[mips] Stop reserving register AT and use register scavenger when a scratch

register is needed.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167341 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 4 deletions

diff --git a/lib/Target/Mips/MipsSERegisterInfo.cpp b/lib/Target/Mips/MipsSERegisterInfo.cpp
index b35d05c563..56b9ba95e5 100644
--- a/lib/Target/Mips/MipsSERegisterInfo.cpp
+++ b/lib/Target/Mips/MipsSERegisterInfo.cpp
@@ -26,6 +26,7 @@
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Target/TargetFrameLowering.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
@@ -43,6 +44,16 @@ MipsSERegisterInfo::MipsSERegisterInfo(const MipsSubtarget &ST,
                                        const MipsSEInstrInfo &I)
   : MipsRegisterInfo(ST), TII(I) {}
 
+bool MipsSERegisterInfo::
+requiresRegisterScavenging(const MachineFunction &MF) const {
+  return true;
+}
+
+bool MipsSERegisterInfo::
+requiresFrameIndexScavenging(const MachineFunction &MF) const {
+  return true;
+}
+
 // This function eliminate ADJCALLSTACKDOWN,
 // ADJCALLSTACKUP pseudo instructions
 void MipsSERegisterInfo::
@@ -102,6 +113,7 @@ void MipsSERegisterInfo::eliminateFI(MachineBasicBlock::iterator II,
   // - If the frame object is any of the following, its offset must be adjusted
   //   by adding the size of the stack:
   //   incoming argument, callee-saved register location or local variable.
+  bool IsKill = false;
   int64_t Offset;
 
   Offset = SPOffset + (int64_t)StackSize;
@@ -115,16 +127,17 @@ void MipsSERegisterInfo::eliminateFI(MachineBasicBlock::iterator II,
     MachineBasicBlock &MBB = *MI.getParent();
     DebugLoc DL = II->getDebugLoc();
     unsigned ADDu = Subtarget.isABI_N64() ? Mips::DADDu : Mips::ADDu;
-    unsigned ATReg = Subtarget.isABI_N64() ? Mips::AT_64 : Mips::AT;
     unsigned NewImm;
 
     unsigned Reg = TII.loadImmediate(Offset, MBB, II, DL, &NewImm);
-    BuildMI(MBB, II, DL, TII.get(ADDu), ATReg).addReg(FrameReg).addReg(Reg);
+    BuildMI(MBB, II, DL, TII.get(ADDu), Reg).addReg(FrameReg)
+      .addReg(Reg, RegState::Kill);
 
-    FrameReg = ATReg;
+    FrameReg = Reg;
     Offset = SignExtend64<16>(NewImm);
+    IsKill = true;
   }
 
-  MI.getOperand(OpNo).ChangeToRegister(FrameReg, false);
+  MI.getOperand(OpNo).ChangeToRegister(FrameReg, false, false, IsKill);
   MI.getOperand(OpNo + 1).ChangeToImmediate(Offset);
 }