regression in 1.13.0-alpha2: `ccall` errors if the function name is a `const` string

[matthias314]

This works in Julia 1.12.2 (provided that you have an x86 processor with BMI extension, of course):

julia> const llvm_pext = "llvm.x86.bmi.pext.64";

julia> pext(x::UInt64, y::UInt64) = ccall(llvm_pext, llvmcall, UInt64, (UInt64, UInt64), x, y);

julia> pext(UInt64(1), UInt64(1))
0x0000000000000001

Julia 1.13.0-alpha2 seems to require a literal string:

julia> pext(UInt64(1), UInt64(1))
ERROR: TypeError: in ccall: first argument not a pointer or valid constant expression, expected Ptr, got a value of type String

julia> pext2(x::UInt64, y::UInt64) = ccall("llvm.x86.bmi.pext.64", llvmcall, UInt64, (UInt64, UInt64), x, y);

julia> pext2(UInt64(1), UInt64(1))
0x0000000000000001

Julia Version 1.13.0-alpha2
Commit 7f76b76527d (2025-11-30 19:52 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × Intel(R) Core(TM) i3-10110U CPU @ 2.10GHz
  WORD_SIZE: 64
  LLVM: libLLVM-20.1.8 (ORCJIT, skylake)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 4 virtual cores)

[adienes]

I imagine this was changed by #59165, and since it's tagged minor change it also seems the difference in behavior is intentional. I did not really follow neither the motivation for the PR nor its implementation though so I can't say much more of use.