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add codegen test for equivalent slice implementations #116314

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add codegen test for equivalent slice implementations #116314

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23 changes: 23 additions & 0 deletions tests/codegen/equivalent-slice-impls.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
// This test checks that two equivalent implementations produce the same number of `if` instructions.

#![crate_type = "lib"]

// CHECK-LABEL: @f1
// CHECK: if
pub fn f1(input: &mut &[u64]) -> Option<u64> {
match input {
[] => None,
[first, rest @ ..] => {
*input = rest;
Some(*first)
}
}
}

// CHECK-LABEL: @f2
// CHECK: if
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I would not have expected this to be enough to check that there are equal numbers of if instructions... don't need something that checks there's not a subsequent if too?

pub fn f2(input: &mut &[u64]) -> Option<u64> {
let (first, rest) = input.split_first()?;
*input = rest;
Some(*first)
}