pub fn load_of(ty: Type) -> Option<&'static str>Expand description
What the instruction that reads an argument of that type out of memory is called.
Keyed off the same two questions head_of asks and answering for the same set of types, so
that a parameter this compiler can bring in from a register is one it can bring in from the
caller’s stack as well. A width one of them covered and the other did not would be a function
turned away for where its sixth argument happened to land.
Reading a narrow argument at its own width and not at a word is deliberate. The caller wrote a
whole word, but what it put in the part above the value is not something the convention says, so
the bits this reads are exactly the bits that mean anything. That is the same thing an argument
arriving in a register gets: x64.arg_val_8 says the low byte of that register is the argument
and says nothing at all about the rest of it.