4 ms·
pure decoder width isn't enough to tell you everything. X86 has some commonly used ridiculously compact instructions (e.g. lea) that would turn into 2-3 instruc
by adgjlsfhk1 1y ago
pure decoder width isn't enough to tell you everything. X86 has some commonly used ridiculously compact instructions (e.g. lea) that would turn into 2-3 instructions on most other architectures.
- kimixa 1y agoAlso the op cache - if it hits that the decoder is completely skipped.
- ajross 1y agoThe whole ModRM addressing encoding (to which LEA is basically a front end) is actually really compact, and compilers have gotten frightently good at exploiting it. Just look at the disassembly for some non-trivial code sometime and see what it's doing.
- monocasa 1y agoAdditionally, stuff llike rmw instructions are really like at least three, maybe four or five risc instructions.
- ack_complete 1y agoYes, but so does ARM. ld1 {v0.16b,v1.16b,v2.16b,v3.16b},x0,#64 loads 4 x 128-bit vector registers and post-increments a pointer register.