[llvm-commits] [llvm] r151773 - /llvm/trunk/utils/TableGen/RegisterInfoEmitter.cpp

[Benjamin Kramer]

Author: d0k
Date: Wed Feb 29 17:46:50 2012
New Revision: 151773

URL: http://llvm.org/viewvc/llvm-project?rev=151773&view=rev
Log:
Implement getSubRegIndex as a linear search on the SubRegTable instead of using a big switch.

- The search bounds are constant, in the worst case (ARM target) it will scan over 30 uint16_ts.
- This method isn't very hot, I had problems finding a testcase where it's called more than a dozen of times (no perf impact).

Modified:
    llvm/trunk/utils/TableGen/RegisterInfoEmitter.cpp

Modified: llvm/trunk/utils/TableGen/RegisterInfoEmitter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/utils/TableGen/RegisterInfoEmitter.cpp?rev=151773&r1=151772&r2=151773&view=diff
==============================================================================
--- llvm/trunk/utils/TableGen/RegisterInfoEmitter.cpp (original)
+++ llvm/trunk/utils/TableGen/RegisterInfoEmitter.cpp Wed Feb 29 17:46:50 2012
@@ -774,21 +774,13 @@
     OS << "  return 0;\n}\n\n";
 
   OS << "unsigned " << ClassName
-     << "::getSubRegIndex(unsigned RegNo, unsigned SubRegNo) const {\n"
-     << "  switch (RegNo) {\n"
-     << "  default:\n    return 0;\n";
-   for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
-     const CodeGenRegister::SubRegMap &SRM = Regs[i]->getSubRegs();
-     if (SRM.empty())
-       continue;
-    OS << "  case " << getQualifiedName(Regs[i]->TheDef) << ":\n";
-    for (CodeGenRegister::SubRegMap::const_iterator ii = SRM.begin(),
-         ie = SRM.end(); ii != ie; ++ii)
-      OS << "    if (SubRegNo == " << getQualifiedName(ii->second->TheDef)
-         << ")  return " << ii->first->getQualifiedName() << ";\n";
-    OS << "    return 0;\n";
+     << "::getSubRegIndex(unsigned RegNo, unsigned SubRegNo) const {\n";
+  if (SubRegIndices.size()) {
+    OS << "  for (unsigned I = 0; I != array_lengthof("
+       << TargetName << "SubRegTable[0]); ++I)\n"
+       << "    if (" << TargetName << "SubRegTable[RegNo - 1][I] == SubRegNo)\n"
+       << "      return I + 1;\n";
   }
-  OS << "  };\n";
   OS << "  return 0;\n";
   OS << "}\n\n";