Preserve all metadata when removing dead arguments

[llvmbot]

Bugzilla Link	11042
Version	trunk
OS	All
Reporter	LLVM Bugzilla Contributor

Extended Description

At around Line 257 and Line 835, DAE preserves debug locations after removing the dead arguments, by copying the debug location from the old call to the new call. Should we do the same thing for other metadata (e.g. customized metadata) as well? Would it break anything?

Btw, this issue appears in LLVM 2.9 and some earlier versions as well.

Proposed patch:
Index: lib/Transforms/IPO/DeadArgumentElimination.cpp

--- lib/Transforms/IPO/DeadArgumentElimination.cpp (revision 140827)
+++ lib/Transforms/IPO/DeadArgumentElimination.cpp (working copy)
@@ -254,7 +254,14 @@
if (cast(Call)->isTailCall())
cast(New)->setTailCall();
}

• New->setDebugLoc(Call->getDebugLoc());

• // by Jingyue

• // Copy all metadata

• if (Call->hasMetadata()) {

•  SmallVector<std::pair<unsigned, MDNode*>, 4> TheMDs;
  

•  Call->getAllMetadata(TheMDs);
  

•  for (unsigned i = 0, e = TheMDs.size(); i != e; ++i)
  

•    New->setMetadata(TheMDs[i].first, TheMDs[i].second);
  

• }

  Args.clear();

@@ -832,7 +839,14 @@
if (cast(Call)->isTailCall())
cast(New)->setTailCall();
}

• New->setDebugLoc(Call->getDebugLoc());

• // by Jingyue

• // Copy all metadata

• if (Call->hasMetadata()) {

•  SmallVector<std::pair<unsigned, MDNode*>, 4> TheMDs;
  

•  Call->getAllMetadata(TheMDs);
  

•  for (unsigned i = 0, e = TheMDs.size(); i != e; ++i)
  

•    New->setMetadata(TheMDs[i].first, TheMDs[i].second);
  

• }

  Args.clear();

[llvmbot]

What if the metadata says something like "the 3rd argument is special in this particular way"?