[PATCH] D69906: [ARM] Track epilogue instructions with FrameDestroy flag (NFC)

[Oliver Stannard (Linaro) via Phabricator via llvm-commits]

ostannard created this revision.
ostannard added a reviewer: sdesmalen.
Herald added subscribers: hiraditya, kristof.beyls.
Herald added a project: LLVM.

Rather than trying to work out which instructions are part of the epilogue by examining them, we can just mark them with the FrameDestroy flag, like we do in the AArch64 backend.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D69906

Files:
  llvm/lib/Target/ARM/ARMFrameLowering.cpp


Index: llvm/lib/Target/ARM/ARMFrameLowering.cpp
===================================================================
--- llvm/lib/Target/ARM/ARMFrameLowering.cpp
+++ llvm/lib/Target/ARM/ARMFrameLowering.cpp
@@ -142,27 +142,6 @@
   return hasReservedCallFrame(MF) || MF.getFrameInfo().hasVarSizedObjects();
 }
 
-static bool isCSRestore(MachineInstr &MI, const ARMBaseInstrInfo &TII,
-                        const MCPhysReg *CSRegs) {
-  // Integer spill area is handled with "pop".
-  if (isPopOpcode(MI.getOpcode())) {
-    // The first two operands are predicates. The last two are
-    // imp-def and imp-use of SP. Check everything in between.
-    for (int i = 5, e = MI.getNumOperands(); i != e; ++i)
-      if (!isCalleeSavedRegister(MI.getOperand(i).getReg(), CSRegs))
-        return false;
-    return true;
-  }
-  if ((MI.getOpcode() == ARM::LDR_POST_IMM ||
-       MI.getOpcode() == ARM::LDR_POST_REG ||
-       MI.getOpcode() == ARM::t2LDR_POST) &&
-      isCalleeSavedRegister(MI.getOperand(0).getReg(), CSRegs) &&
-      MI.getOperand(1).getReg() == ARM::SP)
-    return true;
-
-  return false;
-}
-
 static void emitRegPlusImmediate(
     bool isARM, MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
     const DebugLoc &dl, const ARMBaseInstrInfo &TII, unsigned DestReg,
@@ -796,12 +775,12 @@
       emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes - ArgRegsSaveSize);
   } else {
     // Unwind MBBI to point to first LDR / VLDRD.
-    const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF);
     if (MBBI != MBB.begin()) {
       do {
         --MBBI;
-      } while (MBBI != MBB.begin() && isCSRestore(*MBBI, TII, CSRegs));
-      if (!isCSRestore(*MBBI, TII, CSRegs))
+      } while (MBBI != MBB.begin() &&
+               MBBI->getFlag(MachineInstr::FrameDestroy));
+      if (!MBBI->getFlag(MachineInstr::FrameDestroy))
         ++MBBI;
     }
 
@@ -1119,7 +1098,8 @@
     if (Regs.size() > 1 || LdrOpc == 0) {
       MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(LdmOpc), ARM::SP)
                                     .addReg(ARM::SP)
-                                    .add(predOps(ARMCC::AL));
+                                    .add(predOps(ARMCC::AL))
+                                    .setMIFlags(MachineInstr::FrameDestroy);
       for (unsigned i = 0, e = Regs.size(); i < e; ++i)
         MIB.addReg(Regs[i], getDefRegState(true));
       if (DeleteRet) {
@@ -1137,7 +1117,8 @@
       MachineInstrBuilder MIB =
         BuildMI(MBB, MI, DL, TII.get(LdrOpc), Regs[0])
           .addReg(ARM::SP, RegState::Define)
-          .addReg(ARM::SP);
+          .addReg(ARM::SP)
+          .setMIFlags(MachineInstr::FrameDestroy);
       // ARM mode needs an extra reg0 here due to addrmode2. Will go away once
       // that refactoring is complete (eventually).
       if (LdrOpc == ARM::LDR_POST_REG || LdrOpc == ARM::LDR_POST_IMM) {


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