Add TRI::getSubClassWithSubReg(RC, Idx) function.

This function is used to constrain a register class to a sub-class that
supports the given sub-register index.

For example, getSubClassWithSubReg(GR32, sub_8bit) -> GR32_ABCD.

The function will be used to compute register classes when emitting
INSERT_SUBREG and EXTRACT_SUBREG nodes and for register class inflation
of sub-register operations.

The version provided by TableGen is usually adequate, but targets can
override.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141142 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 6 deletions

diff --git a/utils/TableGen/CodeGenRegisters.cpp b/utils/TableGen/CodeGenRegisters.cpp
index b731544616..8de4615279 100644
--- a/utils/TableGen/CodeGenRegisters.cpp
+++ b/utils/TableGen/CodeGenRegisters.cpp
@@ -768,23 +768,31 @@ void CodeGenRegBank::computeInferredRegisterClasses() {
     // Find matching classes for all SRSets entries.  Iterate in SubRegIndex
     // numerical order to visit synthetic indices last.
     for (unsigned sri = 0, sre = SubRegIndices.size(); sri != sre; ++sri) {
-      SubReg2SetMap::const_iterator I = SRSets.find(SubRegIndices[sri]);
+      Record *SubIdx = SubRegIndices[sri];
+      SubReg2SetMap::const_iterator I = SRSets.find(SubIdx);
       // Unsupported SubRegIndex. Skip it.
       if (I == SRSets.end())
         continue;
-      // In most cases, all RC registers support the SubRegIndex. Skip those.
-      if (I->second.size() == RC.getMembers().size())
+      // In most cases, all RC registers support the SubRegIndex.
+      if (I->second.size() == RC.getMembers().size()) {
+        RC.setSubClassWithSubReg(SubIdx, &RC);
         continue;
+      }
 
       // This is a real subset.  See if we have a matching class.
       CodeGenRegisterClass::Key K(&I->second, RC.SpillSize, RC.SpillAlignment);
       RCKeyMap::const_iterator FoundI = Key2RC.find(K);
-      if (FoundI != Key2RC.end())
+      if (FoundI != Key2RC.end()) {
+        RC.setSubClassWithSubReg(SubIdx, FoundI->second);
         continue;
+      }
 
       // Class doesn't exist.
-      addToMaps(new CodeGenRegisterClass(RC.getName() + "_with_" +
-                                         I->first->getName(), K));
+      CodeGenRegisterClass *NewRC =
+        new CodeGenRegisterClass(RC.getName() + "_with_" +
+                                 I->first->getName(), K);
+      addToMaps(NewRC);
+      RC.setSubClassWithSubReg(SubIdx, NewRC);
     }
   }
 }