benchmarks: add some blackHole calls to prevent the optimizer removing important parts of a benchmark

Author: eeckstein

benchmark/single-source/ArrayOfGenericPOD.swift

@@ -40,7 +40,7 @@ class RefArray<T> {
 // elements should be a nop.
 @inline(never)
 func genEnumArray() {
-  _ = RefArray<Int?>(3)
+  blackHole(RefArray<Int?>(3))
   // should be a nop
 }
 
@@ -53,7 +53,7 @@ struct S<T> {
 }
 @inline(never)
 func genStructArray() {
-  _ = RefArray<S<Int>>(S(x:3, y:4))
+  blackHole(RefArray<S<Int>>(S(x:3, y:4)))
   // should be a nop
 }
 

benchmark/single-source/ArrayOfGenericRef.swift

@@ -47,7 +47,7 @@ class GenericRef<T> : Constructible {
 // Reference to a POD class.
 @inline(never)
 func genPODRefArray() {
-  _ = ConstructibleArray<GenericRef<Int>>(3)
+  blackHole(ConstructibleArray<GenericRef<Int>>(3))
   // should be a nop
 }
 
@@ -57,7 +57,7 @@ class Dummy {}
 @inline(never)
 func genCommonRefArray() {
   let d = Dummy()
-  _ = ConstructibleArray<GenericRef<Dummy>>(d)
+  blackHole(ConstructibleArray<GenericRef<Dummy>>(d))
   // should be a nop
 }
 
@@ -74,7 +74,7 @@ class RefArray<T> {
 @inline(never)
 func genRefEnumArray() {
   let d = Dummy()
-  _ = RefArray<Dummy?>(d)
+  blackHole(RefArray<Dummy?>(d))
   // should be a nop
 }
 
@@ -88,7 +88,7 @@ struct GenericVal<T> : Constructible {
 @inline(never)
 func genRefStructArray() {
   let d = Dummy()
-  _ = ConstructibleArray<GenericVal<Dummy>>(d)
+  blackHole(ConstructibleArray<GenericVal<Dummy>>(d))
   // should be a nop
 }
 

benchmark/single-source/ArrayOfPOD.swift

@@ -33,7 +33,7 @@ class RefArray<T> {
 
 @inline(never)
 func genIntArray() {
-  _ = RefArray<Int>(3, count:200_000)
+  blackHole(RefArray<Int>(3, count:200_000))
   // should be a nop
 }
 
@@ -45,7 +45,7 @@ enum PODEnum {
 
 @inline(never)
 func genEnumArray() {
-  _ = RefArray<PODEnum>(PODEnum.Some(3))
+  blackHole(RefArray<PODEnum>(PODEnum.Some(3)))
   // should be a nop
 }
 
@@ -55,7 +55,7 @@ struct S {
 }
 @inline(never)
 func genStructArray() {
-  _ = RefArray<S>(S(x:3, y:4))
+  blackHole(RefArray<S>(S(x:3, y:4)))
   // should be a nop
 }
 

benchmark/single-source/ArrayOfRef.swift

@@ -48,7 +48,7 @@ class POD : Constructible {
 
 @inline(never)
 func genPODRefArray() {
-  _ = ConstructibleArray<POD>(3)
+  blackHole(ConstructibleArray<POD>(3))
   // should be a nop
 }
 
@@ -64,7 +64,7 @@ class CommonRef : Constructible {
 @inline(never)
 func genCommonRefArray() {
   let d = Dummy()
-  _ = ConstructibleArray<CommonRef>(d)
+  blackHole(ConstructibleArray<CommonRef>(d))
   // should be a nop
 }
 
@@ -85,7 +85,7 @@ class RefArray<T> {
 @inline(never)
 func genRefEnumArray() {
   let e = RefEnum.Some(Dummy())
-  _ = RefArray<RefEnum>(e)
+  blackHole(RefArray<RefEnum>(e))
   // should be a nop
 }
 
@@ -99,7 +99,7 @@ struct S : Constructible {
 @inline(never)
 func genRefStructArray() {
   let d = Dummy()
-  _ = ConstructibleArray<S>(d)
+  blackHole(ConstructibleArray<S>(d))
   // should be a nop
 }
 

benchmark/single-source/RemoveWhere.swift

@@ -115,9 +115,9 @@ let ints = Array(0..<n)
 let str = String(repeating: "A very long ASCII string.", count: n/50)
 
 func buildWorkload() {
-  _ = strings.count
-  _ = ints.count
-  _ = str.count
+  blackHole(strings)
+  blackHole(ints)
+  blackHole(str)
 }
 
 

benchmark/single-source/SequenceAlgos.swift

@@ -64,11 +64,11 @@ let y = AnySequence(0..<n)
 let s = sequence(first: 0, next: { $0 < n&-1 ? $0&+1 : nil})
 
 func buildWorkload() {
-  _ = l.makeIterator()
-  _ = c.makeIterator()
-  _ = a.makeIterator()
-  _ = y.makeIterator()
-  _ = s.makeIterator()
+  blackHole(l.makeIterator())
+  blackHole(c.makeIterator())
+  blackHole(a.makeIterator())
+  blackHole(y.makeIterator())
+  blackHole(s.makeIterator())
 }
 
 func benchmarkEquatableSequenceAlgos<S: Sequence>(s: S, n: Int) where S.Element == Int, S: Equatable {