Subzero: Make -reg-use and -reg-exclude specific to register class.

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 120 matching lines @@
     }
     if (Count > 0 && Count % RegistersPerLine == 0)
       Str << "\n" << LineIndentString;
     ++Count;
     Str << getRegName(i);
   }
   if (Count)
     Str << "\n";
 }
 
+// Splits "<class>:<reg>" into "<class>" plus "<reg>".  If there is no <class>
+// component, the result is "" plus "<reg>".
+void splitToClassAndName(const IceString &RegName, IceString *SplitRegClass,
+                         IceString *SplitRegName) {
+  constexpr const char Separator[] = ":";
+  constexpr size_t SeparatorWidth = llvm::array_lengthof(Separator) - 1;
+  size_t Pos = RegName.find(Separator);
+  if (Pos == std::string::npos) {
+    *SplitRegClass = "";
+    *SplitRegName = RegName;
+  } else {
+    *SplitRegClass = RegName.substr(0, Pos);
+    *SplitRegName = RegName.substr(Pos + SeparatorWidth);
+  }
+}
+
 } // end of anonymous namespace
 
 void TargetLowering::filterTypeToRegisterSet(
     GlobalContext *Ctx, int32_t NumRegs,
     llvm::SmallBitVector TypeToRegisterSet[], size_t TypeToRegisterSetSize,
-    std::function<IceString(int32_t)> getRegName) {
-  llvm::SmallBitVector ExcludeBitSet(NumRegs);
+    std::function<IceString(int32_t)> getRegName,
+    std::function<IceString(RegClass)> getRegClassName) {
   std::vector<llvm::SmallBitVector> UseSet(TypeToRegisterSetSize,
-                                           ExcludeBitSet);
-  ExcludeBitSet.flip();
+                                           llvm::SmallBitVector(NumRegs)),
+      ExcludeSet(TypeToRegisterSetSize, llvm::SmallBitVector(NumRegs));
 
   std::unordered_map<IceString, int32_t> RegNameToIndex;
   for (int32_t RegIndex = 0; RegIndex < NumRegs; ++RegIndex)
     RegNameToIndex[getRegName(RegIndex)] = RegIndex;
 
   ClFlags::StringVector BadRegNames;
-  for (const IceString &RegName : Ctx->getFlags().getUseRestrictedRegisters()) {
-    if (!RegNameToIndex.count(RegName)) {
-      BadRegNames.push_back(RegName);
-      continue;
-    }
-    const int32_t RegIndex = RegNameToIndex[RegName];
-    for (SizeT TypeIndex = 0; TypeIndex < TypeToRegisterSetSize; ++TypeIndex)
-      UseSet[TypeIndex][RegIndex] = TypeToRegisterSet[TypeIndex][RegIndex];
-  }
 
-  for (const IceString &RegName : Ctx->getFlags().getExcludedRegisters()) {
-    if (!RegNameToIndex.count(RegName)) {
-      BadRegNames.push_back(RegName);
-      continue;
-    }
-    ExcludeBitSet[RegNameToIndex[RegName]] = false;
-  }
+  // The processRegList function iterates across the RegNames vector.  Each
+  // entry in the vector is a string of the form "<reg>" or "<class>:<reg>".
+  // The register class and register number are computed, and the corresponding
+  // bit is set in RegSet[][].  If "<class>:" is missing, then the bit is set
+  // for all classes.
+  auto processRegList =
+      [&BadRegNames, RegNameToIndex, TypeToRegisterSet, TypeToRegisterSetSize,

[Karl, 2016/01/22 17:10:54]

Why not just use [&] and let the compiler figure out what variables to capture?.

[Jim Stichnoth, 2016/01/22 19:02:17]

Sweet, I had no idea!

+       getRegClassName](const ClFlags::StringVector &RegNames,
+                        std::vector<llvm::SmallBitVector> &RegSet) {
+        for (const IceString &RegClassAndName : RegNames) {
+          IceString RClass, RName;

[Karl, 2016/01/22 17:10:54]

I don't think our style allowed multiple variables in a declaration.

[Jim Stichnoth, 2016/01/22 19:02:17]

Not sure that style issue is actually addressed anywhere, but in any case I
separated it here, and also above (UseSet/ExcludeSet).

+          splitToClassAndName(RegClassAndName, &RClass, &RName);
+          if (!RegNameToIndex.count(RName)) {
+            BadRegNames.push_back(RName);
+            continue;
+          }
+          const int32_t RegIndex = RegNameToIndex.at(RName);
+          for (SizeT TypeIndex = 0; TypeIndex < TypeToRegisterSetSize;
+               ++TypeIndex) {
+            if (RClass.empty() ||
+                RClass == getRegClassName(static_cast<RegClass>(TypeIndex))) {
+              RegSet[TypeIndex][RegIndex] =
+                  TypeToRegisterSet[TypeIndex][RegIndex];
+            }
+          }
+        }
+      };
+
+  processRegList(Ctx->getFlags().getUseRestrictedRegisters(), UseSet);
+  processRegList(Ctx->getFlags().getExcludedRegisters(), ExcludeSet);
 
   if (!BadRegNames.empty()) {
     std::string Buffer;
     llvm::raw_string_ostream StrBuf(Buffer);
     StrBuf << "Unrecognized use/exclude registers:";
     for (const auto &RegName : BadRegNames)
       StrBuf << " " << RegName;
     llvm::report_fatal_error(StrBuf.str());
   }
 
   // Apply filters.
   for (size_t TypeIndex = 0; TypeIndex < TypeToRegisterSetSize; ++TypeIndex) {
     llvm::SmallBitVector *TypeBitSet = &TypeToRegisterSet[TypeIndex];
     llvm::SmallBitVector *UseBitSet = &UseSet[TypeIndex];
+    llvm::SmallBitVector *ExcludeBitSet = &ExcludeSet[TypeIndex];
     if (UseBitSet->any())
       *TypeBitSet = *UseBitSet;
-    *TypeBitSet &= ExcludeBitSet;
+    (*TypeBitSet).reset(*ExcludeBitSet);
   }
 
   // Display filtered register sets, if requested.
   if (BuildDefs::dump() && NumRegs &&
       (Ctx->getFlags().getVerbose() & IceV_AvailableRegs)) {
     Ostream &Str = Ctx->getStrDump();
     const IceString Indent = "  ";
     const IceString IndentTwice = Indent + Indent;
     Str << "Registers available for register allocation:\n";
     for (size_t TypeIndex = 0; TypeIndex < TypeToRegisterSetSize; ++TypeIndex) {
-      Str << Indent;
-      if (TypeIndex < IceType_NUM) {
-        Str << typeString(static_cast<Type>(TypeIndex));
-      } else {
-        Str << "other[" << TypeIndex << "]";
-      }
-      Str << ":\n";
+      Str << Indent << getRegClassName(static_cast<RegClass>(TypeIndex))
+          << ":\n";
       printRegisterSet(Str, TypeToRegisterSet[TypeIndex], getRegName,
                        IndentTwice);
     }
     Str << "\n";
   }
 }
 
 std::unique_ptr<TargetLowering>
 TargetLowering::createLowering(TargetArch Target, Cfg *Func) {
   switch (Target) {
@@ skipping 599 matching lines @@
   case Target_##X:                                                             \
     return ::X::createTargetHeaderLowering(Ctx);
 #include "llvm/Config/SZTargets.def"
 #undef SUBZERO_TARGET
   }
 }
 
 TargetHeaderLowering::~TargetHeaderLowering() = default;
 
 } // end of namespace Ice