Add MCRI::getNumSubRegIndices() and start checking SubRegIndex ranges.

Apparently, NumSubRegIndices was completely unused before. Adjust it by
one to include the null subreg index, just like getNumRegs() includes
the null register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163628 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCRegisterInfo.h

@@ -333,6 +333,13 @@ public:
     return NumRegs;
   }
 
+  /// getNumSubRegIndices - Return the number of sub-register indices
+  /// understood by the target. Index 0 is reserved for the no-op sub-register,
+  /// while 1 to getNumSubRegIndices() - 1 represent real sub-registers.
+  unsigned getNumSubRegIndices() const {
+    return NumSubRegIndices;
+  }
+
   /// getNumRegUnits - Return the number of (native) register units in the
   /// target. Register units are numbered from 0 to getNumRegUnits() - 1. They
   /// can be accessed through MCRegUnitIterator defined below.

include/llvm/Target/TargetRegisterInfo.h

@@ -327,7 +327,8 @@ public:
   /// getSubRegIndexName - Return the human-readable symbolic target-specific
   /// name for the specified SubRegIndex.
   const char *getSubRegIndexName(unsigned SubIdx) const {
-    assert(SubIdx && "This is not a subregister index");
+    assert(SubIdx && SubIdx < getNumSubRegIndices() &&
+           "This is not a subregister index");
     return SubRegIndexNames[SubIdx-1];
   }
 

lib/MC/MCRegisterInfo.cpp

@@ -24,6 +24,8 @@ unsigned MCRegisterInfo::getMatchingSuperReg(unsigned Reg, unsigned SubIdx,
 }
 
 unsigned MCRegisterInfo::getSubReg(unsigned Reg, unsigned Idx) const {
+  assert(Idx && Idx < getNumSubRegIndices() &&
+         "This is not a subregister index");
   // Get a pointer to the corresponding SubRegIndices list. This list has the
   // name of each sub-register in the same order as MCSubRegIterator.
   const uint16_t *SRI = SubRegIndices + get(Reg).SubRegIndices;
@@ -34,6 +36,7 @@ unsigned MCRegisterInfo::getSubReg(unsigned Reg, unsigned Idx) const {
 }
 
 unsigned MCRegisterInfo::getSubRegIndex(unsigned Reg, unsigned SubReg) const {
+  assert(SubReg && SubReg < getNumRegs() && "This is not a register");
   // Get a pointer to the corresponding SubRegIndices list. This list has the
   // name of each sub-register in the same order as MCSubRegIterator.
   const uint16_t *SRI = SubRegIndices + get(Reg).SubRegIndices;

utils/TableGen/RegisterInfoEmitter.cpp

@@ -770,7 +770,7 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
      << TargetName << "RegDiffLists, "
      << TargetName << "RegStrings, "
      << TargetName << "SubRegIdxLists, "
-     << SubRegIndices.size() << ",\n"
+     << (SubRegIndices.size() + 1) << ",\n"
      << "  " << TargetName << "RegEncodingTable);\n\n";
 
   EmitRegMapping(OS, Regs, false);
@@ -1131,7 +1131,7 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
      << "                     " << TargetName << "RegDiffLists,\n"
      << "                     " << TargetName << "RegStrings,\n"
      << "                     " << TargetName << "SubRegIdxLists,\n"
-     << "                     " << SubRegIndices.size() << ",\n"
+     << "                     " << SubRegIndices.size() + 1 << ",\n"
      << "                     " << TargetName << "RegEncodingTable);\n\n";
 
   EmitRegMapping(OS, Regs, true);