1 files changed, 101 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/compare/compare_test.go b/src/cmd/compile/internal/compare/compare_test.go
new file mode 100644
index 0000000..2f76165
--- /dev/null
+++ b/src/cmd/compile/internal/compare/compare_test.go
@@ -0,0 +1,101 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package compare
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/obj"
+	"cmd/internal/src"
+	"cmd/internal/sys"
+	"testing"
+)
+
+type typefn func() *types.Type
+
+func init() {
+	// These are the few constants that need to be initialized in order to use
+	// the types package without using the typecheck package by calling
+	// typecheck.InitUniverse() (the normal way to initialize the types package).
+	types.PtrSize = 8
+	types.RegSize = 8
+	types.MaxWidth = 1 << 50
+	typecheck.InitUniverse()
+	base.Ctxt = &obj.Link{Arch: &obj.LinkArch{Arch: &sys.Arch{Alignment: 1, CanMergeLoads: true}}}
+}
+
+func TestEqStructCost(t *testing.T) {
+	repeat := func(n int, typ *types.Type) []*types.Type {
+		typs := make([]*types.Type, n)
+		for i := range typs {
+			typs[i] = typ
+		}
+		return typs
+	}
+
+	tt := []struct {
+		name             string
+		cost             int64
+		nonMergeLoadCost int64
+		fieldTypes       []*types.Type
+	}{
+		{"struct without fields", 0, 0, nil},
+		{"struct with 1 byte field", 1, 1, repeat(1, types.ByteType)},
+		{"struct with 8 byte fields", 1, 8, repeat(8, types.ByteType)},
+		{"struct with 16 byte fields", 2, 16, repeat(16, types.ByteType)},
+		{"struct with 32 byte fields", 4, 32, repeat(32, types.ByteType)},
+		{"struct with 2 int32 fields", 1, 2, repeat(2, types.Types[types.TINT32])},
+		{"struct with 2 int32 fields and 1 int64", 2, 3,
+			[]*types.Type{
+				types.Types[types.TINT32],
+				types.Types[types.TINT32],
+				types.Types[types.TINT64],
+			},
+		},
+		{"struct with 1 int field and 1 string", 3, 3,
+			[]*types.Type{
+				types.Types[types.TINT64],
+				types.Types[types.TSTRING],
+			},
+		},
+		{"struct with 2 strings", 4, 4, repeat(2, types.Types[types.TSTRING])},
+		{"struct with 1 large byte array field", 26, 101,
+			[]*types.Type{
+				types.NewArray(types.Types[types.TUINT16], 101),
+			},
+		},
+		{"struct with string array field", 4, 4,
+			[]*types.Type{
+				types.NewArray(types.Types[types.TSTRING], 2),
+			},
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			fields := make([]*types.Field, len(tc.fieldTypes))
+			for i, ftyp := range tc.fieldTypes {
+				fields[i] = types.NewField(src.NoXPos, typecheck.LookupNum("f", i), ftyp)
+			}
+			typ := types.NewStruct(fields)
+			types.CalcSize(typ)
+
+			want := tc.cost
+			base.Ctxt.Arch.CanMergeLoads = true
+			actual := EqStructCost(typ)
+			if actual != want {
+				t.Errorf("CanMergeLoads=true EqStructCost(%v) = %d, want %d", typ, actual, want)
+			}
+
+			base.Ctxt.Arch.CanMergeLoads = false
+			want = tc.nonMergeLoadCost
+			actual = EqStructCost(typ)
+			if actual != want {
+				t.Errorf("CanMergeLoads=false EqStructCost(%v) = %d, want %d", typ, actual, want)
+			}
+		})
+	}
+}