[WASM] When expressions optimisations for String and Int constant cases

2022-07-14 13:04:45 +02:00
parent fff6b16483
commit 95396eb61a
11 changed files with 742 additions and 76 deletions
@@ -0,0 +1,78 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.backend.common
+
+import org.jetbrains.kotlin.ir.expressions.*
+import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
+import org.jetbrains.kotlin.ir.types.isBoolean
+import org.jetbrains.kotlin.ir.util.dump
+import org.jetbrains.kotlin.ir.util.isElseBranch
+import org.jetbrains.kotlin.ir.util.isTrueConst
+
+object IrWhenUtils {
+// psi2ir lowers multiple cases to nested conditions. For example,
+//
+// when (subject) {
+//   a, b, c -> action
+// }
+//
+// is lowered to
+//
+// if (if (subject == a)
+//       true
+//     else
+//       if (subject == b)
+//         true
+//       else
+//         subject == c) {
+//     action
+// }
+//
+// fir2ir lowers the same to an or sequence:
+//
+// if (((subject == a) || (subject == b)) || (subject = c)) action
+//
+// @return true if the conditions are equality checks of constants.
+    fun matchConditions(ororSymbol: IrFunctionSymbol, condition: IrExpression): ArrayList<IrCall>? {
+        if (condition is IrWhen && condition.origin == IrStatementOrigin.WHEN_COMMA) {
+            assert(condition.type.isBoolean()) { "WHEN_COMMA should always be a Boolean: ${condition.dump()}" }
+
+            val candidates = ArrayList<IrCall>()
+
+            // Match the following structure:
+            //
+            // when() {
+            //   cond_1 -> true
+            //   cond_2 -> true
+            //   ...
+            //   else -> cond_N
+            // }
+            //
+            // Namely, the structure which returns true if any one of the condition is true.
+            for (branch in condition.branches) {
+                candidates += if (isElseBranch(branch)) {
+                    assert(branch.condition.isTrueConst()) { "IrElseBranch.condition should be const true: ${branch.condition.dump()}" }
+                    matchConditions(ororSymbol, branch.result) ?: return null
+                } else {
+                    if (!branch.result.isTrueConst()) return null
+                    matchConditions(ororSymbol, branch.condition) ?: return null
+                }
+            }
+            return candidates.ifEmpty { null }
+        } else if (condition is IrCall && condition.symbol == ororSymbol) {
+            val candidates = ArrayList<IrCall>()
+            for (i in 0 until condition.valueArgumentsCount) {
+                val argument = condition.getValueArgument(i)!!
+                candidates += matchConditions(ororSymbol, argument) ?: return null
+            }
+            return candidates.ifEmpty { null }
+        } else if (condition is IrCall) {
+            return arrayListOf(condition)
+        }
+
+        return null
+    }
+}