2 files changed, 23 insertions, 22 deletions

diff --git a/include/llvm/Target/TargetRegisterInfo.h b/include/llvm/Target/TargetRegisterInfo.h
index 5af90fbf8c..ceb61300ae 100644
--- a/include/llvm/Target/TargetRegisterInfo.h
+++ b/include/llvm/Target/TargetRegisterInfo.h
@@ -32,19 +32,18 @@ template<class T> class SmallVectorImpl;
 class raw_ostream;
 
 /// TargetRegisterDesc - This record contains all of the information known about
-/// a particular register.  The AliasSet field (if not null) contains a pointer
-/// to a Zero terminated array of registers that this register aliases.  This is
-/// needed for architectures like X86 which have AL alias AX alias EAX.
-/// Registers that this does not apply to simply should set this to null.
-/// The SubRegs field is a zero terminated array of registers that are
-/// sub-registers of the specific register, e.g. AL, AH are sub-registers of AX.
-/// The SuperRegs field is a zero terminated array of registers that are
+/// a particular register.  The Overlaps field contains a pointer to a zero
+/// terminated array of registers that this register aliases, starting with
+/// itself. This is needed for architectures like X86 which have AL alias AX
+/// alias EAX. The SubRegs field is a zero terminated array of registers that
+/// are sub-registers of the specific register, e.g. AL, AH are sub-registers of
+/// AX. The SuperRegs field is a zero terminated array of registers that are
 /// super-registers of the specific register, e.g. RAX, EAX, are super-registers
 /// of AX.
 ///
 struct TargetRegisterDesc {
   const char     *Name;         // Printable name for the reg (for debugging)
-  const unsigned *AliasSet;     // Register Alias Set, described above
+  const unsigned *Overlaps;     // Overlapping registers, described above
   const unsigned *SubRegs;      // Sub-register set, described above
   const unsigned *SuperRegs;    // Super-register set, described above
 };
@@ -355,7 +354,17 @@ public:
   /// terminated.
   ///
   const unsigned *getAliasSet(unsigned RegNo) const {
-    return get(RegNo).AliasSet;
+    // The Overlaps set always begins with Reg itself.
+    return get(RegNo).Overlaps + 1;
+  }
+
+  /// getOverlaps - Return a list of registers that overlap Reg, including
+  /// itself. This is the same as the alias set except Reg is included in the
+  /// list.
+  /// These are exactly the registers in { x | regsOverlap(x, Reg) }.
+  ///
+  const unsigned *getOverlaps(unsigned RegNo) const {
+    return get(RegNo).Overlaps;
   }
 
   /// getSubRegisters - Return the list of registers that are sub-registers of
diff --git a/utils/TableGen/RegisterInfoEmitter.cpp b/utils/TableGen/RegisterInfoEmitter.cpp
index ab5dd7e076..96399a4d05 100644
--- a/utils/TableGen/RegisterInfoEmitter.cpp
+++ b/utils/TableGen/RegisterInfoEmitter.cpp
@@ -777,17 +777,13 @@ void RegisterInfoEmitter::run(raw_ostream &OS) {
   delete [] AliasesHashTable;
 
   if (!RegisterAliases.empty())
-    OS << "\n\n  // Register Alias Sets...\n";
+    OS << "\n\n  // Register Overlap Lists...\n";
 
-  // Emit the empty alias list
-  OS << "  const unsigned Empty_AliasSet[] = { 0 };\n";
-  // Loop over all of the registers which have aliases, emitting the alias list
-  // to memory.
+  // Emit an overlap list for all registers.
   for (std::map<Record*, std::set<Record*>, LessRecord >::iterator
          I = RegisterAliases.begin(), E = RegisterAliases.end(); I != E; ++I) {
-    if (I->second.empty())
-      continue;
-    OS << "  const unsigned " << I->first->getName() << "_AliasSet[] = { ";
+    OS << "  const unsigned " << I->first->getName() << "_Overlaps[] = { "
+       << getQualifiedName(I->first) << ", ";
     for (std::set<Record*>::iterator ASI = I->second.begin(),
            E = I->second.end(); ASI != E; ++ASI)
       OS << getQualifiedName(*ASI) << ", ";
@@ -849,11 +845,7 @@ void RegisterInfoEmitter::run(raw_ostream &OS) {
   for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
     const CodeGenRegister &Reg = Regs[i];
     OS << "    { \"";
-    OS << Reg.getName() << "\",\t";
-    if (!RegisterAliases[Reg.TheDef].empty())
-      OS << Reg.getName() << "_AliasSet,\t";
-    else
-      OS << "Empty_AliasSet,\t";
+    OS << Reg.getName() << "\",\t" << Reg.getName() << "_Overlaps,\t";
     if (!RegisterSubRegs[Reg.TheDef].empty())
       OS << Reg.getName() << "_SubRegsSet,\t";
     else