Linker: correctly link in dbg.declare

This is a re-worked version of r174048.
Given source IR:
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !14), !dbg !15
we used to generate 
call void @llvm.dbg.declare(metadata !27, metadata !28), !dbg !29
!27 = metadata !{null}

With this patch, we will correctly generate
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !27), !dbg !28

Looking up %argc.addr in ValueMap will return null, since %argc.addr is already
correctly set up, we can use identity mapping.

rdar://problem/13089880


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174093 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 2 deletions

diff --git a/lib/Transforms/Utils/ValueMapper.cpp b/lib/Transforms/Utils/ValueMapper.cpp
index a5e164374f..b5941bdf24 100644
--- a/lib/Transforms/Utils/ValueMapper.cpp
+++ b/lib/Transforms/Utils/ValueMapper.cpp
@@ -63,14 +63,29 @@ Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM, RemapFlags Flags,
     // Check all operands to see if any need to be remapped.
     for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
       Value *OP = MD->getOperand(i);
-      if (OP == 0 || MapValue(OP, VM, Flags, TypeMapper) == OP) continue;
+      if (OP == 0) continue;
+      Value *Mapped_OP = MapValue(OP, VM, Flags, TypeMapper);
+      // Use identity map if Mapped_Op is null and we can ignore missing
+      // entries.
+      if (Mapped_OP == OP ||
+          (Mapped_OP == 0 && (Flags & RF_IgnoreMissingEntries)))
+        continue;
 
       // Ok, at least one operand needs remapping.  
       SmallVector<Value*, 4> Elts;
       Elts.reserve(MD->getNumOperands());
       for (i = 0; i != e; ++i) {
         Value *Op = MD->getOperand(i);
-        Elts.push_back(Op ? MapValue(Op, VM, Flags, TypeMapper) : 0);
+        if (Op == 0)
+          Elts.push_back(0);
+        else {
+          Value *Mapped_Op = MapValue(Op, VM, Flags, TypeMapper);
+          // Use identity map if Mapped_Op is null and we can ignore missing
+          // entries.
+          if (Mapped_Op == 0 && (Flags & RF_IgnoreMissingEntries))
+            Mapped_Op = Op;
+          Elts.push_back(Mapped_Op);
+        }
       }
       MDNode *NewMD = MDNode::get(V->getContext(), Elts);
       Dummy->replaceAllUsesWith(NewMD);