From cc5b5bff2eb765cd5033274df56b4a4f9f7608ff Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Mon, 8 Jun 2020 11:13:20 +0300
Subject: [PATCH] compiler: emit NOTEQUAL only for numbers

Dispatch based on types similarly to EQUAL.
---
 pkg/compiler/codegen.go     | 40 ++++++++++++++++++-------------------
 pkg/compiler/struct_test.go | 23 +++++++++++++++++++++
 2 files changed, 43 insertions(+), 20 deletions(-)

diff --git a/pkg/compiler/codegen.go b/pkg/compiler/codegen.go
index 7c4cfa30b..801937d32 100644
--- a/pkg/compiler/codegen.go
+++ b/pkg/compiler/codegen.go
@@ -470,7 +470,6 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 	case *ast.SwitchStmt:
 		ast.Walk(c, n.Tag)
 
-		eqOpcode := c.getEqualityOpcode(n.Tag)
 		switchEnd, label := c.generateLabel(labelEnd)
 
 		lastSwitch := c.currentSwitch
@@ -490,7 +489,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 				for j := range cc.List {
 					emit.Opcode(c.prog.BinWriter, opcode.DUP)
 					ast.Walk(c, cc.List[j])
-					emit.Opcode(c.prog.BinWriter, eqOpcode)
+					c.emitEquality(n.Tag, token.EQL)
 					if j == l-1 {
 						emit.Jmp(c.prog.BinWriter, opcode.JMPIFNOT, lEnd)
 					} else {
@@ -630,19 +629,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 					c.prog.Err = errors.New("comparison with `nil` is not supported, use `len(..) == 0` instead")
 					return nil
 				}
-				if n.Op == token.EQL {
-					// VM has separate opcodes for number and string equality
-					op := c.getEqualityOpcode(n.X)
-					emit.Opcode(c.prog.BinWriter, op)
-				} else {
-					// VM has separate opcodes for number and string equality
-					if isStringType(c.typeInfo.Types[n.X].Type) {
-						emit.Opcode(c.prog.BinWriter, opcode.EQUAL)
-						emit.Opcode(c.prog.BinWriter, opcode.NOT)
-					} else {
-						emit.Opcode(c.prog.BinWriter, opcode.NUMNOTEQUAL)
-					}
-				}
+				c.emitEquality(n.X, n.Op)
 			default:
 				c.convertToken(n.Op)
 			}
@@ -988,13 +975,26 @@ func (c *codegen) getLabelOffset(typ labelOffsetType, name string) uint16 {
 	return c.labels[labelWithType{name: name, typ: typ}]
 }
 
-func (c *codegen) getEqualityOpcode(expr ast.Expr) opcode.Opcode {
+func (c *codegen) emitEquality(expr ast.Expr, op token.Token) {
 	t, ok := c.typeInfo.Types[expr].Type.Underlying().(*types.Basic)
-	if ok && t.Info()&types.IsNumeric != 0 {
-		return opcode.NUMEQUAL
+	isNum := ok && t.Info()&types.IsNumeric != 0
+	switch op {
+	case token.EQL:
+		if isNum {
+			emit.Opcode(c.prog.BinWriter, opcode.NUMEQUAL)
+		} else {
+			emit.Opcode(c.prog.BinWriter, opcode.EQUAL)
+		}
+	case token.NEQ:
+		if isNum {
+			emit.Opcode(c.prog.BinWriter, opcode.NUMNOTEQUAL)
+		} else {
+			emit.Opcode(c.prog.BinWriter, opcode.EQUAL)
+			emit.Opcode(c.prog.BinWriter, opcode.NOT)
+		}
+	default:
+		panic("invalid token in emitEqual()")
 	}
-
-	return opcode.EQUAL
 }
 
 // getByteArray returns byte array value from constant expr.
diff --git a/pkg/compiler/struct_test.go b/pkg/compiler/struct_test.go
index fad15b423..58f685087 100644
--- a/pkg/compiler/struct_test.go
+++ b/pkg/compiler/struct_test.go
@@ -1,6 +1,7 @@
 package compiler_test
 
 import (
+	"fmt"
 	"math/big"
 	"testing"
 
@@ -366,3 +367,25 @@ var structTestCases = []testCase{
 func TestStructs(t *testing.T) {
 	runTestCases(t, structTestCases)
 }
+
+func TestStructCompare(t *testing.T) {
+	srcTmpl := `package testcase
+	type T struct { f int }
+	func Main() int {
+		a := T{f: %d}
+		b := T{f: %d}
+		if a != b {
+			return 2
+		}
+		return 1
+	}`
+	t.Run("Equal", func(t *testing.T) {
+		src := fmt.Sprintf(srcTmpl, 4, 4)
+		eval(t, src, big.NewInt(1))
+	})
+	t.Run("NotEqual", func(t *testing.T) {
+		src := fmt.Sprintf(srcTmpl, 4, 5)
+		eval(t, src, big.NewInt(2))
+	})
+
+}