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Mar 12, 2019
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test that various pointer types hit UTF8 decoding fast path #21743

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112 changes: 112 additions & 0 deletions test/SILOptimizer/utf8_decoding_fastpath.swift
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// RUN: %target-swift-frontend -Xllvm -swiftmergefunc-threshold=0 -parse-as-library -O -target-cpu core2 -emit-ir %s | %FileCheck %s
// REQUIRES: optimized_stdlib,CPU=x86_64

// This is an end-to-end test to ensure that the optimizer generates
// good code for various ways to create a String from a Sequence of UTF-8
// bytes for which a fast path exists.

// Please note: this test targets "core2" to ensure consistent output
// on all x86 host processors.

@inline(never)
func blackhole<T>(_ value: T) {}

// UnsafeBufferPointer<UInt8>
// ==========================
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}s22utf8_decoding_fastpath15decodeUBPAsUTF8ySSSRys5UInt8VGF{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK-LAST: ret
public func decodeUBPAsUTF8(_ ptr: UnsafeBufferPointer<UInt8>) -> String {
return String(decoding: ptr, as: Unicode.UTF8.self)
}

// UnsafeMutableBufferPointer<UInt8>
// =================================
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}s22utf8_decoding_fastpath16decodeUMBPAsUTF8ySSSrys5UInt8VGF{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK-LAST: ret
public func decodeUMBPAsUTF8(_ ptr: UnsafeMutableBufferPointer<UInt8>) -> String {
return String(decoding: ptr, as: Unicode.UTF8.self)
}

// Array<UInt8>
// ============
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}decodeArrayAsUTF8{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK-LAST: ret
public func decodeArrayAsUTF8(_ ptr: [UInt8]) -> String {
return String(decoding: ptr, as: Unicode.UTF8.self)
}

// UnsafeRawBufferPointer
// ======================
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}decodeURBPAsUTF8{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK-LAST: ret
public func decodeURBPAsUTF8(_ ptr: UnsafeRawBufferPointer) -> String {
return String(decoding: ptr, as: Unicode.UTF8.self)
}

// UnsafeMutableRawBufferPointer
// =============================
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}decodeUMRBPAsUTF8{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK-LAST: ret
public func decodeUMRBPAsUTF8(_ ptr: UnsafeMutableRawBufferPointer) -> String {
return String(decoding: ptr, as: Unicode.UTF8.self)
}

// String.UTF8View
// ===============
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}decodeStringUTF8ViewAs{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK-LAST: br
public func decodeStringUTF8ViewAsUTF8(_ ptr: String.UTF8View) -> String {
return String(decoding: ptr, as: Unicode.UTF8.self)
}

// Substring.UTF8View
// ==================
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}decodeSubstringUTF8ViewAs{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK-LAST: br
public func decodeSubstringUTF8ViewAsUTF8(_ ptr: Substring.UTF8View) -> String {
return String(decoding: ptr, as: Unicode.UTF8.self)
}

// Slice<UBP>
// ==========
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}decodeUBPSliceAsUTF8{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK-LAST: br
public func decodeUBPSliceAsUTF8(_ ptr: Slice<UnsafeBufferPointer<UInt8>>) -> String {
return String(decoding: ptr, as: Unicode.UTF8.self)
}
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Could you file a bug and directly link it in the comment? Unless the test is XFAIL, I think it's better to disable the check than to test the undesired behavior. You can say something like:

// CHECK-LABEL: define swiftcc {{.*}}decodeUBPSliceAsUTF8{{.*}}
//
// ... comment linking and explaining bug, to be reenabled when fixed
// xCHECK-NOT: {{.*}} = call swiftcc {{.*}}_fromCodeUnits{{.*}}
// xCHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
//
// CHECK: ret

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I'd say checking the undesired behavior is better because the test'll tell you if it changes for the better.

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@milseman up to you which way, I did file a bug

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I'll go with @jrose-apple's suggestion, but make it a little more explicit that you're checking against current behavior rather than desired behavior. Something like:

// FIXME(https://bugs.swift.org/browse/SR-9700):  _fromUTF8Repairing instead of _fromCodeUnits.
// Currently, Slice<UBP> doesn't actually work. Swap checked function below when resolved.

And then probably link to this specific test in the bug itself, so the resolver knows where to expect a change.


// Slice<URBP>
// ===========
// CHECK-LABEL: define {{.*}}swiftcc {{.*}}decodeURBPSliceAsUTF8{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: {{.*}} = call swiftcc {{.*}} @"$sSS18_fromUTF8Repairing{{.*}}
// CHECK-NOT: _fromCodeUnits
// CHECK: ret
public func decodeURBPSliceAsUTF8(_ ptr: Slice<UnsafeBufferPointer<UInt8>>) -> String {
blackhole("foo") // otherwise it just jumps into the Slice<UBP> version
return String(decoding: ptr, as: Unicode.UTF8.self)
}