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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165982 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 9 deletions

diff --git a/lib/CodeGen/MachineRegisterInfo.cpp b/lib/CodeGen/MachineRegisterInfo.cpp
index 5fb938f340..ae7c15be15 100644
--- a/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/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;
 }