Add a CoveredBySubRegs property to Register descriptions.

When set, this bit indicates that a register is completely defined by
the value of its sub-registers.

Use the CoveredBySubRegs property to infer which super-registers are
call-preserved given a list of callee-saved registers.  For example, the
ARM registers D8-D15 are callee-saved.  This now automatically implies
that Q4-Q7 are call-preserved.

Conversely, Win64 callees save XMM6-XMM15, but the corresponding
YMM6-YMM15 registers are not call-preserved because they are not fully
defined by their sub-registers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148363 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 41 insertions, 12 deletions

diff --git a/utils/TableGen/CodeGenRegisters.cpp b/utils/TableGen/CodeGenRegisters.cpp
index 89358c8d2f..7cd27a7d74 100644
--- a/utils/TableGen/CodeGenRegisters.cpp
+++ b/utils/TableGen/CodeGenRegisters.cpp
@@ -29,6 +29,7 @@ CodeGenRegister::CodeGenRegister(Record *R, unsigned Enum)
   : TheDef(R),
     EnumValue(Enum),
     CostPerUse(R->getValueAsInt("CostPerUse")),
+    CoveredBySubRegs(R->getValueAsBit("CoveredBySubRegs")),
     SubRegsComplete(false)
 {}
 
@@ -215,33 +216,40 @@ struct TupleExpander : SetTheory::Expander {
       for (unsigned i = 0, e = Proto->getValues().size(); i != e; ++i) {
         RecordVal RV = Proto->getValues()[i];
 
-        if (RV.getName() == "NAME")
+        // Skip existing fields, like NAME.
+        if (NewReg->getValue(RV.getNameInit()))
           continue;
 
+        StringRef Field = RV.getName();
+
         // Replace the sub-register list with Tuple.
-        if (RV.getName() == "SubRegs")
+        if (Field == "SubRegs")
           RV.setValue(ListInit::get(Tuple, RegisterRecTy));
 
         // Provide a blank AsmName. MC hacks are required anyway.
-        if (RV.getName() == "AsmName")
+        if (Field == "AsmName")
           RV.setValue(BlankName);
 
         // CostPerUse is aggregated from all Tuple members.
-        if (RV.getName() == "CostPerUse")
+        if (Field == "CostPerUse")
           RV.setValue(IntInit::get(CostPerUse));
 
+        // Composite registers are always covered by sub-registers.
+        if (Field == "CoveredBySubRegs")
+          RV.setValue(BitInit::get(true));
+
         // Copy fields from the RegisterTuples def.
-        if (RV.getName() == "SubRegIndices" ||
-            RV.getName() == "CompositeIndices") {
-          NewReg->addValue(*Def->getValue(RV.getName()));
+        if (Field == "SubRegIndices" ||
+            Field == "CompositeIndices") {
+          NewReg->addValue(*Def->getValue(Field));
           continue;
         }
 
         // Some fields get their default uninitialized value.
-        if (RV.getName() == "DwarfNumbers" ||
-            RV.getName() == "DwarfAlias" ||
-            RV.getName() == "Aliases") {
-          if (const RecordVal *DefRV = RegisterCl->getValue(RV.getName()))
+        if (Field == "DwarfNumbers" ||
+            Field == "DwarfAlias" ||
+            Field == "Aliases") {
+          if (const RecordVal *DefRV = RegisterCl->getValue(Field))
             NewReg->addValue(*DefRV);
           continue;
         }
@@ -1006,7 +1014,27 @@ BitVector CodeGenRegBank::computeCoveredRegisters(ArrayRef<Record*> Regs) {
   }
 
   // Second, find all super-registers that are completely covered by the set.
-  // FIXME: Implement CoveredBySubRegs bit.
+  for (unsigned i = 0; i != Set.size(); ++i) {
+    const CodeGenRegister::SuperRegList &SR = Set[i]->getSuperRegs();
+    for (unsigned j = 0, e = SR.size(); j != e; ++j) {
+      CodeGenRegister *Super = SR[j];
+      if (!Super->CoveredBySubRegs || Set.count(Super))
+        continue;
+      // This new super-register is covered by its sub-registers.
+      bool AllSubsInSet = true;
+      const CodeGenRegister::SubRegMap &SRM = Super->getSubRegs();
+      for (CodeGenRegister::SubRegMap::const_iterator I = SRM.begin(),
+             E = SRM.end(); I != E; ++I)
+        if (!Set.count(I->second)) {
+          AllSubsInSet = false;
+          break;
+        }
+      // All sub-registers in Set, add Super as well.
+      // We will visit Super later to recheck its super-registers.
+      if (AllSubsInSet)
+        Set.insert(Super);
+    }
+  }
 
   // Convert to BitVector.
   BitVector BV(Registers.size() + 1);
diff --git a/utils/TableGen/CodeGenRegisters.h b/utils/TableGen/CodeGenRegisters.h
index 6153fe5179..0551055806 100644
--- a/utils/TableGen/CodeGenRegisters.h
+++ b/utils/TableGen/CodeGenRegisters.h
@@ -36,6 +36,7 @@ namespace llvm {
     Record *TheDef;
     unsigned EnumValue;
     unsigned CostPerUse;
+    bool CoveredBySubRegs;
 
     // Map SubRegIndex -> Register.
     typedef std::map<Record*, CodeGenRegister*, LessRecord> SubRegMap;