[mips] Add function MipsFrameLowering::estimateStackSize.

This function estimates stack size and will be called before
PrologEpilogInserter scans the callee-saved registers.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167313 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 34 insertions, 0 deletions

diff --git a/lib/Target/Mips/MipsFrameLowering.cpp b/lib/Target/Mips/MipsFrameLowering.cpp
index 6dd251c054..2cad2a6264 100644
--- a/lib/Target/Mips/MipsFrameLowering.cpp
+++ b/lib/Target/Mips/MipsFrameLowering.cpp
@@ -98,3 +98,37 @@ bool MipsFrameLowering::hasFP(const MachineFunction &MF) const {
   return MF.getTarget().Options.DisableFramePointerElim(MF) ||
       MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken();
 }
+
+uint64_t MipsFrameLowering::estimateStackSize(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  const TargetRegisterInfo &TRI = *MF.getTarget().getRegisterInfo();
+
+  int64_t Offset = 0;
+
+  // Iterate over fixed sized objects.
+  for (int I = MFI->getObjectIndexBegin(); I != 0; ++I)
+    Offset = std::max(Offset, -MFI->getObjectOffset(I));
+
+  // Conservatively assume all callee-saved registers will be saved.
+  for (const uint16_t *R = TRI.getCalleeSavedRegs(&MF); *R; ++R) {
+    unsigned Size = TRI.getMinimalPhysRegClass(*R)->getSize();
+    Offset = RoundUpToAlignment(Offset + Size, Size);
+  }
+
+  unsigned MaxAlign = MFI->getMaxAlignment();
+
+  // Check that MaxAlign is not zero if there is a stack object that is not a
+  // callee-saved spill.
+  assert(!MFI->getObjectIndexEnd() || MaxAlign);
+
+  // Iterate over other objects.
+  for (unsigned I = 0, E = MFI->getObjectIndexEnd(); I != E; ++I)
+    Offset = RoundUpToAlignment(Offset + MFI->getObjectSize(I), MaxAlign);
+
+  // Call frame.
+  if (MFI->adjustsStack() && hasReservedCallFrame(MF))
+    Offset = RoundUpToAlignment(Offset + MFI->getMaxCallFrameSize(),
+                                std::max(MaxAlign, getStackAlignment()));
+
+  return RoundUpToAlignment(Offset, getStackAlignment());
+}