diff --git a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
index 7c631af490d..ea4682b2279 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
@@ -17,7 +17,6 @@
 package org.jetbrains.kotlin.types.expressions;
 
 import com.google.common.collect.Lists;
-import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.StubBasedPsiElement;
 import com.intellij.psi.tree.IElementType;
@@ -39,6 +38,7 @@ import org.jetbrains.kotlin.incremental.KotlinLookupLocation;
 import org.jetbrains.kotlin.lexer.KtKeywordToken;
 import org.jetbrains.kotlin.lexer.KtTokens;
 import org.jetbrains.kotlin.name.Name;
+import org.jetbrains.kotlin.parsing.ParseUtilsKt;
 import org.jetbrains.kotlin.psi.*;
 import org.jetbrains.kotlin.psi.psiUtil.PsiUtilsKt;
 import org.jetbrains.kotlin.psi.psiUtil.ReservedCheckingKt;
@@ -75,12 +75,9 @@ import org.jetbrains.kotlin.types.expressions.typeInfoFactory.TypeInfoFactoryKt;
 import org.jetbrains.kotlin.types.expressions.unqualifiedSuper.UnqualifiedSuperKt;
 import org.jetbrains.kotlin.util.OperatorNameConventions;
 
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 import static org.jetbrains.kotlin.diagnostics.Errors.*;
 import static org.jetbrains.kotlin.lexer.KtTokens.*;
@@ -237,8 +234,6 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
         return components.dataFlowAnalyzer.createCompileTimeConstantTypeInfo(compileTimeConstant, expression, context);
     }
 
-    private static final Pattern FP_LITERAL_PARTS = Pattern.compile("(?:([_\\d]*)\\.?([_\\d]*)e?[+-]?([_\\d]*))[f]?");
-
     private void checkUnderscores(
             @NotNull KtConstantExpression expression,
             @NotNull IElementType elementType,
@@ -254,30 +249,8 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
             return;
         }
 
-        List<String> parts;
-
-        if (elementType == KtNodeTypes.INTEGER_CONSTANT) {
-            int start = 0;
-            int end = expression.getText().length();
-            if (text.startsWith("0x") || text.startsWith("0b")) start += 2;
-            if (StringUtil.endsWithChar(text, 'l')) --end;
-            parts = Collections.singletonList(text.substring(start, end));
-        }
-        else {
-            Matcher matcher = FP_LITERAL_PARTS.matcher(text);
-            parts = new ArrayList<>();
-            if (matcher.matches()) {
-                for (int i = 0; i < matcher.groupCount(); i++) {
-                    parts.add(matcher.group(i + 1));
-                }
-            }
-        }
-
-        for (String part : parts) {
-            if (part != null && (part.startsWith("_") || part.endsWith("_"))) {
-                context.trace.report(Errors.ILLEGAL_UNDERSCORE.on(expression));
-                return;
-            }
+        if (ParseUtilsKt.hasIllegalUnderscore(expression.getText(), elementType)) {
+            context.trace.report(Errors.ILLEGAL_UNDERSCORE.on(expression));
         }
     }
 
diff --git a/compiler/psi/src/org/jetbrains/kotlin/parsing/ParseUtils.kt b/compiler/psi/src/org/jetbrains/kotlin/parsing/ParseUtils.kt
index f3d716de258..983a7b610b7 100644
--- a/compiler/psi/src/org/jetbrains/kotlin/parsing/ParseUtils.kt
+++ b/compiler/psi/src/org/jetbrains/kotlin/parsing/ParseUtils.kt
@@ -10,6 +10,22 @@ import com.intellij.util.text.LiteralFormatUtil
 import org.jetbrains.kotlin.KtNodeTypes
 import org.jetbrains.kotlin.utils.extractRadix
 
+private val FP_LITERAL_PARTS = "(?:([_\\d]*)\\.?([_\\d]*)e?[+-]?([_\\d]*))[f]?".toRegex()
+
+fun hasIllegalUnderscore(text: String, elementType: IElementType): Boolean {
+    val parts: List<String?> = if (elementType === KtNodeTypes.INTEGER_CONSTANT) {
+        var start = 0
+        var end: Int = text.length
+        if (text.startsWith("0x", ignoreCase = true) || text.startsWith("0b", ignoreCase = true)) start += 2
+        if (text.endsWith('l', ignoreCase = true)) --end
+        listOf(text.substring(start, end))
+    } else {
+        FP_LITERAL_PARTS.findAll(text).flatMap { it.groupValues }.toList()
+    }
+
+    return parts.any { it != null && (it.startsWith("_") || it.endsWith("_")) }
+}
+
 fun hasLongSuffix(text: String) = text.endsWith('l') || text.endsWith('L')
 fun hasUnsignedSuffix(text: String) = text.endsWith('u') || text.endsWith('U')
 fun hasUnsignedLongSuffix(text: String) =