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
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index 48d4e11..5fbec7e4 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -93,6 +93,7 @@
#include "AArch64Subtarget.h"
#include "AArch64TargetMachine.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -244,27 +245,26 @@
if (&MF->front() == MBB)
return AArch64::X9;
- RegScavenger RS;
- RS.enterBasicBlock(*MBB);
+ const TargetRegisterInfo &TRI = *MF->getSubtarget().getRegisterInfo();
+ LivePhysRegs LiveRegs(&TRI);
+ LiveRegs.addLiveIns(*MBB);
- // Prefer X9 since it was historically used for the prologue scratch reg.
- if (!RS.isRegUsed(AArch64::X9))
- return AArch64::X9;
-
- // Find a free non callee-save reg.
+ // Mark callee saved registers as used so we will not choose them.
const AArch64Subtarget &Subtarget = MF->getSubtarget<AArch64Subtarget>();
const AArch64RegisterInfo *RegInfo = Subtarget.getRegisterInfo();
const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(MF);
- BitVector CalleeSaveRegs(RegInfo->getNumRegs());
for (unsigned i = 0; CSRegs[i]; ++i)
- CalleeSaveRegs.set(CSRegs[i]);
+ LiveRegs.addReg(CSRegs[i]);
- BitVector Available = RS.getRegsAvailable(&AArch64::GPR64RegClass);
- for (int AvailReg = Available.find_first(); AvailReg != -1;
- AvailReg = Available.find_next(AvailReg))
- if (!CalleeSaveRegs.test(AvailReg))
- return AvailReg;
+ // Prefer X9 since it was historically used for the prologue scratch reg.
+ const MachineRegisterInfo &MRI = MF->getRegInfo();
+ if (LiveRegs.available(MRI, AArch64::X9))
+ return AArch64::X9;
+ for (unsigned Reg : AArch64::GPR64RegClass) {
+ if (LiveRegs.available(MRI, Reg))
+ return Reg;
+ }
return AArch64::NoRegister;
}