What is register %eiz?

Question

In the following assembly code that I dumped out using objdump:

lea    0x0(%esi,%eiz,1),%esi

What is register %eiz? What does the preceding code mean?

Answer 1

See Why Does GCC LEA EIZ?:

Apparently %eiz is a pseudo-register that just evaluates to zero at all times (like r0 on MIPS).