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472230d192
`[T; N]::zip` is "eager" but most zips are mapped. This causes poor optimization in generated code. This is a fundamental design issue and "zip" is "prime real estate" in terms of function names, so let's free it up again.
39 lines
1.3 KiB
Rust
39 lines
1.3 KiB
Rust
// compile-flags: -C opt-level=3 -C target-cpu=x86-64-v3
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// no-system-llvm
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// only-x86_64
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// ignore-debug (the extra assertions get in the way)
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#![crate_type = "lib"]
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// CHECK-LABEL: @short_integer_map
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#[no_mangle]
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pub fn short_integer_map(x: [u32; 8]) -> [u32; 8] {
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// CHECK: load <8 x i32>
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// CHECK: shl <8 x i32>
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// CHECK: or <8 x i32>
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// CHECK: store <8 x i32>
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x.map(|x| 2 * x + 1)
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}
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// This test is checking that LLVM can SRoA away a bunch of the overhead,
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// like fully moving the iterators to registers. Notably, previous implementations
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// of `map` ended up `alloca`ing the whole `array::IntoIterator`, meaning both a
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// hard-to-eliminate `memcpy` and that the iteration counts needed to be written
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// out to stack every iteration, even for infallible operations on `Copy` types.
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//
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// This is still imperfect, as there's more copies than would be ideal,
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// but hopefully work like #103830 will improve that in future,
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// and update this test to be stricter.
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//
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// CHECK-LABEL: @long_integer_map
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#[no_mangle]
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pub fn long_integer_map(x: [u32; 512]) -> [u32; 512] {
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// CHECK: start:
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// CHECK-NEXT: alloca [512 x i32]
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// CHECK-NEXT: alloca %"core::mem::manually_drop::ManuallyDrop<[u32; 512]>"
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// CHECK-NOT: alloca
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// CHECK: mul <{{[0-9]+}} x i32>
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// CHECK: add <{{[0-9]+}} x i32>
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x.map(|x| 13 * x + 7)
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}
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