2 files changed, 21 insertions, 5 deletions
diff --git a/utils/TableGen/CodeGenRegisters.cpp b/utils/TableGen/CodeGenRegisters.cpp
index 499292a196..797c31a934 100644
--- a/utils/TableGen/CodeGenRegisters.cpp
+++ b/utils/TableGen/CodeGenRegisters.cpp
@@ -108,6 +108,15 @@ void CodeGenRegister::buildObjectGraph(CodeGenRegBank &RegBank) {
   // This is used by computeSecondarySubRegs() to find candidates.
   if (CoveredBySubRegs && !ExplicitSubRegs.empty())
     ExplicitSubRegs.front()->LeadingSuperRegs.push_back(this);
+
+  // Add ad hoc alias links. This is a symmetric relationship betwen two
+  // registers, so build a symmetric graph by adding links in both ends.
+  std::vector<Record*> Aliases = TheDef->getValueAsListOfDefs("Aliases");
+  for (unsigned i = 0, e = Aliases.size(); i != e; ++i) {
+    CodeGenRegister *Reg = RegBank.getReg(Aliases[i]);
+    ExplicitAliases.push_back(Reg);
+    Reg->ExplicitAliases.push_back(this);
+  }
 }
 
 const std::string &CodeGenRegister::getName() const {
@@ -1529,16 +1538,13 @@ computeOverlaps(std::map<const CodeGenRegister*, CodeGenRegister::Set> &Map) {
     Overlaps.insert(Supers.begin(), Supers.end());
 
     // Form symmetrical relations from the special Aliases[] lists.
-    std::vector<Record*> RegList = Reg->TheDef->getValueAsListOfDefs("Aliases");
+    ArrayRef<CodeGenRegister*> RegList = Reg->getExplicitAliases();
     for (unsigned i2 = 0, e2 = RegList.size(); i2 != e2; ++i2) {
-      CodeGenRegister *Reg2 = getReg(RegList[i2]);
-      CodeGenRegister::Set &Overlaps2 = Map[Reg2];
+      CodeGenRegister *Reg2 = RegList[i2];
       const CodeGenRegister::SuperRegList &Supers2 = Reg2->getSuperRegs();
       // Reg overlaps Reg2 which implies it overlaps supers(Reg2).
       Overlaps.insert(Reg2);
       Overlaps.insert(Supers2.begin(), Supers2.end());
-      Overlaps2.insert(Reg);
-      Overlaps2.insert(Supers.begin(), Supers.end());
     }
   }
 
diff --git a/utils/TableGen/CodeGenRegisters.h b/utils/TableGen/CodeGenRegisters.h
index 7e2c07ee58..491a91667a 100644
--- a/utils/TableGen/CodeGenRegisters.h
+++ b/utils/TableGen/CodeGenRegisters.h
@@ -142,6 +142,13 @@ namespace llvm {
       return SuperRegs;
     }
 
+    // Get the list of ad hoc aliases. The graph is symmetric, so the list
+    // contains all registers in 'Aliases', and all registers that mention this
+    // register in 'Aliases'.
+    ArrayRef<CodeGenRegister*> getExplicitAliases() const {
+      return ExplicitAliases;
+    }
+
     // Get the topological signature of this register. This is a small integer
     // less than RegBank.getNumTopoSigs(). Registers with the same TopoSig have
     // identical sub-register structure. That is, they support the same set of
@@ -191,6 +198,9 @@ namespace llvm {
     SmallVector<CodeGenSubRegIndex*, 8> ExplicitSubRegIndices;
     SmallVector<CodeGenRegister*, 8> ExplicitSubRegs;
 
+    // Explicit ad hoc aliases, symmetrized to form an undirected graph.
+    SmallVector<CodeGenRegister*, 8> ExplicitAliases;
+
     // Super-registers where this is the first explicit sub-register.
     SuperRegList LeadingSuperRegs;