Make generated code for rational constructor and gcd slightly smaller

[KristofferC]

Rational

39 -> 15 SSA values in LLVM and no more GC frames.

Gcd

67 -> 45 SSA values in LLVM and no more GC frames.

[vtjnash]

Why does gcd have a GC frame? These look like they are supposed to lower to the same thing.

[KristofferC]

I thought so too but alas:

julia> @code_llvm gcd(2,3)
; Function gcd
; Location: intfuncs.jl:31
define i64 @julia_gcd_77333998(i64, i64) {
top:
  %2 = alloca %jl_value_t addrspace(10)*, i32 3
  %gcframe = alloca %jl_value_t addrspace(10)*, i32 4

julia> @code_typed gcd(2,3)
CodeInfo(
31 1 ── %1  = %new(Base.:(#throw1#305))::Const(#throw1#305(), false)                   │
32 │    %2  = (a === 0)::Bool                                                          │╻     ==
   └───       goto #3 if not %2                                                        │
   2 ── %4  = (Base.flipsign_int)(b, b)::Int64                                         ││╻     flipsign

A minimal example fails to reproduce though.

[KristofferC]

Actually, the gcframe is not there in 1.0.1 but is there on mater.