Removed datalayout from test, improved debug message, and clarified comment.

Author: sjoerdmeijer

llvm/lib/Transforms/Scalar/LoopInterchange.cpp

@@ -101,12 +101,6 @@ static cl::opt<unsigned int> MaxLoopNestDepth(
     "loop-interchange-max-loop-nest-depth", cl::init(10), cl::Hidden,
     cl::desc("Maximum depth of loop nest considered for the transform"));
 
-// This is mainly for testing purposes, and certain tests that rely on
-// behaviour that is more difficult to trigger otherwise.
-static cl::opt<bool> SkipLoopsWithZeroBTC(
-    "loop-interchange-skip-zero-btc", cl::init(true), cl::Hidden,
-    cl::desc("Do not consider loops with a backedge taken count of 0"));
-
 // We prefer cache cost to vectorization by default.
 static cl::list<RuleTy> Profitabilities(
     "loop-interchange-profitabilities", cl::ZeroOrMore,
@@ -126,6 +120,13 @@ static cl::list<RuleTy> Profitabilities(
                           "Ignore profitability, force interchange (does not "
                           "work with other options)")));
 
+// FIXME: this option exists mainly for a couple of tests that check some
+// corner cases that is more difficult to trigger otherwise; these tests should
+// be rewritten and this option removed if possible.
+static cl::opt<bool> SkipLoopsWithZeroBTC(
+    "loop-interchange-skip-zero-btc", cl::init(true), cl::Hidden,
+    cl::desc("Do not consider loops with a backedge taken count of 0"));
+
 #ifndef NDEBUG
 static bool noDuplicateRulesAndIgnore(ArrayRef<RuleTy> Rules) {
   SmallSet<RuleTy, 4> Set;
@@ -438,7 +439,8 @@ static bool isComputableLoopNest(ScalarEvolution *SE,
     // true, isn't really a loop and we don't want to consider it as a
     // candidate.
     if (ExitCountOuter && SkipLoopsWithZeroBTC && ExitCountOuter->isZero()) {
-      LLVM_DEBUG(dbgs() << "Single iteration loop\n");
+      LLVM_DEBUG(dbgs() << "The loop back-edge isn't taken, rejecting single "
+                           "iteration loop\n");
       return false;
     }
     if (L->getNumBackEdges() != 1) {

llvm/test/Transforms/LoopInterchange/zero-btc.ll

@@ -1,8 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
 ; RUN: opt < %s -passes=loop-interchange -loop-interchange-profitabilities=ignore -cache-line-size=64 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
 
-target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
-
 ; Test case for issue: https://github.com/llvm/llvm-project/issues/163954
 
 define void @test() {