[llvm] [GlobalISel] Put legalizer rule debug behind a verbose option. (PR #138277)

[Matt Arsenault via llvm-commits]

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@@ -211,20 +217,24 @@ LegalizeActionStep LegalizeRuleSet::apply(const LegalityQuery &Query) const {
 bool LegalizeRuleSet::verifyTypeIdxsCoverage(unsigned NumTypeIdxs) const {
 #ifndef NDEBUG
   if (Rules.empty()) {
-    LLVM_DEBUG(
-        dbgs() << ".. type index coverage check SKIPPED: no rules defined\n");
+    if (VerboseVerifyLegalizerInfo)
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arsenm wrote:

These probably aren't useful in general other than the target tests for the legality rules, I think it's fine to just not print anything unless you use the flag 

https://github.com/llvm/llvm-project/pull/138277