Change MRegisterDesc::AliasSet, TargetInstrDescriptor::ImplicitDefs

and TargetInstrDescriptor::ImplicitUses to always point to a null
terminated array and never be null. So there is no need to check for
pointer validity when iterating over those sets. Code that looked
like:

if (const unsigned* AS = TID.ImplicitDefs) {
  for (int i = 0; AS[i]; ++i) {
    // use AS[i]
  }
}

was changed to:

for (const unsigned* AS = TID.ImplicitDefs; *AS; ++AS) {
  // use *AS
}


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8960 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 64 insertions, 48 deletions

diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index d38ed274e3..2a9b70d3b0 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -108,12 +108,14 @@ void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
   if (PhysRegInfo[Reg]) {
     PhysRegInfo[Reg] = MI;
     PhysRegUsed[Reg] = true;
-  } else if (const unsigned *AliasSet = RegInfo->getAliasSet(Reg)) {
-    for (; unsigned NReg = AliasSet[0]; ++AliasSet)
-      if (MachineInstr *LastUse = PhysRegInfo[NReg]) {
-	PhysRegInfo[NReg] = MI;
-	PhysRegUsed[NReg] = true;
+  } else {
+    for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+         *AliasSet; ++AliasSet) {
+      if (MachineInstr *LastUse = PhysRegInfo[*AliasSet]) {
+	PhysRegInfo[*AliasSet] = MI;
+	PhysRegUsed[*AliasSet] = true;
       }
+    }
   }
 }
 
@@ -124,15 +126,17 @@ void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
       RegistersKilled.insert(std::make_pair(LastUse, Reg));
     else
       RegistersDead.insert(std::make_pair(LastUse, Reg));
-  } else if (const unsigned *AliasSet = RegInfo->getAliasSet(Reg)) {
-    for (; unsigned NReg = AliasSet[0]; ++AliasSet)
-      if (MachineInstr *LastUse = PhysRegInfo[NReg]) {
-	if (PhysRegUsed[NReg])
-	  RegistersKilled.insert(std::make_pair(LastUse, NReg));
+  } else {
+    for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+         *AliasSet; ++AliasSet) {
+      if (MachineInstr *LastUse = PhysRegInfo[*AliasSet]) {
+	if (PhysRegUsed[*AliasSet])
+	  RegistersKilled.insert(std::make_pair(LastUse, *AliasSet));
 	else
-	  RegistersDead.insert(std::make_pair(LastUse, NReg));
-	PhysRegInfo[NReg] = 0;  // Kill the aliased register
+	  RegistersDead.insert(std::make_pair(LastUse, *AliasSet));
+	PhysRegInfo[*AliasSet] = 0;  // Kill the aliased register
       }
+    }
   }
   PhysRegInfo[Reg] = MI;
   PhysRegUsed[Reg] = false;
@@ -206,9 +210,9 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &MF) {
 	NumOperandsToProcess = 1;
 
       // Loop over implicit uses, using them.
-      if (const unsigned *ImplicitUses = MID.ImplicitUses)
-	for (unsigned i = 0; ImplicitUses[i]; ++i)
-	  HandlePhysRegUse(ImplicitUses[i], MI);
+      for (const unsigned *ImplicitUses = MID.ImplicitUses;
+           *ImplicitUses; ++ImplicitUses)
+	HandlePhysRegUse(*ImplicitUses, MI);
 
       // Process all explicit uses...
       for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp
index 13cd353362..0ceb866965 100644
--- a/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/lib/CodeGen/PrologEpilogInserter.cpp
@@ -127,12 +127,15 @@ void PEI::saveCallerSavedRegisters(MachineFunction &Fn) {
     unsigned Reg = CSRegs[i];
     if (ModifiedRegs[Reg]) {
       RegsToSave.push_back(Reg);  // If modified register...
-    } else if (const unsigned *AliasSet = RegInfo->getAliasSet(Reg))
-      for (unsigned j = 0; AliasSet[j]; ++j)     // Check alias registers too...
-	if (ModifiedRegs[AliasSet[j]]) {
+    } else {
+      for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+           *AliasSet; ++AliasSet) {  // Check alias registers too...
+	if (ModifiedRegs[*AliasSet]) {
 	  RegsToSave.push_back(Reg);
 	  break;
 	}
+      }
+    }
   }
 
   if (RegsToSave.empty())
diff --git a/lib/CodeGen/RegAllocLocal.cpp b/lib/CodeGen/RegAllocLocal.cpp
index 331a291753..6b71e288e7 100644
--- a/lib/CodeGen/RegAllocLocal.cpp
+++ b/lib/CodeGen/RegAllocLocal.cpp
@@ -120,9 +120,10 @@ namespace {
     ///
     bool areRegsEqual(unsigned R1, unsigned R2) const {
       if (R1 == R2) return true;
-      if (const unsigned *AliasSet = RegInfo->getAliasSet(R2))
-        for (unsigned i = 0; AliasSet[i]; ++i)
-          if (AliasSet[i] == R1) return true;
+      for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
+           *AliasSet; ++AliasSet) {
+        if (*AliasSet == R1) return true;
+      }
       return false;
     }
 
@@ -271,14 +272,15 @@ void RA::spillPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
   if (PI != PhysRegsUsed.end()) {             // Only spill it if it's used!
     if (PI->second || !OnlyVirtRegs)
       spillVirtReg(MBB, I, PI->second, PhysReg);
-  } else if (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg)) {
+  } else {
     // If the selected register aliases any other registers, we must make
     // sure that one of the aliases isn't alive...
-    for (unsigned i = 0; AliasSet[i]; ++i) {
-      PI = PhysRegsUsed.find(AliasSet[i]);
+    for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
+         *AliasSet; ++AliasSet) {
+      PI = PhysRegsUsed.find(*AliasSet);
       if (PI != PhysRegsUsed.end())     // Spill aliased register...
         if (PI->second || !OnlyVirtRegs)
-          spillVirtReg(MBB, I, PI->second, AliasSet[i]);
+          spillVirtReg(MBB, I, PI->second, *AliasSet);
     }
   }
 }
@@ -308,10 +310,10 @@ bool RA::isPhysRegAvailable(unsigned PhysReg) const {
 
   // If the selected register aliases any other allocated registers, it is
   // not free!
-  if (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg))
-    for (unsigned i = 0; AliasSet[i]; ++i)
-      if (PhysRegsUsed.count(AliasSet[i])) // Aliased register in use?
-        return false;                      // Can't use this reg then.
+  for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
+       *AliasSet; ++AliasSet)
+    if (PhysRegsUsed.count(*AliasSet)) // Aliased register in use?
+      return false;                    // Can't use this reg then.
   return true;
 }
 
@@ -414,12 +416,13 @@ unsigned RA::getReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
         } else {
           // If one of the registers aliased to the current register is
           // compatible, use it.
-          if (const unsigned *AliasSet = RegInfo->getAliasSet(R))
-            for (unsigned a = 0; AliasSet[a]; ++a)
-              if (RegInfo->getRegClass(AliasSet[a]) == RC) {
-                PhysReg = AliasSet[a];    // Take an aliased register
-                break;
-              }
+          for (const unsigned *AliasSet = RegInfo->getAliasSet(R);
+               *AliasSet; ++AliasSet) {
+            if (RegInfo->getRegClass(*AliasSet) == RC) {
+              PhysReg = *AliasSet;    // Take an aliased register
+              break;
+            }
+          }
         }
       }
     }
@@ -485,9 +488,9 @@ void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
 
     // Loop over the implicit uses, making sure that they are at the head of the
     // use order list, so they don't get reallocated.
-    if (const unsigned *ImplicitUses = TID.ImplicitUses)
-      for (unsigned i = 0; ImplicitUses[i]; ++i)
-        MarkPhysRegRecentlyUsed(ImplicitUses[i]);
+    for (const unsigned *ImplicitUses = TID.ImplicitUses;
+         *ImplicitUses; ++ImplicitUses)
+        MarkPhysRegRecentlyUsed(*ImplicitUses);
 
     // Get the used operands into registers.  This has the potential to spill
     // incoming values if we are out of registers.  Note that we completely
diff --git a/lib/CodeGen/RegAllocSimple.cpp b/lib/CodeGen/RegAllocSimple.cpp
index 57d678b02f..dbf731ecc7 100644
--- a/lib/CodeGen/RegAllocSimple.cpp
+++ b/lib/CodeGen/RegAllocSimple.cpp
@@ -153,13 +153,13 @@ void RegAllocSimple::AllocateBasicBlock(MachineBasicBlock &MBB) {
     // are used by the instruction (including implicit uses)
     unsigned Opcode = MI->getOpcode();
     const TargetInstrDescriptor &Desc = TM->getInstrInfo().get(Opcode);
-    if (const unsigned *Regs = Desc.ImplicitUses)
-      while (*Regs)
-	RegsUsed[*Regs++] = true;
+    const unsigned *Regs = Desc.ImplicitUses;
+    while (*Regs)
+      RegsUsed[*Regs++] = true;
     
-    if (const unsigned *Regs = Desc.ImplicitDefs)
-      while (*Regs)
-	RegsUsed[*Regs++] = true;
+    Regs = Desc.ImplicitDefs;
+    while (*Regs)
+      RegsUsed[*Regs++] = true;
     
     // Loop over uses, move from memory into registers
     for (int i = MI->getNumOperands() - 1; i >= 0; --i) {
diff --git a/utils/TableGen/InstrInfoEmitter.cpp b/utils/TableGen/InstrInfoEmitter.cpp
index c794cd0441..7b64f922f6 100644
--- a/utils/TableGen/InstrInfoEmitter.cpp
+++ b/utils/TableGen/InstrInfoEmitter.cpp
@@ -65,6 +65,10 @@ void InstrInfoEmitter::run(std::ostream &OS) {
   std::vector<Record*> Instructions =
     Records.getAllDerivedDefinitions("Instruction");
   
+  // Emit empty implicit uses and defs lists
+  OS << "static const unsigned EmptyImpUses[] = { 0 };\n"
+     << "static const unsigned EmptyImpDefs[] = { 0 };\n";
+
   // Emit all of the instruction's implicit uses and defs...
   for (unsigned i = 0, e = Instructions.size(); i != e; ++i) {
     Record *Inst = Instructions[i];
@@ -113,13 +117,13 @@ void InstrInfoEmitter::emitRecord(Record *R, unsigned Num, Record *InstrInfo,
   // Emit the implicit uses and defs lists...
   LI = R->getValueAsListInit("Uses");
   if (!LI->getSize())
-    OS << "0, ";
+    OS << "EmptyImpUses, ";
   else 
     OS << R->getName() << "ImpUses, ";
 
   LI = R->getValueAsListInit("Defs");
   if (!LI->getSize())
-    OS << "0 ";
+    OS << "EmptyImpDefs ";
   else 
     OS << R->getName() << "ImpDefs ";
 
diff --git a/utils/TableGen/RegisterInfoEmitter.cpp b/utils/TableGen/RegisterInfoEmitter.cpp
index af3efe3a9c..7652e67772 100644
--- a/utils/TableGen/RegisterInfoEmitter.cpp
+++ b/utils/TableGen/RegisterInfoEmitter.cpp
@@ -138,7 +138,7 @@ void RegisterInfoEmitter::run(std::ostream &OS) {
   std::vector<Record*> RegisterAliasesRecs =
     Records.getAllDerivedDefinitions("RegisterAliases");
   std::map<Record*, std::set<Record*> > RegisterAliases;
-  
+
   for (unsigned i = 0, e = RegisterAliasesRecs.size(); i != e; ++i) {
     Record *AS = RegisterAliasesRecs[i];
     Record *R = AS->getValueAsDef("Reg");
@@ -166,6 +166,8 @@ void RegisterInfoEmitter::run(std::ostream &OS) {
   if (!RegisterAliases.empty())
     OS << "\n\n  // Register Alias Sets...\n";
   
+  // Emit the empty alias list
+  OS << "  const unsigned Empty_AliasSet[] = { 0 };\n";
   // Loop over all of the registers which have aliases, emitting the alias list
   // to memory.
   for (std::map<Record*, std::set<Record*> >::iterator
@@ -192,7 +194,7 @@ void RegisterInfoEmitter::run(std::ostream &OS) {
     if (RegisterAliases.count(Reg))
       OS << Reg->getName() << "_AliasSet,\t";
     else
-      OS << "0,\t\t";
+      OS << "Empty_AliasSet,\t";
     OS << "0, 0 },\n";    
   }
   OS << "  };\n";      // End of register descriptors...