What does asm volatile mean?
The __volatile__ modifier on an __asm__ block forces the compiler’s optimizer to execute the code as-is. Without it, the optimizer may think it can be either removed outright, or lifted out of a loop and cached.
What is volatile assembly?
The volatile keyword lets the compiler know that the assembly has an effect other than providing the output value, so that this optimization does not happen.
What is __ asm __ in C?
The __asm keyword invokes the inline assembler and can appear wherever a C or C++ statement is legal. It cannot appear by itself. It must be followed by an assembly instruction, a group of instructions enclosed in braces, or, at the very least, an empty pair of braces.
What is clobber in GCC?
The “cc” clobber indicates that the assembler code modifies the flags register. On some machines, GCC represents the condition codes as a specific hardware register; “cc” serves to name this register.
What is the function of asm?
The asm statement allows you to include assembly instructions directly within C code. This may help you to maximize performance in time-sensitive code or to access assembly instructions that are not readily available to C programs. Note that extended asm statements must be inside a function.
What is volatile memory in C?
C’s volatile keyword is a qualifier that is applied to a variable when it is declared. It tells the compiler that the value of the variable may change at any time–without any action being taken by the code the compiler finds nearby.
What is the use of volatile?
Volatile keyword is used to modify the value of a variable by different threads. It is also used to make classes thread safe. It means that multiple threads can use a method and instance of the classes at the same time without any problem. The volatile keyword can be used either with primitive type or objects.
What is asm instruction?
In computer programming, assembly language (or assembler language), sometimes abbreviated asm, is any low-level programming language in which there is a very strong correspondence between the instructions in the language and the architecture’s machine code instructions.
What is clobber in asm?
A clobbered register is a register which is trashed i.e. modified in unpredictable way by inline assembler. This usually happens when you need a temp. Another example is arithmetic flags register (cc) which is considered to be always clobbered by inline asm by GCC on i386 and x86_64 targets.
What is GCC version?
GNU Compiler Collection
| Screenshot of GCC 10.2 compiling its own source code | |
|---|---|
| Developer(s) | GNU Project |
| Initial release | May 23, 1987 |
| Stable release | 11.2 / July 27, 2021 |
| Preview release | 11.2.0-RC / July 21, 2021 |
https://www.youtube.com/watch?v=rN8kWeyklOs