To be able to execute programs written in high level programming languages, they first have to be translated into CPU instructions using a compiler. Language constructs and statements of high level programming languages are CPU architecture independent and do not have any special relationship with individual CPU instructions. The compiler is responsible for selecting and emitting the appropriate instructions which are required for the task at hand.

Assembly languages are a special kind of low level programming languages. Unlike their high level counterparts, assembly languages are not architecture independent but instead target a specific instruction set. While language constructs in high level languages may be compiled into any number of instructions, each statement in an assembly language is translated into one specific CPU instruction. An assembly language can also be thought of as a translation between human readable mnemonics and binary opcodes readable by the CPU (e.g.jmp = 0xE9). A compiler for an assembly language is also called an assembler.

While it is usually a lot more efficient and practical to write code in high level languages, some things still require low level assembly instructions because they are simply not possible to accomplish in other programming languages. This is especially true when using CPU hardware features that can only be accessed using special instructions.

When using the GCC C compiler, it is possible to combine normal code written in C with assembly code in the same source file or even the same function by using GCC inline assembly.

 

On the x86 architecture, the cpuid instruction can be used to retrieve information about the CPU that a program is running on. This includes information about the processor type and manufacturer, as well as information about features and instruction set extensions that are supported by the CPU.
The specific category of information to be retrieved can be selected by setting the eax register (and in some cases also the ecx register) to various ID values before executing the cpuid instruction. The CPU then provides the requested information in the eax, ebx, ecx and edx registers.

Your Task

Use the cpuid instruction to read information about the CPU (5 Points)

Write a program that uses the cpuid instruction to read the following pieces of information about the CPU:

• Manufacturer id string (e.g. ‘GenuineIntel’, ‘AuthenticAMD’, …)
• Processor brand string (e.g. ‘Intel(R) Core(TM) i7-4760HQ CPU @ 2.10GHz’)

You should also determine which level of SIMD instructions are supported the CPU by reading the following feature flags:

• SSE
• SSE2
• SSE3
• SSSE3
• SSE4.1
• SSE4.2
• AVX
• AVX2
• AVX512 Foundation

Print the retrieved information to stdout via the printf calls provided as comments in the code. Do not use any compiler intrinsics or library functions to call the cpuid instruction, only inline assembly. Make sure to properly handle all inputs, outputs and clobbered registers in your inline assembly blocks.

Task 6.2: ABI – Calling Conventions

Calling Conventions

Your Tasks

int64_t charindex(const char* str, char c, uint64_t max_len)
{

    size_t index = 0;
    while(index < max_len && str[index])
    {
        if(str[index] == c)
        {
            return index;
        }

        ++index;
    }

    return -1;
}