instructions

I have very long byte arrays that need to be added to a destination array of type short (or int ). Does such SSE instruction exist? Or maybe their set ? You need to unpack each vector of 8 bit values to two vectors of 16 bit values and then add those. __m128i v = _mm_set_epi8(15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0); __m128i vl = _mm_unpacklo_epi8(v, _mm_set1_epi8(0)); // vl = { 7, 6, 5, 4, 3, 2, 1, 0 } __m128i vh = _mm_unpackhi_epi8(v, _mm_set1_epi8(0)); // vh = { 15, 14, 13, 12, 11, 10, 9, 8 } where v is a vector of 16 x 8 bit values and vl , vh are the two unpacked vectors of 8

This question already has an answer here: Why is a conditional move not vulnerable for Branch Prediction Failure? 5 answers I'm confused where to use cmov instructions and where to use jump instructions in assembly? From performance point of view: What is the difference in both of them? Which one is better? If possible, please explain their difference with an example. Ira Baxter movcc is a so-called predicated instruction. That's fancy-speak for "this instruction executes under a condition (predicate)". Many processors, including the x86, after doing an arithmetic operation (especially compare

Does "ret" instruction cause "esp" register added by 4? Yes, it performs pop eip You can use mov eax, [esp] jmp eax to avoid it. EDIT: It's exactly what ret does. For example, jmp rel_offet is nothing than a hidden add eip, offset , or jmp absolute_offset is mov eip, absolute_offset . Sure there are differences in the way the processor treats them, but from programmer's point of view it's all that happens. Also, there is a special form of ret : ret imm8 that also adds this imm8 value to esp : for example a __stdcall function uses it to discard its parameters from the stack. Not to mention retf

I'd like to statistically profile my C code at the instruction level. I need to know how many additions, multiplications, divisions, etc I'm performing. This is not your usual run of the mill code profiling requirement. I'm an algorithm developer and I want to estimate the cost of converting my code to hardware implementations. For this, I'm being asked the instruction call breakdown during run-time (parsing the compiled assembly isn't sufficient as it doesn't consider loops in the code). After looking around, it seems VMware may offer a possible solution, but I still couldn't find the

I am trying to understand more deeply the instruction selection process in llvm and for that I am debuging step-by-step the CodeGenAndEmitDAG function. I have printed a small function (see below) just before the combine step - the first step in the above function. In the graph I see blue lines and it seems that they are always pointing at "ch" , which I think means "other" machine value type. What I don't understand is the meaning of the blue lines... what is this dependency ? And, am I right about the meaning of "ch" ? is it "other" ? Dashed blue arrows represent non-dataflow dependencies