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ForLoopsLowering: Use last-exclusive for-loops for optimized until

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progressions instead of decrementing "last".

#KT-41352 Fixed
This commit is contained in:
Mark Punzalan
2020-10-08 06:20:25 +00:00
committed by Alexander Udalov
parent 1adb130509
commit ccbf7cc2ee
28 changed files with 98 additions and 606 deletions
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compiler/testData/codegen/bytecodeText/forLoop/stepped/emptyUntilProgressionToMinValue.kt
Vendored
-36
View File
@@ -1,36 +0,0 @@
// TARGET_BACKEND: JVM_IR
fun box(): String {
for (i in 2 until Int.MIN_VALUE step 2) {
}
return "OK"
}
// For "until" progressions in JVM IR, there is a check that the range is not empty: upper bound != MIN_VALUE.
// When the upper bound == const MIN_VALUE, the backend can eliminate the entire loop as dead code.
// Calls to getProgressionLastElement() are still present because these happen before the eliminated loop.
//
// Expected lowered form of loop (before bytecode optimizations):
//
// // Standard form of loop over progression
// var inductionVar = 2
// val last = getProgressionLastElement(2, Int.MIN_VALUE - 1, 2) // `(Int.MIN_VALUE - 1)` underflows to Int.MAX_VALUE
// if (false && inductionVar <= last) { // `false` comes from constant folding of `Int.MIN_VALUE != Int.MIN_VALUE`
// // Loop is not empty
// do {
// val i = inductionVar
// inductionVar += 2
// // Loop body
// } while (i != last)
// }
// 0 iterator
// 0 getStart
// 0 getEnd
// 0 getFirst
// 0 getLast
// 0 getStep
// 1 INVOKESTATIC kotlin/internal/ProgressionUtilKt.getProgressionLastElement
// 0 NEW java/lang/IllegalArgumentException
// 0 ATHROW
// 0 IF
compiler/testData/codegen/bytecodeText/forLoop/stepped/untilProgressionToNonConst.kt
Vendored
-43
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@@ -1,43 +0,0 @@
// TARGET_BACKEND: JVM_IR
fun nine() = 9
fun box(): String {
for (i in 1 until nine() step 2) {
}
return "OK"
}
// For "until" progressions in JVM IR, there is a check that the range is not empty: upper bound != MIN_VALUE.
//
// Expected lowered form of loop (before bytecode optimizations):
//
// // Additional statements:
// val untilArg = nine()
// val nestedLast = untilArg - 1
//
// // Standard form of loop over progression
// var inductionVar = 1
// val last = getProgressionLastElement(1, nestedLast, 2)
// if (untilArg != Int.MIN_VALUE && inductionVar <= last) {
// // Loop is not empty
// do {
// val i = inductionVar
// inductionVar += 2
// // Loop body
// } while (i != last)
// }
// 0 iterator
// 0 getStart
// 0 getEnd
// 0 getFirst
// 0 getLast
// 0 getStep
// 1 INVOKESTATIC kotlin/internal/ProgressionUtilKt.getProgressionLastElement
// 0 NEW java/lang/IllegalArgumentException
// 1 LDC -2147483648
// 1 IF_ICMPEQ
// 1 IF_ICMPGT
// 1 IF_ICMPNE
// 3 IF