[llvm] [RISCV][CFI] add function epilogue cfi information (PR #110234)

[Craig Topper via llvm-commits]

================
@@ -810,50 +878,58 @@ void RISCVFrameLowering::emitEpilogue(MachineFunction &MF,
   // normally it's just checking the variable sized object is present or not
   // is enough, but we also don't preserve that at prologue/epilogue when
   // have vector objects in stack.
-  if (RI->hasStackRealignment(MF) || MFI.hasVarSizedObjects() ||
-      !hasReservedCallFrame(MF)) {
-    assert(hasFP(MF) && "frame pointer should not have been eliminated");
+  if (restoreFP) {
     RI->adjustReg(MBB, LastFrameDestroy, DL, SPReg, FPReg,
-                  StackOffset::getFixed(-FPOffset),
-                  MachineInstr::FrameDestroy, getStackAlign());
-  } else {
-    if (RVVStackSize)
-      adjustStackForRVV(MF, MBB, LastFrameDestroy, DL, RVVStackSize,
-                        MachineInstr::FrameDestroy);
-  }
-
-  uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
-  if (FirstSPAdjustAmount) {
-    uint64_t SecondSPAdjustAmount =
-        getStackSizeWithRVVPadding(MF) - FirstSPAdjustAmount;
-    assert(SecondSPAdjustAmount > 0 &&
-           "SecondSPAdjustAmount should be greater than zero");
+                  StackOffset::getFixed(-FPOffset), MachineInstr::FrameDestroy,
+                  getStackAlign());
 
-    RI->adjustReg(MBB, LastFrameDestroy, DL, SPReg, SPReg,
-                  StackOffset::getFixed(SecondSPAdjustAmount),
-                  MachineInstr::FrameDestroy, getStackAlign());
+    unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfa(
+        nullptr, RI->getDwarfRegNum(SPReg, true), RealStackSize));
+    BuildMI(MBB, LastFrameDestroy, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+        .addCFIIndex(CFIIndex)
+        .setMIFlag(MachineInstr::FrameDestroy);
   }
 
-  if (FirstSPAdjustAmount)
-    StackSize = FirstSPAdjustAmount;
-
-  if (RVFI->isPushable(MF) && MBBI != MBB.end() &&
-      MBBI->getOpcode() == RISCV::CM_POP) {
+  bool ApplyPop = RVFI->isPushable(MF) && MBBI != MBB.end() &&
+                  MBBI->getOpcode() == RISCV::CM_POP;
+  if (ApplyPop) {
     // Use available stack adjustment in pop instruction to deallocate stack
     // space. Align the stack size down to a multiple of 16. This is needed for
     // RVE.
     // FIXME: Can we increase the stack size to a multiple of 16 instead?
     uint64_t Spimm = std::min(alignDown(StackSize, 16), (uint64_t)48);
     MBBI->getOperand(1).setImm(Spimm);
     StackSize -= Spimm;
+
+    if (StackSize != 0)
+      deallocateStack(MF, MBB, MBBI, DL, StackSize,
+                      /*stack_adj of cm.pop instr*/ RealStackSize - StackSize);
+
+    // Update CFA offset. After CM_POP SP should be equal to CFA, so CFA offset
+    // is zero.
+    MBBI = std::next(MBBI);
----------------
topperc wrote:

++MBBI?

https://github.com/llvm/llvm-project/pull/110234