Freeze the reserved registers as soon as isel is complete.

Also provide an MRI::getReservedRegs() function to access the frozen
register set, and isReserved() and isAllocatable() methods to test
individual registers.

The various implementations of TRI::getReservedRegs() are quite
complicated, and many passes need to look at the reserved register set.
This patch makes it possible for these passes to use the cached copy in
MRI, avoiding a lot of malloc traffic and repeated calculations.

llvm-svn: 165982

2 files changed, 10 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/MachineRegisterInfo.cpp b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
index 5fb938f3400..ae7c15be158 100644
--- a/llvm/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
@@ -306,22 +306,18 @@ void MachineRegisterInfo::dumpUses(unsigned Reg) const {
 
 void MachineRegisterInfo::freezeReservedRegs(const MachineFunction &MF) {
   ReservedRegs = TRI->getReservedRegs(MF);
+  assert(ReservedRegs.size() == TRI->getNumRegs() &&
+         "Invalid ReservedRegs vector from target");
 }
 
 bool MachineRegisterInfo::isConstantPhysReg(unsigned PhysReg,
                                             const MachineFunction &MF) const {
   assert(TargetRegisterInfo::isPhysicalRegister(PhysReg));
 
-  // Check if any overlapping register is modified.
+  // Check if any overlapping register is modified, or allocatable so it may be
+  // used later.
   for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI)
-    if (!def_empty(*AI))
-      return false;
-
-  // Check if any overlapping register is allocatable so it may be used later.
-  if (AllocatableRegs.empty())
-    AllocatableRegs = TRI->getAllocatableSet(MF);
-  for (MCRegAliasIterator AI(PhysReg, TRI, true); AI.isValid(); ++AI)
-    if (AllocatableRegs.test(*AI))
+    if (!def_empty(*AI) || isAllocatable(*AI))
       return false;
   return true;
 }
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 8fc9c70f995..c314fa5b511 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -474,6 +474,11 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
     MRI.replaceRegWith(From, To);
   }
 
+  // Freeze the set of reserved registers now that MachineFrameInfo has been
+  // set up. All the information required by getReservedRegs() should be
+  // available now.
+  MRI.freezeReservedRegs(*MF);
+
   // Release function-specific state. SDB and CurDAG are already cleared
   // at this point.
   FuncInfo->clear();