2 files changed, 13 insertions, 3 deletions
diff --git a/include/llvm/Target/TargetRegisterInfo.h b/include/llvm/Target/TargetRegisterInfo.h
index 2deede2..68460b3 100644
--- a/include/llvm/Target/TargetRegisterInfo.h
+++ b/include/llvm/Target/TargetRegisterInfo.h
@@ -21,6 +21,7 @@
 #include "llvm/CodeGen/ValueTypes.h"
 #include <cassert>
 #include <functional>
+#include <set>
 
 namespace llvm {
 
@@ -285,6 +286,7 @@ private:
   regclass_iterator RegClassBegin, RegClassEnd;   // List of regclasses
 
   int CallFrameSetupOpcode, CallFrameDestroyOpcode;
+  std::set<std::pair<unsigned, unsigned> > Subregs;
 protected:
   TargetRegisterInfo(const TargetRegisterDesc *D, unsigned NR,
                      regclass_iterator RegClassBegin,
@@ -419,9 +421,7 @@ public:
   /// isSubRegister - Returns true if regB is a sub-register of regA.
   ///
   bool isSubRegister(unsigned regA, unsigned regB) const {
-    for (const unsigned *SR = getSubRegisters(regA); *SR; ++SR)
-      if (*SR == regB) return true;
-    return false;
+    return Subregs.count(std::make_pair(regA, regB));
   }
 
   /// isSuperRegister - Returns true if regB is a super-register of regA.
diff --git a/lib/Target/TargetRegisterInfo.cpp b/lib/Target/TargetRegisterInfo.cpp
index 3f44a0c..e69496f 100644
--- a/lib/Target/TargetRegisterInfo.cpp
+++ b/lib/Target/TargetRegisterInfo.cpp
@@ -29,6 +29,16 @@ TargetRegisterInfo::TargetRegisterInfo(const TargetRegisterDesc *D, unsigned NR,
 
   CallFrameSetupOpcode   = CFSO;
   CallFrameDestroyOpcode = CFDO;
+  
+  for (unsigned i = 0; i < NumRegs; ++i) {
+    const TargetRegisterDesc* CurrReg = Desc + i;
+    
+    // Initialize the Subregs set, which stores pairs (a, b) where
+    // b is a subreg of a.
+    if (CurrReg->SubRegs)
+      for (const unsigned* CurrSR = CurrReg->SubRegs; *CurrSR; ++CurrSR)
+        Subregs.insert(std::make_pair(i, *CurrSR));
+  }
 }
 
 TargetRegisterInfo::~TargetRegisterInfo() {}