3 ms·
The xor reg, reg is also special cased because it's a quick way for compilers to reinitialize a register and indicate that future uses of that register don't de
by scheme271 4y ago
The xor reg, reg is also special cased because it's a quick way for compilers to reinitialize a register and indicate that future uses of that register don't depend on any previous operations. It helps the cpu to parallelize any future instructions that use that register since the cpu knows that those instructions don't depend on anything that happens before the the xor.
- Someone 4y agoIt’s not special cased because it's a quick way for compilers to reinitialize a register and indicate that future uses of that register don't depend on any previous operations, it’s special cased to give compilers a quick way to reinitialize a register and indicate that future uses of that register don't depend on any previous operations. https://randomascii.wordpress.com/2012/12/29/the-surprising-subtleties-of-zeroing-a-register/ https://randomascii.wordpress.com/2012/12/29/the-surprising-... is almost ten years old and thus likely dated, but still may be educational.
- nixpulvis 4y agoExactly! I was almost expecting to find a special instruction for this, but then again, why waste the opcodes!?