• Different performance in HYP and SVC mode ARMv7A?
    I'm doing some testing on Exynos5422 SoC which implements big.LITTLE architecture (A7 + A15), I'm running bare metal application which starts in HYP mode. I haven't returned from HYP mode by accident...
  • UNPREDICTABLE in instruction description (Lord! yet another question)
    In quite many instruction descriptions it says: if d == 15 then UNPREDICTABLE; What does this mean? Can the instruction really work in some unexpected way in each such case or what? I guess if I use...
  • ARM MUL instruction
    Still more instruction things giving me head ache. This time it's the MUL-instruction. What the heck means: Multiply multiplies two register values. The least significant 32 bits of the result are written...
  • Register 'names' in instruction descriptions
    The registers in the instructions are usually 'named' Rn, Rm, Rd, ... Is there some deeper meaning in the names? Usually Rd seems to mean 'destination register' Sometimes Rn is the only operand, sometimes...
  • How to avoid bus error while using neon instruction vld2.32 on cortex a7?
    Hi, I am using imx6ul board which has cortex a7 processor. I am using ffmpeg .s files which has assembly code to integrate into our project to speed up the code.  Here is the ffmpeg code in the file mdct_neon...