Simplify RegScavenger::FindUnusedReg.

- Drop the Candidates argument and fix all callers. Now that RegScavenger
  tracks available registers accurately, there is no need to restict the
  search.
- Make sure that no aliases of the found register are in use. This was a potential bug.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79369 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 3 insertions, 11 deletions

diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index 09ab87c..07164ff 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -1006,12 +1006,8 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
 static
 unsigned findScratchRegister(RegScavenger *RS, const TargetRegisterClass *RC,
                              ARMFunctionInfo *AFI) {
-  unsigned Reg = RS ? RS->FindUnusedReg(RC, true) : (unsigned) ARM::R12;
+  unsigned Reg = RS ? RS->FindUnusedReg(RC) : (unsigned) ARM::R12;
   assert(!AFI->isThumb1OnlyFunction());
-  if (Reg == 0)
-    // Try a already spilled CS register.
-    Reg = RS->FindUnusedReg(RC, AFI->getSpilledCSRegisters());
-
   return Reg;
 }
 
diff --git a/lib/Target/ARM/ARMLoadStoreOptimizer.cpp b/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
index 3c6778f..d927dd2 100644
--- a/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
+++ b/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
@@ -941,12 +941,8 @@ bool ARMLoadStoreOpt::LoadStoreMultipleOpti(MachineBasicBlock &MBB) {
         // Try to find a free register to use as a new base in case it's needed.
         // First advance to the instruction just before the start of the chain.
         AdvanceRS(MBB, MemOps);
-        // Find a scratch register. Make sure it's a call clobbered register or
-        // a spilled callee-saved register.
-        unsigned Scratch = RS->FindUnusedReg(&ARM::GPRRegClass, true);
-        if (!Scratch)
-          Scratch = RS->FindUnusedReg(&ARM::GPRRegClass,
-                                      AFI->getSpilledCSRegisters());
+        // Find a scratch register.
+        unsigned Scratch = RS->FindUnusedReg(&ARM::GPRRegClass);
         // Process the load / store instructions.
         RS->forward(prior(MBBI));