From 064eb5a1777048c653f6df3975654ac0787249e5 Mon Sep 17 00:00:00 2001
From: Jonathan Roelofs <jonathan@codesourcery.com>
Date: Tue, 5 Aug 2014 17:36:05 +0000
Subject: Revert r214881 because it broke lots of build-bots

llvm-svn: 214893
---
 llvm/lib/Target/ARM/Thumb1FrameLowering.cpp | 78 +++++++----------------------
 1 file changed, 19 insertions(+), 59 deletions(-)

(limited to 'llvm/lib/Target/ARM/Thumb1FrameLowering.cpp')

diff --git a/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp b/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
index 6deab4f0887..05852d814aa 100644
--- a/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
+++ b/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
@@ -388,65 +388,28 @@ void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF,
     }
   }
 
-  bool IsV4PopReturn = false;
-  for (const CalleeSavedInfo &CSI : MFI->getCalleeSavedInfo())
-    if (CSI.getReg() == ARM::LR)
-      IsV4PopReturn = true;
-  IsV4PopReturn &= STI.hasV4TOps() && !STI.hasV5TOps();
-
-  // Unlike T2 and ARM mode, the T1 pop instruction cannot restore
-  // to LR, and we can't pop the value directly to the PC since
-  // we need to update the SP after popping the value. So instead
-  // we have to emit:
-  //   POP {r3}
-  //   ADD sp, #offset
-  //   BX r3
-  // If this would clobber a return value, then generate this sequence instead:
-  //   MOV ip, r3
-  //   POP {r3}
-  //   ADD sp, #offset
-  //   MOV lr, r3
-  //   MOV r3, ip
-  //   BX lr
-  if (ArgRegsSaveSize || IsV4PopReturn) {
+  if (ArgRegsSaveSize) {
+    // Unlike T2 and ARM mode, the T1 pop instruction cannot restore
+    // to LR, and we can't pop the value directly to the PC since
+    // we need to update the SP after popping the value. Therefore, we
+    // pop the old LR into R3 as a temporary.
+
     // Get the last instruction, tBX_RET
     MBBI = MBB.getLastNonDebugInstr();
     assert (MBBI->getOpcode() == ARM::tBX_RET);
-    DebugLoc dl = MBBI->getDebugLoc();
-
-    if (AFI->getReturnRegsCount() <= 3) {
-      // Epilogue: pop saved LR to R3 and branch off it. 
-      AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
-        .addReg(ARM::R3, RegState::Define);
-
-      emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize);
-
-      MachineInstrBuilder MIB =
-        BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX))
-        .addReg(ARM::R3, RegState::Kill);
-      AddDefaultPred(MIB);
-      MIB.copyImplicitOps(&*MBBI);
-      // erase the old tBX_RET instruction
-      MBB.erase(MBBI);
-    } else {
-      AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
-        .addReg(ARM::R12, RegState::Define)
-        .addReg(ARM::R3, RegState::Kill));
-
-      AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
-        .addReg(ARM::R3, RegState::Define);
-
-      emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize);
-
-      AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
-        .addReg(ARM::LR, RegState::Define)
-        .addReg(ARM::R3, RegState::Kill));
-
-      AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr))
-        .addReg(ARM::R3, RegState::Define)
-        .addReg(ARM::R12, RegState::Kill));
-      // Keep the tBX_RET instruction
-    }
+    // Epilogue for vararg functions: pop LR to R3 and branch off it.
+    AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
+      .addReg(ARM::R3, RegState::Define);
+
+    emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize);
+
+    MachineInstrBuilder MIB =
+      BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX_RET_vararg))
+      .addReg(ARM::R3, RegState::Kill);
+    AddDefaultPred(MIB);
+    MIB.copyImplicitOps(&*MBBI);
+    // erase the old tBX_RET instruction
+    MBB.erase(MBBI);
   }
 }
 
@@ -513,9 +476,6 @@ restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
       // Special epilogue for vararg functions. See emitEpilogue
       if (isVarArg)
         continue;
-      // ARMv4T requires BX, see emitEpilogue
-      if (STI.hasV4TOps() && !STI.hasV5TOps())
-        continue;
       Reg = ARM::PC;
       (*MIB).setDesc(TII.get(ARM::tPOP_RET));
       MIB.copyImplicitOps(&*MI);
-- 
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