1 files changed, 73 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index b9920b1b84c..278e4f910d4 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -1135,6 +1135,79 @@ int X86FrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
   return getFrameIndexOffset(MF, FI);
 }
 
+// Simplified from getFrameIndexOffset keeping only StackPointer cases
+int X86FrameLowering::getFrameIndexOffsetFromSP(const MachineFunction &MF, int FI) const {
+  const X86RegisterInfo *RegInfo =
+    static_cast<const X86RegisterInfo*>(MF.getSubtarget().getRegisterInfo());
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  const uint64_t StackSize = MFI->getStackSize(); //not including dynamic realign
+
+  {
+#ifndef NDEBUG
+    // Note: LLVM arranges the stack as:
+    // Args > Saved RetPC (<--FP) > CSRs > dynamic alignment (<--BP)
+    //      > "Stack Slots" (<--SP)
+    // We can always address StackSlots from RSP.  We can usually (unless
+    // needsStackRealignment) address CSRs from RSP, but sometimes need to
+    // address them from RBP.  FixedObjects can be placed anywhere in the stack
+    // frame depending on their specific requirements (i.e. we can actually
+    // refer to arguments to the function which are stored in the *callers*
+    // frame).  As a result, THE RESULT OF THIS CALL IS MEANINGLESS FOR CSRs
+    // AND FixedObjects IFF needsStackRealignment or hasVarSizedObject.
+        
+    assert(!RegInfo->hasBasePointer(MF) && "we don't handle this case");
+
+    // We don't handle tail calls, and shouldn't be seeing them
+    // either.
+    int TailCallReturnAddrDelta =
+        MF.getInfo<X86MachineFunctionInfo>()->getTCReturnAddrDelta();
+    assert(!(TailCallReturnAddrDelta < 0) && "we don't handle this case!");
+#endif
+  }
+
+  // This is how the math works out:
+  //
+  //  %rsp grows (i.e. gets lower) left to right. Each box below is
+  //  one word (eight bytes).  Obj0 is the stack slot we're trying to
+  //  get to.
+  //
+  //    ----------------------------------
+  //    | BP | Obj0 | Obj1 | ... | ObjN |
+  //    ----------------------------------
+  //    ^    ^      ^                   ^
+  //    A    B      C                   E
+  //
+  // A is the incoming stack pointer.
+  // (B - A) is the local area offset (-8 for x86-64) [1]
+  // (C - A) is the Offset returned by MFI->getObjectOffset for Obj0 [2]
+  //
+  // |(E - B)| is the StackSize (absolute value, positive).  For a
+  // stack that grown down, this works out to be (B - E). [3]
+  //
+  // E is also the value of %rsp after stack has been set up, and we
+  // want (C - E) -- the value we can add to %rsp to get to Obj0.  Now
+  // (C - E) == (C - A) - (B - A) + (B - E)
+  //            { Using [1], [2] and [3] above }
+  //         == getObjectOffset - LocalAreaOffset + StackSize
+  //
+
+  // Get the Offset from the StackPointer
+  int Offset = MFI->getObjectOffset(FI) - getOffsetOfLocalArea();
+
+  return Offset + StackSize;
+}
+// Simplified from getFrameIndexReference keeping only StackPointer cases
+int X86FrameLowering::getFrameIndexReferenceFromSP(const MachineFunction &MF, int FI,
+                                                  unsigned &FrameReg) const {
+  const X86RegisterInfo *RegInfo =
+    static_cast<const X86RegisterInfo*>(MF.getSubtarget().getRegisterInfo());
+
+  assert(!RegInfo->hasBasePointer(MF) && "we don't handle this case");
+
+  FrameReg = RegInfo->getStackRegister();
+  return getFrameIndexOffsetFromSP(MF, FI);
+}
+
 bool X86FrameLowering::assignCalleeSavedSpillSlots(
     MachineFunction &MF, const TargetRegisterInfo *TRI,
     std::vector<CalleeSavedInfo> &CSI) const {