JVM_IR prefer loop with inclusive bound for unsigned integer ranges

In general, we would rather prefer a range-based for loop to look like a counter loop in Java ('for (i = start; i < end; ++i) { <BODY> }'). This corresponds to i = start; do { if (i >= end) break; <BODY> } while ( { ++i; true } ) However, HotSpot doesn't recognize Kotlin unsigned integer comparison in 'if (i >= end) break;' as a counter loop condition. Thus, the loop doesn't get optimized as a counter loop, resulting in a performance regression. If we use exclusive range-based for loop instead, then we actually use unsigned integer equality instead of unsigned integer comparison, which is Ok for HotSpot. KT-49444
2021-11-08 14:40:35 +03:00
parent a207a3e8fa
commit 271368ac53
7 changed files with 108 additions and 4 deletions
@@ -0,0 +1,76 @@
+// WITH_RUNTIME
+
+// IMPORTANT!
+// Please, when your changes cause failures in bytecodeText tests for 'for' loops,
+// examine the resulting bytecode shape carefully.
+// Range and progression-based loops generated with Kotlin compiler should be
+// as close as possible to Java counter loops ('for (int i = a; i < b; ++i) { ... }').
+// Otherwise it may result in performance regression due to missing HotSpot optimizations.
+// Run Kotlin compiler benchmarks (https://github.com/Kotlin/kotlin-benchmarks)
+// with compiler built from your changes if you are not sure.
+
+fun testUIntRangeLiteral(a: UInt): Int {
+    var s = 0
+    for (x in a .. 10u) {
+        s += x.toInt()
+    }
+    return s
+}
+
+fun testULongRangeLiteral(a: ULong): Int {
+    var s = 0
+    for (x in a .. 10u) {
+        s += x.toInt()
+    }
+    return s
+}
+
+fun testUIntUntil(a: UInt): Int {
+    var s = 0
+    for (x in a until 10u) {
+        s += x.toInt()
+    }
+    return s
+}
+
+fun testULongUntil(a: ULong): Int {
+    var s = 0
+    for (x in a until 10u) {
+        s += x.toInt()
+    }
+    return s
+}
+
+fun testUIntDownTo(a: UInt): Int {
+    var s = 0
+    for (x in a downTo 10u) {
+        s += x.toInt()
+    }
+    return s
+}
+
+fun testULongDownTo(a: ULong): Int {
+    var s = 0
+    for (x in a downTo 10u) {
+        s += x.toInt()
+    }
+    return s
+}
+
+// 0 iterator
+// 0 hasNext
+// 0 next
+// 0 getStart
+// 0 getEnd
+// 0 getFirst
+// 0 getLast
+// 0 getStep
+// 0 INVOKESTATIC kotlin/U(Int|Long).constructor-impl
+// 0 INVOKE\w+ kotlin/U(Int|Long).(un)?box-impl
+
+// JVM_IR_TEMPLATES
+// 31 ILOAD
+// 21 ISTORE
+// 6 IADD
+// 0 ISUB
+// 3 IINC