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Add test for ilog2 #93

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13 changes: 13 additions & 0 deletions tests/assembly/ilog2.rs
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// assembly-output: bpf-linker
// compile-flags: --crate-type cdylib -C link-arg=--unroll-loops -C link-arg=-O3
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do we need unroll-loops and 03? seems superfluous, see https://en.wikipedia.org/wiki/Chekhov%27s_gun

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Almost certainly copy-pasted this 😀

#![no_std]
// bpf target did not historically support the ilog2 operation because LLVM did
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what are you testing here? There's no CHECK; can you add some?

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TBH I do not remember the details of how to use this testing. To my memory, I wanted this to build successfully, but it currently doesn't because ilog2 IL is refused by LLVM.

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OK. Should we close this?

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No, because this is actually affecting some of my code. Right now, I have to manually compute ilog2. If I ever depended on a crate which uses this functionality, I would be screwed 😅

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How do I correctly write this testcase to check that the compilation is successful?

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What is it you're looking for, here?

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How do I correctly write this testcase to check that the compilation is successful?

Read the llvm-filecheck docs? Have you tried running this locally?

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What is it you're looking for, here?

Historically, ilog2 would cause a linkage error that was very difficult to diagnose.

Have you tried running this locally?

Not recently, no. I'll try to take a look at it this week and update it according to the llvm-filecheck docs.

// not have a way to do leading/trailing bits

// aux-build: loop-panic-handler.rs
extern crate loop_panic_handler;

#[no_mangle]
fn foo(arg: &mut u64) {
*arg = arg.ilog2() as u64;
}