Add new tests for step progressions and fix existing tests.

compiler/testData/codegen/bytecodeText/forLoop/primitiveProgression.kt

@@ -2,11 +2,61 @@ fun f() {
     for (i in 0..5 step 2) {
     }
 
-    for (i in 5 downTo 1 step 1) { // suppress optimized code generation for 'for-in-downTo'
+    // JVM non-IR: `step 1` suppresses optimized code generation for 'for-in-downTo'
+    // JVM IR: No getProgressionLastElement() call required for `step 1`, equivalent to `5 downTo 1`
+    for (i in 5 downTo 1 step 1) {
     }
 }
 
+// JVM non-IR does NOT specifically handle "step" progressions. The stepped progressions in the above code are constructed and their
+// first/last/step properties are retrieved.
+// JVM IR has an optimized handler for "step" progressions and elides the construction of the stepped progressions.
+//
+// Expected lowered form of `for (i in 0..5 step 2)`:
+//
+//   // Standard form of loop over progression
+//   var inductionVar = 0
+//   val last = getProgressionLastElement(0, 5, 2)
+//   val step = 2
+//   if (inductionVar <= last) {
+//     // Loop is not empty
+//     do {
+//       val i = inductionVar
+//       inductionVar += step
+//       // Loop body
+//     } while (i != last)
+//   }
+//
+// Expected lowered form of `for (i in 5 downTo 1 step 1)`:
+//
+//   // Standard form of loop over progression
+//   var inductionVar = 5
+//   val last = 1
+//   val step = -1
+//   if (last <= inductionVar) {   // Optimized out in bytecode
+//     // Loop is not empty
+//     do {
+//       val i = inductionVar
+//       inductionVar += step
+//       // Loop body
+//     } while (last <= inductionVar)
+//   }
+
 // 0 iterator
+
+// JVM_TEMPLATES
 // 2 getFirst
 // 2 getLast
-// 2 getStep
+// 2 getStep
+
+// JVM_IR_TEMPLATES
+// 0 getStart
+// 0 getEnd
+// 0 getFirst
+// 0 getLast
+// 0 getStep
+// 1 IF_ICMPGT
+// 1 IF_ICMPNE
+// 1 IF_ICMPLE
+// 3 IF
+// 1 INVOKESTATIC kotlin/internal/ProgressionUtilKt.getProgressionLastElement \(III\)I