Wrong primitive names in LLVM I/O

[jiribenes]

Description

When I try to read from a file:

// repro.effekt

import io
import io/error
import io/files

def main() = eventloop(box {
  with on[IOError].panic;
  with filesystem;

  val contents = do readFile("repro.effekt")
  println(contents)
})

I get the following error:

bash-5.2$ effekt --backend=llvm repro.effekt
opt: ./out/repro.ll:1114:17: error: use of undefined value '@writeFile'
      call void @writeFile(i32 %fd_int, %Pos %buffer, i64 noundef %offset, ptr %onSuccess_ptr, ptr %onFailure_ptr) #0
                ^
Exception in thread "main" java.lang.RuntimeException: Nonzero exit value: 1
  [...]

Investigation 🔍

Upon taking a closer look at ./out/repro.ll, I can see that writeFile is truly neither defined nor declared there.
This happens even when I try to first build, then run.

If I had to guess, then the real name we're looking for is c_file_read in llvm/io.c

effekt/libraries/llvm/io.c

Line 476 in cd741e8

void c_file_read(int32_t fd, struct Pos buffer, int64_t offset, struct Neg* success, struct Neg* failure) {

which got renamed at the end of #469.
When investigating this, I also noticed that the LLVM definition corresponds to the C definition only with the ARM64 calling convention:

effekt/libraries/llvm/io.ll

Line 13 in cd741e8

declare void @c_file_read([2 x i64], [2 x i64], i64, [2 x i64], [2 x i64])

I think it should be something like declare void @c_file_write(i32, %Pos, i64, %Neg*, %Neg*) instead? (or ptr, ptr for the last two, not sure)

[jiribenes]

I'm quite alarmed that the test in stdlib/io/files/async_file_io.effekt didn't catch this 🤔
https://github.com/effekt-lang/effekt/blob/cd741e8a4576c62ab318efd48fc0831958ba7e8d/examples/stdlib/io/files/async_file_io.effekt

EDIT: I tried running the LLVM stdlib tests and it appears that the test in question passes:

effekt.StdlibLLVMTests:
  + examples/stdlib/bytes/bytes.effekt (llvm) 2.928s
  + examples/stdlib/io/promise.effekt (llvm) 1.146s
  + examples/stdlib/io/files/async_file_io.effekt (llvm) 1.416s

The test works when ran directly:

$ effekt --backend=llvm examples/stdlib/io/files/async_file_io.effekt
Running program
Done
Some contents

{ msg: "Hello World!" }

done reading files.

but I don't understand why 😔
Well, the test only uses the readFile function and not the readFile operation which is then handled with filesystem. If I had to guess, the renaming is OK in one of them and not in the other...

[b-studios]

It's writeFile, isn't it? Since we don't write files in the test, dead code elimination removes it before it causes problems