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377a0c88a9
Consolidate all the panicking functions in `slice/index.rs` to use a single `slice_index_fail` function, similar to how it is done in `str/traits.rs`.
37 lines
1.2 KiB
Rust
37 lines
1.2 KiB
Rust
//@ compile-flags: -Copt-level=3
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//@ min-llvm-version: 20
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#![crate_type = "lib"]
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// This test verifies that LLVM 20 properly optimizes the bounds check
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// when accessing the last few elements of a slice with proper conditions.
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// Previously, this would generate an unreachable branch to
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// slice_index_fail even when the bounds check was provably safe.
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// CHECK-LABEL: @last_four_initial(
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#[no_mangle]
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pub fn last_four_initial(s: &[u8]) -> &[u8] {
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// Previously this would generate a branch to slice_index_fail
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// that is unreachable. The LLVM 20 fix should eliminate this branch.
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// CHECK-NOT: slice_index_fail
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// CHECK-NOT: unreachable
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let start = if s.len() <= 4 { 0 } else { s.len() - 4 };
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&s[start..]
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}
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// CHECK-LABEL: @last_four_optimized(
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#[no_mangle]
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pub fn last_four_optimized(s: &[u8]) -> &[u8] {
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// This version was already correctly optimized before the fix in LLVM 20.
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// CHECK-NOT: slice_index_fail
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// CHECK-NOT: unreachable
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if s.len() <= 4 { &s[0..] } else { &s[s.len() - 4..] }
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}
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// Just to verify we're correctly checking for the right thing
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// CHECK-LABEL: @test_bounds_check_happens(
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#[no_mangle]
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pub fn test_bounds_check_happens(s: &[u8], i: usize) -> &[u8] {
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// CHECK: slice_index_fail
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&s[i..]
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}
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