[NFC][AssemblyWriter]Allow AssemblyWriter::printBasicBlock() to print blocks that don't have parents.

[xiaoqing_wu]

Summary

Remove the assert in AssemblyWriter::printBasicBlock() and in BasicBlock::isEntryBlock() that require blocks to have parents. Instead, have BasicBlock::isEntryBlock() return false for unattached blocks. This allows us to call these functions for blocks that are not yet added to a module which is a useful debugging capability.

[xiaoqing_wu]

This version contains the correct diff.

[jyknight]

llvm/lib/IR/AsmWriter.cpp

3849

I'd suggest to make this be:
bool IsEntryBlock = BB->getParent() && BB->isEntryBlock();
instead of modifying isEntryBlock.

[xiaoqing_wu]

Updated the patch based on review feedback.

[xiaoqing_wu]

llvm/lib/IR/AsmWriter.cpp

3849

Thanks for the suggestion.

[jyknight]

Please make sure to update the description to match the new code before committing.

[jyknight]

This was committed in fbd3bb4365e145a5033fdeea0ede978304d22d68.

llvm/lib/IR/AsmWriter.cpp

if (Arg->hasName()) {
     int Slot = Machine.getLocalSlot(Arg);
     assert(Slot != -1 && "expect argument in function here");
     Out << " %" << Slot;
   }
 }
 
 /// printBasicBlock - This member is called for each basic block in a method.
 void AssemblyWriter::printBasicBlock(const BasicBlock *BB) {
-  assert(BB && BB->getParent() && "block without parent!");
-  bool IsEntryBlock = BB->isEntryBlock();
+  bool IsEntryBlock = BB->getParent() && BB->isEntryBlock();
   if (BB->hasName()) {              // Print out the label if it exists...
     Out << "\n";
     PrintLLVMName(Out, BB->getName(), LabelPrefix);
     Out << ':';
   } else if (!IsEntryBlock) {
     Out << "\n";
     int Slot = Machine.getLocalSlot(BB);
     if (Slot != -1)