[JVM_IR] Use ifne and ifeq for integer zero comparisons.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/intrinsics/CompareTo.kt

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.resolve.jvm.JvmPrimitiveType
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodSignature
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.org.objectweb.asm.Label
+import org.jetbrains.org.objectweb.asm.Opcodes
 import org.jetbrains.org.objectweb.asm.Type
 import org.jetbrains.org.objectweb.asm.commons.InstructionAdapter
 
@@ -67,6 +68,20 @@ object CompareTo : IntrinsicMethod() {
     }
 }
 
+class IntegerZeroComparison(val op: IElementType, val a: MaterialValue): BooleanValue(a.codegen) {
+    override fun jumpIfFalse(target: Label) {
+        mv.visitJumpInsn(Opcodes.IFNE, target)
+    }
+
+    override fun jumpIfTrue(target: Label) {
+        mv.visitJumpInsn(Opcodes.IFEQ, target)
+    }
+
+    override fun discard() {
+        a.discard()
+    }
+}
+
 class BooleanComparison(val op: IElementType, val a: MaterialValue, val b: MaterialValue) : BooleanValue(a.codegen) {
     override fun jumpIfFalse(target: Label) {
         // TODO 1. get rid of the dependency; 2. take `b.type` into account.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/intrinsics/Equals.kt

@@ -14,17 +14,15 @@ import org.jetbrains.kotlin.codegen.AsmUtil.genAreEqualCall
 import org.jetbrains.kotlin.codegen.AsmUtil.isPrimitive
 import org.jetbrains.kotlin.codegen.StackValue
 import org.jetbrains.kotlin.codegen.intrinsics.IntrinsicMethods
-import org.jetbrains.kotlin.codegen.pseudoInsns.fakeAlwaysFalseIfeq
-import org.jetbrains.kotlin.codegen.pseudoInsns.fakeAlwaysTrueIfeq
 import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.ir.expressions.IrFunctionAccessExpression
 import org.jetbrains.kotlin.ir.expressions.IrStatementOrigin
-import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.classOrNull
 import org.jetbrains.kotlin.ir.types.isNullable
 import org.jetbrains.kotlin.ir.types.toKotlinType
 import org.jetbrains.kotlin.ir.util.isEnumClass
 import org.jetbrains.kotlin.ir.util.isEnumEntry
+import org.jetbrains.kotlin.ir.util.isIntegerConst
 import org.jetbrains.kotlin.ir.util.isNullConst
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.resolve.jvm.AsmTypes
@@ -97,9 +95,14 @@ class Equals(val operator: IElementType) : IntrinsicMethod() {
             MaterialValue(codegen, Type.BOOLEAN_TYPE, codegen.context.irBuiltIns.booleanType)
         } else {
             val operandType = if (!isPrimitive(leftType)) AsmTypes.OBJECT_TYPE else leftType
-            val aValue = a.accept(codegen, data).materializedAt(operandType, a.type)
-            val bValue = b.accept(codegen, data).materializedAt(operandType, b.type)
-            BooleanComparison(operator, aValue, bValue)
+            if (operandType == Type.INT_TYPE && (a.isIntegerConst(0) || b.isIntegerConst(0))) {
+                val nonZero = if (a.isIntegerConst(0)) b else a
+                IntegerZeroComparison(operator, nonZero.accept(codegen, data).materializedAt(operandType, nonZero.type))
+            } else {
+                val aValue = a.accept(codegen, data).materializedAt(operandType, a.type)
+                val bValue = b.accept(codegen, data).materializedAt(operandType, b.type)
+                BooleanComparison(operator, aValue, bValue)
+            }
         }
     }
 }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt

@@ -154,6 +154,8 @@ fun IrExpression.isTrueConst() = this is IrConst<*> && this.kind == IrConstKind.
 
 fun IrExpression.isFalseConst() = this is IrConst<*> && this.kind == IrConstKind.Boolean && this.value == false
 
+fun IrExpression.isIntegerConst(value: Int) = this is IrConst<*> && this.kind == IrConstKind.Int && this.value == value
+
 fun IrExpression.coerceToUnit(builtins: IrBuiltIns): IrExpression {
     val valueType = getKotlinType(this)
     return coerceToUnitIfNeeded(valueType, builtins)

compiler/testData/codegen/bytecodeText/when/whenZero.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// TODO KT-36841 Generate integer comparison with 0 instructions (IFNE, etc) when comparing integers with 0 in JVM_IR
-
 fun test(a: Int, b: Int, c: Int) {
     when (0) {
         a -> throw IllegalArgumentException("a is 0")