e393f56d37
Refactor the code in the `convert_while_ascii` helper function to make it more suitable for auto-vectorization and also process the full ascii prefix of the string. The generic case conversion logic will only be invoked starting from the first non-ascii character. The runtime on microbenchmarks with ascii-only inputs improves between 1.5x for short and 4x for long inputs on x86_64 and aarch64. The new implementation also encapsulates all unsafe inside the `convert_while_ascii` function. Fixes #123712
24 lines
949 B
Rust
24 lines
949 B
Rust
//@ only-x86_64
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//@ compile-flags: -C opt-level=3
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#![crate_type = "lib"]
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#![no_std]
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#![feature(str_internals)]
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extern crate alloc;
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/// Ensure that the ascii-prefix loop for `str::to_lowercase` and `str::to_uppercase` uses vector
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/// instructions.
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///
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/// The llvm ir should be the same for all targets that support some form of simd. Only targets
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/// without any simd instructions would see scalarized ir.
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/// Unfortunately, there is no `only-simd` directive to only run this test on only such platforms,
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/// and using test revisions would still require the core libraries for all platforms.
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// CHECK-LABEL: @lower_while_ascii
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// CHECK: [[A:%[0-9]]] = load <16 x i8>
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// CHECK-NEXT: [[B:%[0-9]]] = icmp slt <16 x i8> [[A]], zeroinitializer
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// CHECK-NEXT: [[C:%[0-9]]] = bitcast <16 x i1> [[B]] to i16
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#[no_mangle]
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pub fn lower_while_ascii(s: &str) -> (alloc::string::String, &str) {
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alloc::str::convert_while_ascii(s, u8::to_ascii_lowercase)
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}
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