This patch corrects logic in PPCFrameLowering for save and restore of

nonvolatile condition register fields across calls under the SVR4 ABIs.                                            
                                                                                                                   
 * With the 64-bit ABI, the save location is at a fixed offset of 8 from                                           
the stack pointer.  The frame pointer cannot be used to access this                                                
portion of the stack frame since the distance from the frame pointer may                                           
change with alloca calls.                                                                                          
                                                                                                                   
 * With the 32-bit ABI, the save location is just below the general
register save area, and is accessed via the frame pointer like the rest
of the save areas.  This is an optional slot, so it must only be created                                           
if any of CR2, CR3, and CR4 were modified.                                                                      
                                                                                                                   
 * For both ABIs, save/restore logic is generated only if one of the     
nonvolatile CR fields were modified.                                   

I also took this opportunity to clean up an extra FIXME in
PPCFrameLowering.h.  Save area offsets for 32-bit GPRs are meaningless
for the 64-bit ABI, so I removed them for correctness and efficiency.


Fixes PR13708 and partially also PR13623. It lets us enable exception handling
on PPC64.

Patch by William J. Schmidt!

llvm-svn: 163713

1 files changed, 31 insertions, 1 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
index ab8bf1f93a3..4d568c22f8e 100644
--- a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -71,7 +71,7 @@ PPCRegisterInfo::PPCRegisterInfo(const PPCSubtarget &ST,
   : PPCGenRegisterInfo(ST.isPPC64() ? PPC::LR8 : PPC::LR,
                        ST.isPPC64() ? 0 : 1,
                        ST.isPPC64() ? 0 : 1),
-    Subtarget(ST), TII(tii) {
+    Subtarget(ST), TII(tii), CRSpillFrameIdx(0) {
   ImmToIdxMap[PPC::LD]   = PPC::LDX;    ImmToIdxMap[PPC::STD]  = PPC::STDX;
   ImmToIdxMap[PPC::LBZ]  = PPC::LBZX;   ImmToIdxMap[PPC::STB]  = PPC::STBX;
   ImmToIdxMap[PPC::LHZ]  = PPC::LHZX;   ImmToIdxMap[PPC::LHA]  = PPC::LHAX;
@@ -111,6 +111,11 @@ PPCRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
     return Subtarget.isPPC64() ? CSR_Darwin64_SaveList :
                                  CSR_Darwin32_SaveList;
 
+  // For 32-bit SVR4, also initialize the frame index associated with
+  // the CR spill slot.
+  if (!Subtarget.isPPC64())
+    CRSpillFrameIdx = 0;
+
   return Subtarget.isPPC64() ? CSR_SVR464_SaveList : CSR_SVR432_SaveList;
 }
 
@@ -477,6 +482,31 @@ void PPCRegisterInfo::lowerCRRestore(MachineBasicBlock::iterator II,
   MBB.erase(II);
 }
 
+bool
+PPCRegisterInfo::hasReservedSpillSlot(const MachineFunction &MF,
+				      unsigned Reg, int &FrameIdx) const {
+
+  // For the nonvolatile condition registers (CR2, CR3, CR4) in an SVR4
+  // ABI, return true to prevent allocating an additional frame slot.
+  // For 64-bit, the CR save area is at SP+8; the value of FrameIdx = 0
+  // is arbitrary and will be subsequently ignored.  For 32-bit, we must
+  // create exactly one stack slot and return its FrameIdx for all
+  // nonvolatiles.
+  if (Subtarget.isSVR4ABI() && PPC::CR2 <= Reg && Reg <= PPC::CR4) {
+    if (Subtarget.isPPC64()) {
+      FrameIdx = 0;
+    } else if (CRSpillFrameIdx) {
+      FrameIdx = CRSpillFrameIdx;
+    } else {
+      MachineFrameInfo *MFI = ((MachineFunction &)MF).getFrameInfo();
+      FrameIdx = MFI->CreateFixedObject((uint64_t)4, (int64_t)-4, true);
+      CRSpillFrameIdx = FrameIdx;
+    }
+    return true;
+  }
+  return false;
+}
+
 void
 PPCRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
                                      int SPAdj, RegScavenger *RS) const {