Can't compare `Float32` with `Rational` on Metal

[efaulhaber]

julia> map(y -> y < 3 // 2, Metal.zeros(1))
ERROR: InvalidIRError: compiling MethodInstance for (::Metal.var"#broadcast_linear#204")(::MtlDeviceVector{…}, ::Base.Broadcast.Broadcasted{…}) resulted in invalid LLVM IR
Reason: unsupported call to an unknown function (call to gpu_malloc)
Stacktrace:
  [1] malloc
    @ ~/.julia/packages/GPUCompiler/AQezv/src/runtime.jl:85
  [2] macro expansion
    @ ~/.julia/packages/GPUCompiler/AQezv/src/runtime.jl:180
  [3] macro expansion
    @ ./none:0
  [4] box
    @ ./none:0
  [5] box_int64
    @ ~/.julia/packages/GPUCompiler/AQezv/src/runtime.jl:209
  [6] ndigits0z
    @ ./intfuncs.jl:701
  [7] <
    @ ./rational.jl:470
  [8] #76
    @ ./REPL[24]:1
  [9] _broadcast_getindex_evalf
    @ ./broadcast.jl:678
 [10] _broadcast_getindex
    @ ./broadcast.jl:651
 [11] getindex
    @ ./broadcast.jl:610
 [12] broadcast_linear
    @ ~/.julia/packages/Metal/N2ABH/src/broadcast.jl:89
Reason: unsupported use of i128 value
Stacktrace:
  [1] toInt128
    @ ./boot.jl:823
  [2] Int128
    @ ./boot.jl:893
  [3] convert
    @ ./number.jl:7
  [4] widen
    @ ./operators.jl:900
  [5] widemul
    @ ./number.jl:277
  [6] <
    @ ./rational.jl:460
  [7] #76
    @ ./REPL[24]:1
  [8] _broadcast_getindex_evalf
    @ ./broadcast.jl:678
  [9] _broadcast_getindex
    @ ./broadcast.jl:651
 [10] getindex
    @ ./broadcast.jl:610
 [11] broadcast_linear
    @ ~/.julia/packages/Metal/N2ABH/src/broadcast.jl:89
[...]

Julia is apparently converting things to Int128 to compare a Float32 with 3 // 2.

julia> Metal.versioninfo()
macOS 15.1.1, Darwin 24.3.0

Toolchain:
- Julia: 1.11.3
- LLVM: 16.0.6

Julia packages: 
- Metal.jl: 1.5.1
- GPUArrays: 11.2.2
- GPUCompiler: 1.1.1
- KernelAbstractions: 0.9.33
- ObjectiveC: 3.4.0
- LLVM: 9.2.0
- LLVMDowngrader_jll: 0.6.0+0

1 device:
- Apple M2 Pro (72.219 MiB allocated)

[christiangnrd]

Thanks for talking the time to submit these issues! Can you open a new issue for the comparison with pi so it’s easier to keep track of?

[efaulhaber]

#551

[alecloudenback]

I'd also note that it's not unique to Float32, comparing rational to an integer also fails with a similar error, e.g.:

julia> map(y -> y < 3 // 2, MtlArray([Int32(1)]))
ERROR: InvalidIRError: compiling MethodInstance for (::Metal.var"#broadcast_linear#226")(::MtlDeviceVector{…}, ::Base.Broadcast.Broadcasted{…}) resulted in invalid LLVM IR
Reason: unsupported use of i128 value