[NFC] Add debug msgs in copy value opts

Author: meg-gupta

lib/SILOptimizer/SemanticARC/CopyValueOpts.cpp

@@ -69,6 +69,9 @@ using namespace swift::semanticarc;
 // TODO: This needs a better name.
 bool SemanticARCOptVisitor::performGuaranteedCopyValueOptimization(
     CopyValueInst *cvi) {
+  LLVM_DEBUG(llvm::dbgs() << "Looking at ");
+  LLVM_DEBUG(cvi->dump());
+
   // All mandatory copy optimization is handled by CanonicalizeOSSALifetime,
   // which knows how to preserve lifetimes for debugging.
   if (ctx.onlyMandatoryOpts)
@@ -82,8 +85,11 @@ bool SemanticARCOptVisitor::performGuaranteedCopyValueOptimization(
   //
   // NOTE: We can get multiple introducers if our copy_value's operand
   // value runs through a phi or an aggregate forming instruction.
-  if (!getAllBorrowIntroducingValues(cvi->getOperand(), borrowScopeIntroducers))
+  if (!getAllBorrowIntroducingValues(cvi->getOperand(),
+                                     borrowScopeIntroducers)) {
+    LLVM_DEBUG(llvm::dbgs() << "Did not find all borrow introducers\n");
     return false;
+  }
 
   // Then go over all of our uses and see if the value returned by our copy
   // value forms a dead live range or a live range that would be dead if it was
@@ -96,6 +102,7 @@ bool SemanticARCOptVisitor::performGuaranteedCopyValueOptimization(
       lr.hasUnknownConsumingUse(ctx.assumingAtFixedPoint);
   if (hasUnknownConsumingUseState ==
       OwnershipLiveRange::HasConsumingUse_t::Yes) {
+    LLVM_DEBUG(llvm::dbgs() << "Found unknown consuming uses\n");
     return false;
   }
 
@@ -192,6 +199,8 @@ bool SemanticARCOptVisitor::performGuaranteedCopyValueOptimization(
           return !borrowScope.areUsesWithinExtendedScope(
               lr.getAllConsumingUses(), nullptr);
         })) {
+      LLVM_DEBUG(llvm::dbgs() << "copy_value is extending borrow introducer "
+                                 "lifetime, bailing out\n");
       return false;
     }
   }