math_test.go

Documentation: runtime/internal/math

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package math_test
     6  
     7  import (
     8  	. "runtime/internal/math"
     9  	"testing"
    10  )
    11  
    12  const (
    13  	UintptrSize = 32 << (^uintptr(0) >> 63)
    14  )
    15  
    16  type mulUintptrTest struct {
    17  	a        uintptr
    18  	b        uintptr
    19  	overflow bool
    20  }
    21  
    22  var mulUintptrTests = []mulUintptrTest{
    23  	{0, 0, false},
    24  	{1000, 1000, false},
    25  	{MaxUintptr, 0, false},
    26  	{MaxUintptr, 1, false},
    27  	{MaxUintptr / 2, 2, false},
    28  	{MaxUintptr / 2, 3, true},
    29  	{MaxUintptr, 10, true},
    30  	{MaxUintptr, 100, true},
    31  	{MaxUintptr / 100, 100, false},
    32  	{MaxUintptr / 1000, 1001, true},
    33  	{1<<(UintptrSize/2) - 1, 1<<(UintptrSize/2) - 1, false},
    34  	{1 << (UintptrSize / 2), 1 << (UintptrSize / 2), true},
    35  	{MaxUintptr >> 32, MaxUintptr >> 32, false},
    36  	{MaxUintptr, MaxUintptr, true},
    37  }
    38  
    39  func TestMulUintptr(t *testing.T) {
    40  	for _, test := range mulUintptrTests {
    41  		a, b := test.a, test.b
    42  		for i := 0; i < 2; i++ {
    43  			mul, overflow := MulUintptr(a, b)
    44  			if mul != a*b || overflow != test.overflow {
    45  				t.Errorf("MulUintptr(%v, %v) = %v, %v want %v, %v",
    46  					a, b, mul, overflow, a*b, test.overflow)
    47  			}
    48  			a, b = b, a
    49  		}
    50  	}
    51  }
    52  
    53  var SinkUintptr uintptr
    54  var SinkBool bool
    55  
    56  var x, y uintptr
    57  
    58  func BenchmarkMulUintptr(b *testing.B) {
    59  	x, y = 1, 2
    60  	b.Run("small", func(b *testing.B) {
    61  		for i := 0; i < b.N; i++ {
    62  			var overflow bool
    63  			SinkUintptr, overflow = MulUintptr(x, y)
    64  			if overflow {
    65  				SinkUintptr = 0
    66  			}
    67  		}
    68  	})
    69  	x, y = MaxUintptr, MaxUintptr-1
    70  	b.Run("large", func(b *testing.B) {
    71  		for i := 0; i < b.N; i++ {
    72  			var overflow bool
    73  			SinkUintptr, overflow = MulUintptr(x, y)
    74  			if overflow {
    75  				SinkUintptr = 0
    76  			}
    77  		}
    78  	})
    79  }
    80
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