JVM_IR: fold constant string concatenations

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmLower.kt

@@ -105,8 +105,8 @@ val jvmPhases = namedIrFilePhase(
             tailrecPhase then
             toArrayPhase then
             jvmTypeOperatorLoweringPhase then
-            foldConstantLoweringPhase then
             flattenStringConcatenationPhase then
+            foldConstantLoweringPhase then
             jvmBuiltinOptimizationLoweringPhase then
             additionalClassAnnotationPhase then
 

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/FoldConstantLowering.kt

@@ -10,10 +10,9 @@ import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
 import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
-import org.jetbrains.kotlin.ir.expressions.IrCall
+import org.jetbrains.kotlin.ir.expressions.*
-import org.jetbrains.kotlin.ir.expressions.IrConst
-import org.jetbrains.kotlin.ir.expressions.IrExpression
 import org.jetbrains.kotlin.ir.expressions.impl.IrConstImpl
+import org.jetbrains.kotlin.ir.expressions.impl.IrStringConcatenationImpl
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.fqNameWhenAvailable
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
@@ -176,6 +175,26 @@ class FoldConstantLowering(private val context: JvmBackendContext) : IrElementTr
                     else -> expression
                 }
             }
+
+            override fun visitStringConcatenation(expression: IrStringConcatenation): IrExpression {
+                expression.transformChildrenVoid(this)
+                val folded = mutableListOf<IrExpression>()
+                for (next in expression.arguments) {
+                    val last = folded.lastOrNull()
+                    when {
+                        next !is IrConst<*> -> folded += next
+                        last !is IrConst<*> -> folded += IrConstImpl.string(
+                            next.startOffset, next.endOffset, context.irBuiltIns.stringType, next.value.toString()
+                        )
+                        else -> folded[folded.size - 1] = IrConstImpl.string(
+                            last.startOffset, next.endOffset, context.irBuiltIns.stringType,
+                            last.value.toString() + next.value.toString()
+                        )
+                    }
+                }
+                return folded.singleOrNull() as? IrConst<*>
+                    ?: IrStringConcatenationImpl(expression.startOffset, expression.endOffset, expression.type, folded)
+            }
         })
     }
 }

compiler/testData/codegen/box/constants/kt9532.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: -NoConstantValueAttributeForNonConstVals
-// IGNORE_BACKEND: JVM_IR
 // TODO: muted automatically, investigate should it be ran for JS or not
 // IGNORE_BACKEND: NATIVE
 

compiler/testData/codegen/box/constants/kt9532_lv10.kt

@@ -1,5 +1,5 @@
 // !LANGUAGE: -InlineConstVals
-// IGNORE_BACKEND: JS_IR, NATIVE
+// IGNORE_BACKEND: JVM_IR, JS_IR, NATIVE
 // TODO: muted automatically, investigate should it be ran for JS or not
 // IGNORE_BACKEND: JS
 

compiler/testData/codegen/bytecodeText/stringOperations/constConcat.kt

@@ -0,0 +1,5 @@
+val s = "1" + "2" + 3 + 4L + 5.0 + 6F + '7'
+val c = "${"1"}2${3}${4L}${5.0}${6F}${'7'}"
+
+// 0 NEW java/lang/StringBuilder
+// 2 LDC "12345.06.07"

compiler/testData/codegen/bytecodeText/stringOperations/constValConcat.kt

@@ -0,0 +1,12 @@
+const val string = "2"
+const val int = 3
+const val long = 4L
+const val double = 5.0
+const val float = 6F
+const val char = '7'
+
+val s = "1" + string + int + long + double + float + char
+val c = "1$string$int$long$double$float$char"
+
+// 0 NEW java/lang/StringBuilder
+// 2 LDC "12345.06.07"

compiler/testData/codegen/bytecodeText/stringOperations/kt19037.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 const val empty = ""
 
 val test1 = ""

compiler/testData/codegen/bytecodeText/stringOperations/partiallyConstConcat.kt

@@ -0,0 +1,9 @@
+// IGNORE_BACKEND: JVM
+fun foo(a: String, b: String) {
+    val s = a + "1" + "2" + 3 + 4L + b + 5.0 + 6F + '7'
+    val c = "$a${"1"}2${3}${4L}$b${5.0}${6F}${'7'}"
+}
+
+// 2 NEW java/lang/StringBuilder
+// 2 LDC "1234"
+// 2 LDC "5.06.07"

compiler/testData/codegen/bytecodeText/whenStringOptimization/inlineStringConstInsideWhen.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 const val y = "cde"
 
 fun foo(x : String) : String {

compiler/testData/codegen/bytecodeText/whenStringOptimization/nonInlinedConst.kt

@@ -1,4 +1,5 @@
 // !LANGUAGE: -InlineConstVals
+// IGNORE_BACKEND: JVM_IR
 
 const val y = "cde"
 

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -3422,6 +3422,16 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             runTest("compiler/testData/codegen/bytecodeText/stringOperations/concat.kt");
         }
 
+        @TestMetadata("constConcat.kt")
+        public void testConstConcat() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/stringOperations/constConcat.kt");
+        }
+
+        @TestMetadata("constValConcat.kt")
+        public void testConstValConcat() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/stringOperations/constValConcat.kt");
+        }
+
         @TestMetadata("doNotAppendEmptyString.kt")
         public void testDoNotAppendEmptyString() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/stringOperations/doNotAppendEmptyString.kt");
@@ -3462,6 +3472,11 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             runTest("compiler/testData/codegen/bytecodeText/stringOperations/nullableStringPlus.kt");
         }
 
+        @TestMetadata("partiallyConstConcat.kt")
+        public void testPartiallyConstConcat() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/stringOperations/partiallyConstConcat.kt");
+        }
+
         @TestMetadata("plusAssign.kt")
         public void testPlusAssign() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/stringOperations/plusAssign.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBytecodeTextTestGenerated.java

@@ -3432,6 +3432,16 @@ public class IrBytecodeTextTestGenerated extends AbstractIrBytecodeTextTest {
             runTest("compiler/testData/codegen/bytecodeText/stringOperations/concat.kt");
         }
 
+        @TestMetadata("constConcat.kt")
+        public void testConstConcat() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/stringOperations/constConcat.kt");
+        }
+
+        @TestMetadata("constValConcat.kt")
+        public void testConstValConcat() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/stringOperations/constValConcat.kt");
+        }
+
         @TestMetadata("doNotAppendEmptyString.kt")
         public void testDoNotAppendEmptyString() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/stringOperations/doNotAppendEmptyString.kt");
@@ -3472,6 +3482,11 @@ public class IrBytecodeTextTestGenerated extends AbstractIrBytecodeTextTest {
             runTest("compiler/testData/codegen/bytecodeText/stringOperations/nullableStringPlus.kt");
         }
 
+        @TestMetadata("partiallyConstConcat.kt")
+        public void testPartiallyConstConcat() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/stringOperations/partiallyConstConcat.kt");
+        }
+
         @TestMetadata("plusAssign.kt")
         public void testPlusAssign() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/stringOperations/plusAssign.kt");