TableGen: Produce CoveredBySubRegs summary for register classes

This will be used in the upcoming "DetectDeadLanes" pass.

llvm-svn: 267850

4 files changed, 12 insertions, 3 deletions

diff --git a/llvm/include/llvm/Target/TargetRegisterInfo.h b/llvm/include/llvm/Target/TargetRegisterInfo.h
index 7eb506c2269..77705449a2f 100644
--- a/llvm/include/llvm/Target/TargetRegisterInfo.h
+++ b/llvm/include/llvm/Target/TargetRegisterInfo.h
@@ -70,6 +70,9 @@ public:
   const uint8_t AllocationPriority;
   /// Whether the class supports two (or more) disjunct subregister indices.
   const bool HasDisjunctSubRegs;
+  /// Whether a combination of subregisters can cover every register in the
+  /// class. See also the CoveredBySubRegs description in Target.td.
+  const bool CoveredBySubRegs;
   const sc_iterator SuperClasses;
   ArrayRef<MCPhysReg> (*OrderFunc)(const MachineFunction&);
 
diff --git a/llvm/utils/TableGen/CodeGenRegisters.cpp b/llvm/utils/TableGen/CodeGenRegisters.cpp
index 114ee18a5f3..626144fbe85 100644
--- a/llvm/utils/TableGen/CodeGenRegisters.cpp
+++ b/llvm/utils/TableGen/CodeGenRegisters.cpp
@@ -1829,11 +1829,14 @@ void CodeGenRegBank::computeDerivedInfo() {
 
   computeRegUnitLaneMasks();
 
-  // Compute register class HasDisjunctSubRegs flag.
+  // Compute register class HasDisjunctSubRegs/CoveredBySubRegs flag.
   for (CodeGenRegisterClass &RC : RegClasses) {
     RC.HasDisjunctSubRegs = false;
-    for (const CodeGenRegister *Reg : RC.getMembers())
+    RC.CoveredBySubRegs = true;
+    for (const CodeGenRegister *Reg : RC.getMembers()) {
       RC.HasDisjunctSubRegs |= Reg->HasDisjunctSubRegs;
+      RC.CoveredBySubRegs &= Reg->CoveredBySubRegs;
+    }
   }
 
   // Get the weight of each set.
diff --git a/llvm/utils/TableGen/CodeGenRegisters.h b/llvm/utils/TableGen/CodeGenRegisters.h
index 83b5996b45b..b8d47aa4ff8 100644
--- a/llvm/utils/TableGen/CodeGenRegisters.h
+++ b/llvm/utils/TableGen/CodeGenRegisters.h
@@ -310,6 +310,7 @@ namespace llvm {
     unsigned LaneMask;
     /// True if there are at least 2 subregisters which do not interfere.
     bool HasDisjunctSubRegs;
+    bool CoveredBySubRegs;
 
     // Return the Record that defined this class, or NULL if the class was
     // created by TableGen.
diff --git a/llvm/utils/TableGen/RegisterInfoEmitter.cpp b/llvm/utils/TableGen/RegisterInfoEmitter.cpp
index 4ec3e7de0f7..3316da6185c 100644
--- a/llvm/utils/TableGen/RegisterInfoEmitter.cpp
+++ b/llvm/utils/TableGen/RegisterInfoEmitter.cpp
@@ -1311,7 +1311,9 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
          << format("0x%08x,\n    ", RC.LaneMask)
          << (unsigned)RC.AllocationPriority << ",\n    "
          << (RC.HasDisjunctSubRegs?"true":"false")
-         << ", /* HasDisjunctSubRegs */\n    ";
+         << ", /* HasDisjunctSubRegs */\n    "
+         << (RC.CoveredBySubRegs?"true":"false")
+         << ", /* CoveredBySubRegs */\n    ";
       if (RC.getSuperClasses().empty())
         OS << "NullRegClasses,\n    ";
       else