From ad26f4ded2a07fe9b25daca5a09c2d9b0c17a6c5 Mon Sep 17 00:00:00 2001
From: Hal Finkel <hfinkel@anl.gov>
Date: Thu, 14 Mar 2013 20:21:47 +0000
Subject: [PATCH] Use frame-index scavenging for PPC register spilling

Make requiresFrameIndexScavenging return true, and create virtual registers in
the spilling code instead of using the register scavenger directly. This makes
the target-level code simpler, and importantly, delays the scavenging until
after callee-saved register processing (which will be important for later
changes).

Also cleans up trackLivenessAfterRegAlloc (makes it inline in the header with
the other related functions). This makes it clear that it always returns true.

No functionality change intended.

llvm-svn: 177107
---
 llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp | 26 ++------------------------
 llvm/lib/Target/PowerPC/PPCRegisterInfo.h   | 10 ++++++++--
 2 files changed, 10 insertions(+), 26 deletions(-)

diff --git a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
index 3e5ee75..cf397a5 100644
--- a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -71,12 +71,6 @@ PPCRegisterInfo::PPCRegisterInfo(const PPCSubtarget &ST,
   ImmToIdxMap[PPC::ADDI8] = PPC::ADD8; ImmToIdxMap[PPC::STD_32] = PPC::STDX_32;
 }
 
-bool
-PPCRegisterInfo::trackLivenessAfterRegAlloc(const MachineFunction &MF) const {
-  return requiresRegisterScavenging(MF);
-}
-
-
 /// getPointerRegClass - Return the register class to use to hold pointers.
 /// This is used for addressing modes.
 const TargetRegisterClass *
@@ -187,20 +181,6 @@ PPCRegisterInfo::avoidWriteAfterWrite(const TargetRegisterClass *RC) const {
 // Stack Frame Processing methods
 //===----------------------------------------------------------------------===//
 
-/// findScratchRegister - Find a 'free' PPC register. Try for a call-clobbered
-/// register first and then a spilled callee-saved register if that fails.
-static
-unsigned findScratchRegister(MachineBasicBlock::iterator II, RegScavenger *RS,
-                             const TargetRegisterClass *RC, int SPAdj) {
-  assert(RS && "Register scavenging must be on");
-  unsigned Reg = RS->FindUnusedReg(RC);
-  // FIXME: move ARM callee-saved reg scan to target independent code, then 
-  // search for already spilled CS register here.
-  if (Reg == 0)
-    Reg = RS->scavengeRegister(RC, II, SPAdj);
-  return Reg;
-}
-
 /// lowerDynamicAlloc - Generate the code for allocating an object in the
 /// current frame.  The sequence of code with be in the general form
 ///
@@ -241,9 +221,7 @@ void PPCRegisterInfo::lowerDynamicAlloc(MachineBasicBlock::iterator II,
   // Fortunately, a frame greater than 32K is rare.
   const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
   const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
-  const TargetRegisterClass *RC = LP64 ? G8RC : GPRC;
-
-  unsigned Reg = findScratchRegister(II, RS, RC, SPAdj);
+  unsigned Reg = MF.getRegInfo().createVirtualRegister(LP64 ? G8RC : GPRC);
   
   if (MaxAlign < TargetAlign && isInt<16>(FrameSize)) {
     BuildMI(MBB, II, dl, TII.get(PPC::ADDI), Reg)
@@ -514,7 +492,7 @@ PPCRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
 
   const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
   const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
-  unsigned SReg = findScratchRegister(II, RS, is64Bit ? G8RC : GPRC, SPAdj);
+  unsigned SReg = MF.getRegInfo().createVirtualRegister(is64Bit ? G8RC : GPRC);
 
   // Insert a set of rA with the full offset value before the ld, st, or add
   BuildMI(MBB, II, dl, TII.get(is64Bit ? PPC::LIS8 : PPC::LIS), SReg)
diff --git a/llvm/lib/Target/PowerPC/PPCRegisterInfo.h b/llvm/lib/Target/PowerPC/PPCRegisterInfo.h
index 83f755d..1be3fbc 100644
--- a/llvm/lib/Target/PowerPC/PPCRegisterInfo.h
+++ b/llvm/lib/Target/PowerPC/PPCRegisterInfo.h
@@ -49,12 +49,18 @@ public:
 
   virtual bool avoidWriteAfterWrite(const TargetRegisterClass *RC) const;
 
-  /// requiresRegisterScavenging - We require a register scavenger.
+  /// We require the register scavenger.
   bool requiresRegisterScavenging(const MachineFunction &MF) const {
     return true;
   }
 
-  bool trackLivenessAfterRegAlloc(const MachineFunction &MF) const;
+  bool requiresFrameIndexScavenging(const MachineFunction &MF) const {
+    return true;
+  }
+
+  bool trackLivenessAfterRegAlloc(const MachineFunction &MF) const {
+    return true;
+  }
 
   void lowerDynamicAlloc(MachineBasicBlock::iterator II,
                          int SPAdj, RegScavenger *RS) const;
-- 
2.7.4