Debug Info: remove duplication of DIEs when a DIE can be shared across CUs.

We add a map in DwarfDebug to map MDNodes that are shareable across CUs to the
corresponding DIEs: MDTypeNodeToDieMap. These DIEs can be shared across CUs,
that is why we keep the maps in DwarfDebug instead of CompileUnit.

We make the assumption that if a DIE is not added to an owner yet, we assume
it belongs to the current CU. Since DIEs for the type system are added to
their owners immediately after creation, and other DIEs belong to the current
CU, the assumption should be true.

A testing case is added to show that we only create a single DIE for a type
MDNode and we use ref_addr to refer to the type DIE.

We also add a testing case to show ref_addr relocations for non-darwin
platforms.

llvm-svn: 193779

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
index 334c1083161..69444285f4e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -115,13 +115,21 @@ DIE::~DIE() {
 /// Climb up the parent chain to get the compile unit DIE to which this DIE
 /// belongs.
 const DIE *DIE::getCompileUnit() const {
+  const DIE *Cu = getCompileUnitOrNull();
+  assert(Cu && "We should not have orphaned DIEs.");
+  return Cu;
+}
+
+/// Climb up the parent chain to get the compile unit DIE this DIE belongs
+/// to. Return NULL if DIE is not added to an owner yet.
+const DIE *DIE::getCompileUnitOrNull() const {
   const DIE *p = this;
   while (p) {
     if (p->getTag() == dwarf::DW_TAG_compile_unit)
       return p;
     p = p->getParent();
   }
-  llvm_unreachable("We should not have orphaned DIEs.");
+  return NULL;
 }
 
 DIEValue *DIE::findAttribute(uint16_t Attribute) {