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00bd24766f
I happened to notice today that there's actually two such calls emitted in the assembly: <https://rust.godbolt.org/z/1Wbbd3Ts6> Since they're impossible, hopefully telling LLVM that will also help optimizations elsewhere.
27 lines
661 B
Rust
27 lines
661 B
Rust
//@ compile-flags: -O
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#![crate_type = "lib"]
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use std::iter::StepBy;
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use std::slice::Iter;
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// The constructor for `StepBy` ensures we can never end up needing to do zero
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// checks on denominators, so check that the code isn't emitting panic paths.
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// CHECK-LABEL: @step_by_len_std
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#[no_mangle]
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pub fn step_by_len_std(x: &StepBy<Iter<i32>>) -> usize {
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// CHECK-NOT: div_by_zero
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// CHECK: udiv
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// CHECK-NOT: div_by_zero
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x.len()
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}
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// CHECK-LABEL: @step_by_len_naive
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#[no_mangle]
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pub fn step_by_len_naive(x: Iter<i32>, step_minus_one: usize) -> usize {
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// CHECK: udiv
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// CHECK: call{{.+}}div_by_zero
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x.len() / (step_minus_one + 1)
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}
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