commit a035726e5aae18bb9be1e61d9aef2a102c3b33ba
Author: Wei Mi <wmi@google.com>
Date:   Thu Mar 19 22:45:27 2020 -0700

    Revert "Generate Callee Saved Register (CSR) related cfi directives like .cfi_restore."
    
    This reverts commit 3c96d01d2e3de63304ca3429d349ec62ae2adef3. Got report that it caused test failures in libc++.

diff --git a/llvm/lib/CodeGen/CFIInstrInserter.cpp b/llvm/lib/CodeGen/CFIInstrInserter.cpp
index 2fc436e6349..ef548c84d3c 100644
--- a/llvm/lib/CodeGen/CFIInstrInserter.cpp
+++ b/llvm/lib/CodeGen/CFIInstrInserter.cpp
@@ -18,7 +18,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/SetOperations.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
@@ -77,10 +76,6 @@ class CFIInstrInserter : public MachineFunctionPass {
     unsigned IncomingCFARegister = 0;
     /// Value of cfa register valid at basic block exit.
     unsigned OutgoingCFARegister = 0;
-    /// Set of callee saved registers saved at basic block entry.
-    BitVector IncomingCSRSaved;
-    /// Set of callee saved registers saved at basic block exit.
-    BitVector OutgoingCSRSaved;
     /// If in/out cfa offset and register values for this block have already
     /// been set or not.
     bool Processed = false;
@@ -113,8 +108,7 @@ class CFIInstrInserter : public MachineFunctionPass {
     return -MBBVector[MBB->getNumber()].IncomingCFAOffset;
   }
 
-  void reportCFAError(const MBBCFAInfo &Pred, const MBBCFAInfo &Succ);
-  void reportCSRError(const MBBCFAInfo &Pred, const MBBCFAInfo &Succ);
+  void report(const MBBCFAInfo &Pred, const MBBCFAInfo &Succ);
   /// Go through each MBB in a function and check that outgoing offset and
   /// register of its predecessors match incoming offset and register of that
   /// MBB, as well as that incoming offset and register of its successors match
@@ -138,8 +132,6 @@ void CFIInstrInserter::calculateCFAInfo(MachineFunction &MF) {
   // function.
   unsigned InitialRegister =
       MF.getSubtarget().getFrameLowering()->getInitialCFARegister(MF);
-  const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
-  unsigned NumRegs = TRI.getNumRegs();
 
   // Initialize MBBMap.
   for (MachineBasicBlock &MBB : MF) {
@@ -149,8 +141,6 @@ void CFIInstrInserter::calculateCFAInfo(MachineFunction &MF) {
     MBBInfo.OutgoingCFAOffset = InitialOffset;
     MBBInfo.IncomingCFARegister = InitialRegister;
     MBBInfo.OutgoingCFARegister = InitialRegister;
-    MBBInfo.IncomingCSRSaved.resize(NumRegs);
-    MBBInfo.OutgoingCSRSaved.resize(NumRegs);
     MBBVector[MBB.getNumber()] = MBBInfo;
   }
 
@@ -169,11 +159,8 @@ void CFIInstrInserter::calculateOutgoingCFAInfo(MBBCFAInfo &MBBInfo) {
   int SetOffset = MBBInfo.IncomingCFAOffset;
   // Outgoing cfa register set by the block.
   unsigned SetRegister = MBBInfo.IncomingCFARegister;
-  MachineFunction *MF = MBBInfo.MBB->getParent();
-  const std::vector<MCCFIInstruction> &Instrs = MF->getFrameInstructions();
-  const TargetRegisterInfo &TRI = *MF->getSubtarget().getRegisterInfo();
-  unsigned NumRegs = TRI.getNumRegs();
-  BitVector CSRSaved(NumRegs), CSRRestored(NumRegs);
+  const std::vector<MCCFIInstruction> &Instrs =
+      MBBInfo.MBB->getParent()->getFrameInstructions();
 
   // Determine cfa offset and register set by the block.
   for (MachineInstr &MI : *MBBInfo.MBB) {
@@ -194,15 +181,6 @@ void CFIInstrInserter::calculateOutgoingCFAInfo(MBBCFAInfo &MBBInfo) {
         SetRegister = CFI.getRegister();
         SetOffset = CFI.getOffset();
         break;
-      case MCCFIInstruction::OpOffset:
-      case MCCFIInstruction::OpRegister:
-      case MCCFIInstruction::OpRelOffset:
-        CSRSaved.set(CFI.getRegister());
-        break;
-      case MCCFIInstruction::OpRestore:
-      case MCCFIInstruction::OpUndefined:
-        CSRRestored.set(CFI.getRegister());
-        break;
       case MCCFIInstruction::OpRememberState:
         // TODO: Add support for handling cfi_remember_state.
 #ifndef NDEBUG
@@ -221,7 +199,12 @@ void CFIInstrInserter::calculateOutgoingCFAInfo(MBBCFAInfo &MBBInfo) {
         break;
       // Other CFI directives do not affect CFA value.
       case MCCFIInstruction::OpSameValue:
+      case MCCFIInstruction::OpOffset:
+      case MCCFIInstruction::OpRelOffset:
       case MCCFIInstruction::OpEscape:
+      case MCCFIInstruction::OpRestore:
+      case MCCFIInstruction::OpUndefined:
+      case MCCFIInstruction::OpRegister:
       case MCCFIInstruction::OpWindowSave:
       case MCCFIInstruction::OpNegateRAState:
       case MCCFIInstruction::OpGnuArgsSize:
@@ -235,11 +218,6 @@ void CFIInstrInserter::calculateOutgoingCFAInfo(MBBCFAInfo &MBBInfo) {
   // Update outgoing CFA info.
   MBBInfo.OutgoingCFAOffset = SetOffset;
   MBBInfo.OutgoingCFARegister = SetRegister;
-
-  // Update outgoing CSR info.
-  MBBInfo.OutgoingCSRSaved = MBBInfo.IncomingCSRSaved;
-  MBBInfo.OutgoingCSRSaved |= CSRSaved;
-  MBBInfo.OutgoingCSRSaved.reset(CSRRestored);
 }
 
 void CFIInstrInserter::updateSuccCFAInfo(MBBCFAInfo &MBBInfo) {
@@ -258,7 +236,6 @@ void CFIInstrInserter::updateSuccCFAInfo(MBBCFAInfo &MBBInfo) {
       if (!SuccInfo.Processed) {
         SuccInfo.IncomingCFAOffset = CurrentInfo.OutgoingCFAOffset;
         SuccInfo.IncomingCFARegister = CurrentInfo.OutgoingCFARegister;
-        SuccInfo.IncomingCSRSaved = CurrentInfo.OutgoingCSRSaved;
         Stack.push_back(Succ);
       }
     }
@@ -310,23 +287,12 @@ bool CFIInstrInserter::insertCFIInstrs(MachineFunction &MF) {
           .addCFIIndex(CFIIndex);
       InsertedCFIInstr = true;
     }
-
-    BitVector SetDifference = PrevMBBInfo->OutgoingCSRSaved;
-    SetDifference.reset(MBBInfo.IncomingCSRSaved);
-    for (int Reg : SetDifference.set_bits()) {
-      unsigned CFIIndex =
-          MF.addFrameInst(MCCFIInstruction::createRestore(nullptr, Reg));
-      BuildMI(*MBBInfo.MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
-          .addCFIIndex(CFIIndex);
-      InsertedCFIInstr = true;
-    }
     PrevMBBInfo = &MBBInfo;
   }
   return InsertedCFIInstr;
 }
 
-void CFIInstrInserter::reportCFAError(const MBBCFAInfo &Pred,
-                                      const MBBCFAInfo &Succ) {
+void CFIInstrInserter::report(const MBBCFAInfo &Pred, const MBBCFAInfo &Succ) {
   errs() << "*** Inconsistent CFA register and/or offset between pred and succ "
             "***\n";
   errs() << "Pred: " << Pred.MBB->getName() << " #" << Pred.MBB->getNumber()
@@ -341,22 +307,6 @@ void CFIInstrInserter::reportCFAError(const MBBCFAInfo &Pred,
          << " incoming CFA Offset:" << Succ.IncomingCFAOffset << "\n";
 }
 
-void CFIInstrInserter::reportCSRError(const MBBCFAInfo &Pred,
-                                      const MBBCFAInfo &Succ) {
-  errs() << "*** Inconsistent CSR Saved between pred and succ in function "
-         << Pred.MBB->getParent()->getName() << " ***\n";
-  errs() << "Pred: " << Pred.MBB->getName() << " #" << Pred.MBB->getNumber()
-         << " outgoing CSR Saved: ";
-  for (int Reg : Pred.OutgoingCSRSaved.set_bits())
-    errs() << Reg << " ";
-  errs() << "\n";
-  errs() << "Succ: " << Succ.MBB->getName() << " #" << Succ.MBB->getNumber()
-         << " incoming CSR Saved: ";
-  for (int Reg : Succ.IncomingCSRSaved.set_bits())
-    errs() << Reg << " ";
-  errs() << "\n";
-}
-
 unsigned CFIInstrInserter::verify(MachineFunction &MF) {
   unsigned ErrorNum = 0;
   for (auto *CurrMBB : depth_first(&MF)) {
@@ -371,13 +321,7 @@ unsigned CFIInstrInserter::verify(MachineFunction &MF) {
         // we don't generate epilogues inside such blocks.
         if (SuccMBBInfo.MBB->succ_empty() && !SuccMBBInfo.MBB->isReturnBlock())
           continue;
-        reportCFAError(CurrMBBInfo, SuccMBBInfo);
-        ErrorNum++;
-      }
-      // Check that IncomingCSRSaved of every successor matches the
-      // OutgoingCSRSaved of CurrMBB
-      if (SuccMBBInfo.IncomingCSRSaved != CurrMBBInfo.OutgoingCSRSaved) {
-        reportCSRError(CurrMBBInfo, SuccMBBInfo);
+        report(CurrMBBInfo, SuccMBBInfo);
         ErrorNum++;
       }
     }
diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 1661497849d..4949d2f42c8 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -486,7 +486,7 @@ void X86FrameLowering::BuildCFI(MachineBasicBlock &MBB,
 
 void X86FrameLowering::emitCalleeSavedFrameMoves(
     MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
-    const DebugLoc &DL, bool IsPrologue) const {
+    const DebugLoc &DL) const {
   MachineFunction &MF = *MBB.getParent();
   MachineFrameInfo &MFI = MF.getFrameInfo();
   MachineModuleInfo &MMI = MF.getMMI();
@@ -501,15 +501,10 @@ void X86FrameLowering::emitCalleeSavedFrameMoves(
          I = CSI.begin(), E = CSI.end(); I != E; ++I) {
     int64_t Offset = MFI.getObjectOffset(I->getFrameIdx());
     unsigned Reg = I->getReg();
-    unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
 
-    if (IsPrologue) {
-      BuildCFI(MBB, MBBI, DL,
-               MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
-    } else {
-      BuildCFI(MBB, MBBI, DL,
-               MCCFIInstruction::createRestore(nullptr, DwarfReg));
-    }
+    unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
+    BuildCFI(MBB, MBBI, DL,
+             MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
   }
 }
 
@@ -1680,7 +1675,7 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
     }
 
     // Emit DWARF info specifying the offsets of the callee-saved registers.
-    emitCalleeSavedFrameMoves(MBB, MBBI, DL, true);
+    emitCalleeSavedFrameMoves(MBB, MBBI, DL);
   }
 
   // X86 Interrupt handling function cannot assume anything about the direction
@@ -1830,8 +1825,6 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
   }
   uint64_t SEHStackAllocAmt = NumBytes;
 
-  // AfterPop is the position to insert .cfi_restore.
-  MachineBasicBlock::iterator AfterPop = MBBI;
   if (HasFP) {
     // Pop EBP.
     BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::POP64r : X86::POP32r),
@@ -1842,13 +1835,6 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
           TRI->getDwarfRegNum(Is64Bit ? X86::RSP : X86::ESP, true);
       BuildCFI(MBB, MBBI, DL, MCCFIInstruction::createDefCfa(
                                   nullptr, DwarfStackPtr, -SlotSize));
-      if (!MBB.succ_empty() && !MBB.isReturnBlock()) {
-        unsigned DwarfFramePtr = TRI->getDwarfRegNum(MachineFramePtr, true);
-        BuildCFI(MBB, AfterPop, DL,
-                 MCCFIInstruction::createRestore(nullptr, DwarfFramePtr));
-        --MBBI;
-        --AfterPop;
-      }
       --MBBI;
     }
   }
@@ -1948,13 +1934,6 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
     }
   }
 
-  // Emit DWARF info specifying the restores of the callee-saved registers.
-  // For epilogue with return inside or being other block without successor,
-  // no need to generate .cfi_restore for callee-saved registers.
-  if (NeedsDwarfCFI && !MBB.succ_empty() && !MBB.isReturnBlock()) {
-    emitCalleeSavedFrameMoves(MBB, AfterPop, DL, false);
-  }
-
   if (Terminator == MBB.end() || !isTailCallOpcode(Terminator->getOpcode())) {
     // Add the return addr area delta back since we are not tail calling.
     int Offset = -1 * X86FI->getTCReturnAddrDelta();
diff --git a/llvm/lib/Target/X86/X86FrameLowering.h b/llvm/lib/Target/X86/X86FrameLowering.h
index 43c81d9d5a4..c7b41543c50 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.h
+++ b/llvm/lib/Target/X86/X86FrameLowering.h
@@ -60,7 +60,7 @@ public:
 
   void emitCalleeSavedFrameMoves(MachineBasicBlock &MBB,
                                  MachineBasicBlock::iterator MBBI,
-                                 const DebugLoc &DL, bool IsPrologue) const;
+                                 const DebugLoc &DL) const;
 
   /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
   /// the function.
diff --git a/llvm/test/CodeGen/X86/cfi-epilogue-with-return.mir b/llvm/test/CodeGen/X86/cfi-epilogue-with-return.mir
deleted file mode 100644
index 583e54b097f..00000000000
--- a/llvm/test/CodeGen/X86/cfi-epilogue-with-return.mir
+++ /dev/null
@@ -1,48 +0,0 @@
-# RUN: llc -o - %s -mtriple=x86_64-- -run-pass=prologepilog 2>&1 | FileCheck %s
---- |
-  define i64 @_Z3foob(i1 zeroext %cond) #0 {
-    ret i64 0
-  }
-  attributes #0 = {"frame-pointer"="all"}
-...
----
-# If the epilogue bb.1 is a return block, no .cfi_restore is
-# needed in it.
-# CHECK:    bb.1:
-# CHECK-NOT:  CFI_INSTRUCTION restore
-# CHECK:      RET 0
-# CHECK:    bb.2:
-# CHECK:      RET 0
-name:            _Z3foob
-alignment:       16
-tracksRegLiveness: true
-liveins:
-  - { reg: '$edi' }
-frameInfo:
-  maxAlignment:    1
-  hasCalls:        true
-  savePoint:       '%bb.1'
-  restorePoint:    '%bb.1'
-machineFunctionInfo: {}
-body:             |
-  bb.0:
-    liveins: $edi
-  
-    TEST8rr renamable $dil, renamable $dil, implicit-def $eflags, implicit killed $edi
-    JCC_1 %bb.2, 4, implicit killed $eflags
-    JMP_1 %bb.1
-  
-  bb.1:
-    renamable $rbx = IMPLICIT_DEF
-    renamable $r14 = IMPLICIT_DEF
-    renamable $r15 = IMPLICIT_DEF
-    renamable $r12 = IMPLICIT_DEF
-    renamable $r13 = IMPLICIT_DEF
-    dead $eax = MOV32r0 implicit-def dead $eflags, implicit-def $rax
-    RET 0, killed $rax
-  
-  bb.2:
-    dead $eax = MOV32r0 implicit-def dead $eflags, implicit-def $rax
-    RET 0, killed $rax
-
-...
diff --git a/llvm/test/CodeGen/X86/cfi-epilogue-without-return.mir b/llvm/test/CodeGen/X86/cfi-epilogue-without-return.mir
deleted file mode 100644
index 8f047214896..00000000000
--- a/llvm/test/CodeGen/X86/cfi-epilogue-without-return.mir
+++ /dev/null
@@ -1,53 +0,0 @@
-# RUN: llc -o - %s -mtriple=x86_64-- -run-pass=prologepilog 2>&1 | FileCheck %s
---- |
-  declare dso_local void @_Z3goov()
-  define i64 @_Z3foob(i1 zeroext %cond) #0 {
-    ret i64 0
-  }
-  attributes #0 = {"frame-pointer"="all"}
-...
----
-# If the epilogue bb.1.if.then is not a return block, .cfi_restore is
-# needed in it, otherwise bb.2.return will see different outgoing CFI
-# information from its predecessors.
-# CHECK:    bb.1:
-# CHECK:      CFI_INSTRUCTION restore $rbx
-# CHECK-NEXT: CFI_INSTRUCTION restore $r12
-# CHECK-NEXT: CFI_INSTRUCTION restore $r13
-# CHECK-NEXT: CFI_INSTRUCTION restore $r14
-# CHECK-NEXT: CFI_INSTRUCTION restore $r15
-# CHECK-NEXT: CFI_INSTRUCTION restore $rbp
-# CHECK-NOT:  RET 0
-# CHECK:    bb.2:
-# CHECK:      RET 0
-name:            _Z3foob
-alignment:       16
-tracksRegLiveness: true
-liveins:
-  - { reg: '$edi' }
-frameInfo:
-  maxAlignment:    1
-  hasCalls:        true
-  savePoint:       '%bb.1'
-  restorePoint:    '%bb.1'
-machineFunctionInfo: {}
-body:             |
-  bb.0:
-    liveins: $edi
-  
-    TEST8rr renamable $dil, renamable $dil, implicit-def $eflags, implicit killed $edi
-    JCC_1 %bb.2, 4, implicit killed $eflags
-    JMP_1 %bb.1
-  
-  bb.1:
-    renamable $rbx = IMPLICIT_DEF
-    renamable $r14 = IMPLICIT_DEF
-    renamable $r15 = IMPLICIT_DEF
-    renamable $r12 = IMPLICIT_DEF
-    renamable $r13 = IMPLICIT_DEF
-  
-  bb.2:
-    dead $eax = MOV32r0 implicit-def dead $eflags, implicit-def $rax
-    RET 0, killed $rax
-
-...
diff --git a/llvm/test/CodeGen/X86/cfi-inserter-callee-save-register.mir b/llvm/test/CodeGen/X86/cfi-inserter-callee-save-register.mir
deleted file mode 100644
index b17c9a67abb..00000000000
--- a/llvm/test/CodeGen/X86/cfi-inserter-callee-save-register.mir
+++ /dev/null
@@ -1,34 +0,0 @@
-# RUN: llc -o - %s -mtriple=x86_64-- -verify-cfiinstrs \
-# RUN:     -run-pass=cfi-instr-inserter 2>&1 | FileCheck %s
-# Test that CFI inserter inserts .cfi_restore properly for
-# callee saved registers.
---- |
-  define void @foo() {
-    ret void
-  }
-...
----
-# CHECK:      bb.3:
-# CHECK:      CFI_INSTRUCTION restore $rbx
-# CHECK-NEXT: CFI_INSTRUCTION restore $rbp
-name:            foo
-body:             |
-  bb.0:
-    TEST8rr renamable $dil, renamable $dil, implicit-def $eflags, implicit killed $edi
-    JCC_1 %bb.2, 5, implicit killed $eflags
-
-  bb.1:
-    JMP_1 %bb.3
-
-  bb.2:
-    CFI_INSTRUCTION def_cfa_offset 16
-    CFI_INSTRUCTION offset $rbp, -16
-    CFI_INSTRUCTION def_cfa_register $rbp
-    CFI_INSTRUCTION offset $rbx, -24
-    CFI_INSTRUCTION def_cfa $rsp, 8
-    RET 0, $rax
-
-  bb.3:
-    RET 0, $rax
-
-...
diff --git a/llvm/test/CodeGen/X86/cfi-inserter-verify-inconsistent-csr.mir b/llvm/test/CodeGen/X86/cfi-inserter-verify-inconsistent-csr.mir
deleted file mode 100644
index 63957ae5229..00000000000
--- a/llvm/test/CodeGen/X86/cfi-inserter-verify-inconsistent-csr.mir
+++ /dev/null
@@ -1,28 +0,0 @@
-# RUN: not --crash llc -o - %s -mtriple=x86_64-- -verify-cfiinstrs \
-# RUN:     -run-pass=cfi-instr-inserter 2>&1 | FileCheck %s
-# Test that CFI verifier finds inconsistent csr saved set between bb.end and
-# one of its precedessors.
---- |
-  define void @inconsistentCSR() {
-  entry:
-    br label %then
-  then:
-    br label %end
-  end:
-    ret void
-  }
-...
----
-# CHECK: *** Inconsistent CSR Saved between pred and succ in function inconsistentCSR ***
-# CHECK: LLVM ERROR: Found 1 in/out CFI information errors.
-name: inconsistentCSR
-body: |
-  bb.0.entry:
-    JCC_1 %bb.2, 5, implicit undef $eflags
-
-  bb.1.then:
-    CFI_INSTRUCTION offset $rbp, -16
-
-  bb.2.end:
-    RET 0
-...