Allow BranchFolding to operate on instructions with virtual registers

[sunfish]

Summary

By observing that virtual registers don't have aliases or subregisters in the way physical registers do, BranchFolding can work on instructions with virtual registers too.

[sunfish]

Abandoning for now; see also http://reviews.llvm.org/D10913

lib/CodeGen/BranchFolding.cpp

     if (!Reg)
       continue;
     if (MO.isUse()) {
-      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
-        Uses.insert(*AI);
+      if (TargetRegisterInfo::isVirtualRegister(Reg))
+        Uses.insert(Reg);
+      else
+        for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+          Uses.insert(*AI);
     } else {
       if (!MO.isDead())
         // Don't try to hoist code in the rare case the terminator defines a

 
       // If the terminator defines a register, make sure we don't hoist
       // the instruction whose def might be clobbered by the terminator.
-      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
-        Defs.insert(*AI);
+      if (TargetRegisterInfo::isVirtualRegister(Reg))
+        Defs.insert(Reg);
+      else
+        for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+          Defs.insert(*AI);
     }
   }
 

         Uses.insert(*AI);
     } else {
       if (Uses.erase(Reg)) {
-        for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
-          Uses.erase(*SubRegs); // Use sub-registers to be conservative
+        if (TargetRegisterInfo::isVirtualRegister(Reg))
+          Uses.erase(Reg);
+        else
+          for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
+            Uses.erase(*SubRegs); // Use sub-registers to be conservative
       }
-      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
-        Defs.insert(*AI);
+      if (TargetRegisterInfo::isVirtualRegister(Reg))
+        Defs.insert(Reg);
+      else
+        for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+          Defs.insert(*AI);
     }
   }