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The new `is_ascii` function is optimized to use the `pmovmskb` vector instruction which tests the high bit in a lane. This corresponds to the same check of whether a byte is ASCII so ASCII validity checking can be vectorized. This instruction does not exist on other platforms so it is likely to regress performance and is gated to all(target_arch = "x86_64", target_feature = "sse2"). Add codegen test Remove crate::mem import for functions included in the prelude
17 lines
507 B
Rust
17 lines
507 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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/// Check that the fast-path of `is_ascii` uses a `pmovmskb` instruction.
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/// Platforms lacking an equivalent instruction use other techniques for
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/// optimizing `is_ascii`.
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// CHECK-LABEL: @is_ascii_autovectorized
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#[no_mangle]
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pub fn is_ascii_autovectorized(s: &[u8]) -> bool {
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// CHECK: load <32 x i8>
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// CHECK-NEXT: icmp slt <32 x i8>
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// CHECK-NEXT: bitcast <32 x i1>
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// CHECK-NEXT: icmp eq i32
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s.is_ascii()
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}
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