Change StackDirection from StackGrowsUp to StackGrowsDown.

The following improvements are accomplished as a result of applying this patch:
- Fixed frame objects' offsets (relative to either the virtual frame pointer or
  the stack pointer) are set before instruction selection is completed. There is
  no need to wait until Prologue/Epilogue Insertion is run to set them.
- Calculation of final offsets of fixed frame objects is straightforward. It is
  no longer necessary to assign negative offsets to fixed objects for incoming
  arguments in order to distinguish them from the others.
- Since a fixed object has its relative offset set during instruction
  selection, there is no need to conservatively set its alignment to 4.
- It is no longer necessary to reorder non-fixed frame objects in 
  MipsFrameLowering::adjustMipsStackFrame.

llvm-svn: 131915

1 files changed, 23 insertions, 22 deletions

diff --git a/llvm/lib/Target/Mips/MipsRegisterInfo.cpp b/llvm/lib/Target/Mips/MipsRegisterInfo.cpp
index a9b5750c234..00e2063798b 100644
--- a/llvm/lib/Target/Mips/MipsRegisterInfo.cpp
+++ b/llvm/lib/Target/Mips/MipsRegisterInfo.cpp
@@ -98,22 +98,22 @@ getCalleeSavedRegs(const MachineFunction *MF) const
 {
   // Mips callee-save register range is $16-$23, $f20-$f30
   static const unsigned SingleFloatOnlyCalleeSavedRegs[] = {
-    Mips::S0, Mips::S1, Mips::S2, Mips::S3,
-    Mips::S4, Mips::S5, Mips::S6, Mips::S7, Mips::FP, Mips::RA,
-    Mips::F20, Mips::F21, Mips::F22, Mips::F23, Mips::F24, Mips::F25,
-    Mips::F26, Mips::F27, Mips::F28, Mips::F29, Mips::F30, 0
+    Mips::F30, Mips::F29, Mips::F28, Mips::F27, Mips::F26,
+    Mips::F25, Mips::F24, Mips::F23, Mips::F22, Mips::F21, Mips::F20,
+    Mips::RA, Mips::FP, Mips::S7, Mips::S6, Mips::S5, Mips::S4,
+    Mips::S3, Mips::S2, Mips::S1, Mips::S0, 0
   };
 
   static const unsigned BitMode32CalleeSavedRegs[] = {
-    Mips::S0, Mips::S1, Mips::S2, Mips::S3,
-    Mips::S4, Mips::S5, Mips::S6, Mips::S7, Mips::FP, Mips::RA,
-    Mips::F20, Mips::F22, Mips::F24, Mips::F26, Mips::F28, Mips::F30, 0
+    Mips::F30, Mips::F28, Mips::F26, Mips::F24, Mips::F22, Mips::F20,
+    Mips::RA, Mips::FP, Mips::S7, Mips::S6, Mips::S5, Mips::S4,
+    Mips::S3, Mips::S2, Mips::S1, Mips::S0, 0
   };
 
   static const unsigned Mips32CalleeSavedRegs[] = {
-    Mips::S0, Mips::S1, Mips::S2, Mips::S3,
-    Mips::S4, Mips::S5, Mips::S6, Mips::S7, Mips::FP, Mips::RA,
-    Mips::D10, Mips::D11, Mips::D12, Mips::D13, Mips::D14, Mips::D15, 0
+    Mips::D15, Mips::D14, Mips::D13, Mips::D12, Mips::D11, Mips::D10,
+    Mips::RA, Mips::FP, Mips::S7, Mips::S6, Mips::S5, Mips::S4,
+    Mips::S3, Mips::S2, Mips::S1, Mips::S0, 0
   };
 
   if (Subtarget.isSingleFloat())
@@ -182,9 +182,19 @@ eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj,
                << "spOffset   : " << spOffset << "\n"
                << "stackSize  : " << stackSize << "\n");
 
-  // as explained on LowerFormalArguments, detect negative offsets
-  // and adjust SPOffsets considering the final stack size.
-  int Offset = ((spOffset < 0) ? (stackSize + (-(spOffset+4))) : (spOffset));
+  int Offset;
+
+  // Calculate final offset.
+  // - There is no need to change the offset if the frame object is an outgoing
+  //   argument or a $gp restore location,
+  // - 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.  
+  if (MipsFI->isOutArgFI(FrameIndex) || MipsFI->isGPFI(FrameIndex))
+    Offset = spOffset;
+  else
+    Offset = spOffset + stackSize;
+
   Offset    += MI.getOperand(i-1).getImm();
 
   DEBUG(errs() << "Offset     : " << Offset << "\n" << "<--------->\n");
@@ -247,15 +257,6 @@ eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj,
   MI.getOperand(i-1).ChangeToImmediate(NewImm);
 }
 
-void MipsRegisterInfo::
-processFunctionBeforeFrameFinalized(MachineFunction &MF) const {
-  // Set the stack offset where GP must be saved/loaded from.
-  MachineFrameInfo *MFI = MF.getFrameInfo();
-  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
-  if (MipsFI->needGPSaveRestore())
-    MFI->setObjectOffset(MipsFI->getGPFI(), MipsFI->getGPStackOffset());
-}
-
 unsigned MipsRegisterInfo::
 getRARegister() const {
   return Mips::RA;