-template [ asm-interface ] ) ;
Note
The Intel C++ Compiler supports gcc-style inline ASM if the assembler code uses AT&T* System V/386 syntax.
Caution
The Intel C++ Compiler does not support the mixing UNIX and Microsoft style asms.
| Syntax Element | Description |
|---|---|
| asm-keyword | asm statements begin with the keyword asm. Alternatively, either __asm or __asm__ may be used for compatibility. See Caution statement. |
| volatile-keyword | If the optional keyword volatile is given, the asm is volatile. Two volatile asm statements will never be moved past each other, and a reference to a volatile variable will not be moved relative to a volatile asm. Alternate keywords __volatile and __volatile__ may be used for compatibility. |
| asm-template | The asm-template is a C language ASCII string which specifies how to output the assembly code for an instruction. Most of the template is a fixed string; everything but the substitution-directives, if any, is passed through to the assembler. The syntax for a substitution directive is a % followed by one or two characters. |
| asm-interface | The asm-interface consists of three parts:
1. an optional output-list 2. an optional input-list 3. an optional clobber-list These are separated by colon (:) characters. If the output-list is missing, but an input-list is given, the input list may be preceded by two colons (::)to take the place of the missing output-list. If the asm-interface is omitted altogether, the asm statement is considered volatile regardless of whether a volatile-keyword was specified. |
| output-list | An output-list consists of one or more output-specs separated by commas. For the purposes of substitution in the asm-template, each output-spec is numbered. The first operand in the output-list is numbered 0, the second is 1, and so on. Numbering is continuous through the output-list and into the input-list. The total number of operands is limited to 30 (i.e. 0-29). |
| input-list | Similar to an output-list, an input-list consists of one or more input-specs separated by commas. For the purposes of substitution in the asm-template, each input-spec is numbered, with the numbers continuing from those in the output-list. |
| clobber-list | A clobber-list tells the compiler that the asm uses or changes a specific machine register that is either coded directly into the asm or is changed implicitly by the assembly instruction. The clobber-list is a comma-separated list of clobber-specs. |
| input-spec | The input-specs tell the compiler about expressions whose values may be needed by the inserted assembly instruction. In order to describe fully the input requirements of the asm, you can list input-specs that are not actually referenced in the asm-template. |
| clobber-spec | Each clobber-spec specifies the name of a single machine register that is clobbered. The register name may optionally be preceded by a %. You can specify any valid machine register name. It is also legal to specify "memory" in a clobber-spec. This prevents the compiler from keeping data cached in registers across the asm statement. |