The copy/spill/fill instructions will be used by the register allocator
for splitting live ranges. The copy instruction is also useful when
rewriting values:
If a primary value is rewritten as a secondary result, a copy
instruction can be used instead:
a = foo x
=>
t, vx1 = call ...
a = copy vx1
Since a primary value must be the first value of an instruction, this
doesn't work:
a = foo x
=>
t, a = call ...
All the InstrBuilder methods now consume the builder, and the non-leaf
methods return the dfg mutable reference they were holding.
This makes it possible to construct instruction builders that are only
safe to use once because they are doing more advanced value rewriting.
All of the instruction format an opcode methods are emitted as an
InstBuilder trait instead of adding them to the Bulder struct directly.
The methods only make use of the InstBuilderBase methods to create new
instructions.
This makes it possible to reuse the InstBuilder trait for different ways
of inserting instructions.
RISC-V does not have a flags register, and thus no add-with-carry
instructions. Neither does MIPS.
Add expansions of these instructions in terms of iadd and icmp.
The 'lib/cretonne' directory will be the new root of a stand-alone
cretonne crate containg both Python and Rust sources.
This is in preparation for publishing crates on crates.io.
