AArch64: Replace a RegScavenger instance with LivePhysRegs

findScratchNonCalleeSaveRegister() just needs a simple liveness
analysis, use LivePhysRegs for that as it is simpler and does not depend
on the kill flags.

This commit adds a convenience function available() to LivePhysRegs:
This function returns true if the given register is not reserved and
neither the register nor any of its aliases are alive.

Differential Revision: http://reviews.llvm.org/D21865

llvm-svn: 274685

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LivePhysRegs.cpp b/llvm/lib/CodeGen/LivePhysRegs.cpp
index eb2955045fd..57faef3c297 100644
--- a/llvm/lib/CodeGen/LivePhysRegs.cpp
+++ b/llvm/lib/CodeGen/LivePhysRegs.cpp
@@ -17,6 +17,7 @@
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBundle.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
@@ -126,6 +127,19 @@ LLVM_DUMP_METHOD void LivePhysRegs::dump() const {
 #endif
 }
 
+bool LivePhysRegs::available(const MachineRegisterInfo &MRI,
+                             unsigned Reg) const {
+  if (LiveRegs.count(Reg))
+    return false;
+  if (MRI.isReserved(Reg))
+    return false;
+  for (MCRegAliasIterator R(Reg, TRI, false); R.isValid(); ++R) {
+    if (LiveRegs.count(*R))
+      return false;
+  }
+  return true;
+}
+
 /// Add live-in registers of basic block \p MBB to \p LiveRegs.
 static void addLiveIns(LivePhysRegs &LiveRegs, const MachineBasicBlock &MBB) {
   for (const auto &LI : MBB.liveins())