dpu: llvm: fix issue with stack size info

In case of a leaf function, we do not move the Stack Pointer.
To do so previously, we tricked the MachineFrameInfo by setting the StackSize to 0. This worked, but when emiting the .stack_sizes section, the information was incorrect.

Now StackSize in MachineFrameInfo is always correct. We are using the MachineFrameInfo::hasCalls method to check if we need to change the offset when doing stack accesses (in DPUMachineFunctionInfo::getOffsetFromFrameIndex).

fix #1

Author: jchauzi

llvm/lib/Target/DPU/DPUFrameLowering.cpp

@@ -52,19 +52,21 @@ void DPUFrameLowering::emitPrologue(MachineFunction &MF,
   const DPUInstrInfo &TII =
       *static_cast<const DPUInstrInfo *>(STI.getInstrInfo());
   DebugLoc DL;
-  unsigned CFIIndex, StackSize;
+  unsigned CFIIndex, StackSize, ActualStackSize;
 
   if (!MFI.hasCalls()) {
     StackSize = 0;
+    ActualStackSize = MFI.getStackSize();
   } else {
     // We reserve manually 8 bytes to store d22 (r22r23) at the end of the stack
     // for debug purpose. Not at the beginning because we do not have a frame
     // pointer (pointing at the beginning of the stack) but only a stack pointer
     // (pointing at the end of the stack)
     StackSize =
         alignTo(MFI.getStackSize() + STACK_SIZE_FOR_D22, getStackAlignment());
+    ActualStackSize = StackSize;
   }
-  MFI.setStackSize(StackSize);
+  MFI.setStackSize(ActualStackSize);
 
   CFIIndex =
       MF.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, StackSize));

llvm/lib/Target/DPU/DPUMachineFunctionInfo.cpp

@@ -22,7 +22,9 @@ int DPUMachineFunctionInfo::getOffsetFromFrameIndex(int FrameIndex) {
   frameIndexOffsetSet.insert(FrameIndex);
   if (FrameIndex < 0)
     Offset -= STACK_SIZE_FOR_D22;
-  Offset -= MFI.getStackSize();
+  if (MFI.hasCalls()) {
+    Offset -= MFI.getStackSize();
+  }
   MFI.setObjectOffset(FrameIndex, Offset);
   return Offset;
 }