Generate native unwind info on Win64

This patch enables LLVM to emit Win64-native unwind info rather than
DWARF CFI.  It handles all corner cases (I hope), including stack
realignment.

Because the unwind info is not flexible enough to describe stack frames
with a gap of unknown size in the middle, such as the one caused by
stack realignment, I modified register spilling code to place all spills
into the fixed frame slots, so that they can be accessed relative to the
frame pointer.

Patch by Vadim Chugunov!

Reviewed By: rnk

Differential Revision: http://reviews.llvm.org/D4081

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211399 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 77 insertions, 68 deletions

diff --git a/lib/CodeGen/AsmPrinter/Win64Exception.cpp b/lib/CodeGen/AsmPrinter/Win64Exception.cpp
index 4768a43e9a..89bf89fdd7 100644
--- a/lib/CodeGen/AsmPrinter/Win64Exception.cpp
+++ b/lib/CodeGen/AsmPrinter/Win64Exception.cpp
@@ -77,9 +77,9 @@ void Win64Exception::beginFunction(const MachineFunction *MF) {
   if (!shouldEmitPersonality)
     return;
 
-  MCSymbol *GCCHandlerSym =
-    Asm->GetExternalSymbolSymbol("_GCC_specific_handler");
-  Asm->OutStreamer.EmitWin64EHHandler(GCCHandlerSym, true, true);
+  const MCSymbol *PersHandlerSym =
+      TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, MMI);
+  Asm->OutStreamer.EmitWin64EHHandler(PersHandlerSym, true, true);
 
   Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
                                                 Asm->getFunctionNumber()));
@@ -98,15 +98,8 @@ void Win64Exception::endFunction(const MachineFunction *) {
   MMI->TidyLandingPads();
 
   if (shouldEmitPersonality) {
-    const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
-    const Function *Per = MMI->getPersonalities()[MMI->getPersonalityIndex()];
-    const MCSymbol *Sym =
-        TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, MMI);
-
     Asm->OutStreamer.PushSection();
     Asm->OutStreamer.EmitWin64EHHandlerData();
-    Asm->OutStreamer.EmitValue(MCSymbolRefExpr::Create(Sym, Asm->OutContext),
-                               4);
     emitExceptionTable();
     Asm->OutStreamer.PopSection();
   }
diff --git a/lib/CodeGen/MachineFunction.cpp b/lib/CodeGen/MachineFunction.cpp
index eb3d71fef5..6138aef4ad 100644
--- a/lib/CodeGen/MachineFunction.cpp
+++ b/lib/CodeGen/MachineFunction.cpp
@@ -457,7 +457,7 @@ unsigned MachineFunction::addLiveIn(unsigned PReg,
 /// getJTISymbol - Return the MCSymbol for the specified non-empty jump table.
 /// If isLinkerPrivate is specified, an 'l' label is returned, otherwise a
 /// normal 'L' label is returned.
-MCSymbol *MachineFunction::getJTISymbol(unsigned JTI, MCContext &Ctx, 
+MCSymbol *MachineFunction::getJTISymbol(unsigned JTI, MCContext &Ctx,
                                         bool isLinkerPrivate) const {
   const DataLayout *DL = getTarget().getDataLayout();
   assert(JumpTableInfo && "No jump tables");
@@ -530,10 +530,9 @@ int MachineFrameInfo::CreateStackObject(uint64_t Size, unsigned Alignment,
 ///
 int MachineFrameInfo::CreateSpillStackObject(uint64_t Size,
                                              unsigned Alignment) {
-  Alignment =
-    clampStackAlignment(!getFrameLowering()->isStackRealignable() ||
-                          !RealignOption,
-                        Alignment, getFrameLowering()->getStackAlignment()); 
+  Alignment = clampStackAlignment(
+      !getFrameLowering()->isStackRealignable() || !RealignOption, Alignment,
+      getFrameLowering()->getStackAlignment());
   CreateStackObject(Size, Alignment, true);
   int Index = (int)Objects.size() - NumFixedObjects - 1;
   ensureMaxAlignment(Alignment);
@@ -548,10 +547,9 @@ int MachineFrameInfo::CreateSpillStackObject(uint64_t Size,
 int MachineFrameInfo::CreateVariableSizedObject(unsigned Alignment,
                                                 const AllocaInst *Alloca) {
   HasVarSizedObjects = true;
-  Alignment =
-    clampStackAlignment(!getFrameLowering()->isStackRealignable() ||
-                          !RealignOption,
-                        Alignment, getFrameLowering()->getStackAlignment()); 
+  Alignment = clampStackAlignment(
+      !getFrameLowering()->isStackRealignable() || !RealignOption, Alignment,
+      getFrameLowering()->getStackAlignment());
   Objects.push_back(StackObject(0, Alignment, 0, false, false, Alloca));
   ensureMaxAlignment(Alignment);
   return (int)Objects.size()-NumFixedObjects-1;
@@ -571,16 +569,30 @@ int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset,
   // object is 16-byte aligned.
   unsigned StackAlign = getFrameLowering()->getStackAlignment();
   unsigned Align = MinAlign(SPOffset, StackAlign);
-  Align =
-    clampStackAlignment(!getFrameLowering()->isStackRealignable() ||
-                          !RealignOption,
-                        Align, getFrameLowering()->getStackAlignment()); 
+  Align = clampStackAlignment(!getFrameLowering()->isStackRealignable() ||
+                                  !RealignOption,
+                              Align, getFrameLowering()->getStackAlignment());
   Objects.insert(Objects.begin(), StackObject(Size, Align, SPOffset, Immutable,
                                               /*isSS*/   false,
                                               /*Alloca*/ nullptr));
   return -++NumFixedObjects;
 }
 
+/// CreateFixedSpillStackObject - Create a spill slot at a fixed location
+/// on the stack.  Returns an index with a negative value.
+int MachineFrameInfo::CreateFixedSpillStackObject(uint64_t Size,
+                                                  int64_t SPOffset) {
+  unsigned StackAlign = getFrameLowering()->getStackAlignment();
+  unsigned Align = MinAlign(SPOffset, StackAlign);
+  Align = clampStackAlignment(!getFrameLowering()->isStackRealignable() ||
+                                  !RealignOption,
+                              Align, getFrameLowering()->getStackAlignment());
+  Objects.insert(Objects.begin(), StackObject(Size, Align, SPOffset,
+                                              /*Immutable*/ true,
+                                              /*isSS*/ true,
+                                              /*Alloca*/ nullptr));
+  return -++NumFixedObjects;
+}
 
 BitVector
 MachineFrameInfo::getPristineRegs(const MachineBasicBlock *MBB) const {
@@ -849,11 +861,10 @@ static bool CanShareConstantPoolEntry(const Constant *A, const Constant *B,
   if (isa<StructType>(A->getType()) || isa<ArrayType>(A->getType()) ||
       isa<StructType>(B->getType()) || isa<ArrayType>(B->getType()))
     return false;
-  
+
   // For now, only support constants with the same size.
   uint64_t StoreSize = TD->getTypeStoreSize(A->getType());
-  if (StoreSize != TD->getTypeStoreSize(B->getType()) || 
-      StoreSize > 128)
+  if (StoreSize != TD->getTypeStoreSize(B->getType()) || StoreSize > 128)
     return false;
 
   Type *IntTy = IntegerType::get(A->getContext(), StoreSize*8);
@@ -882,7 +893,7 @@ static bool CanShareConstantPoolEntry(const Constant *A, const Constant *B,
 /// an existing one.  User must specify the log2 of the minimum required
 /// alignment for the object.
 ///
-unsigned MachineConstantPool::getConstantPoolIndex(const Constant *C, 
+unsigned MachineConstantPool::getConstantPoolIndex(const Constant *C,
                                                    unsigned Alignment) {
   assert(Alignment && "Alignment must be specified!");
   if (Alignment > PoolAlignment) PoolAlignment = Alignment;
diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp
index 1ba2c7418f..69ff6b3d92 100644
--- a/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/lib/CodeGen/PrologEpilogInserter.cpp
@@ -268,51 +268,56 @@ void PEI::calculateCalleeSavedRegisters(MachineFunction &F) {
     }
   }
 
-  if (CSI.empty())
-    return;   // Early exit if no callee saved registers are modified!
-
-  unsigned NumFixedSpillSlots;
-  const TargetFrameLowering::SpillSlot *FixedSpillSlots =
-    TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
-
-  // Now that we know which registers need to be saved and restored, allocate
-  // stack slots for them.
-  for (std::vector<CalleeSavedInfo>::iterator
-         I = CSI.begin(), E = CSI.end(); I != E; ++I) {
-    unsigned Reg = I->getReg();
-    const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
-
-    int FrameIdx;
-    if (RegInfo->hasReservedSpillSlot(F, Reg, FrameIdx)) {
-      I->setFrameIdx(FrameIdx);
-      continue;
-    }
+  if (!TFI->assignCalleeSavedSpillSlots(F, RegInfo, CSI)) {
+    // If target doesn't implement this, use generic code.
+
+    if (CSI.empty())
+      return; // Early exit if no callee saved registers are modified!
+
+    unsigned NumFixedSpillSlots;
+    const TargetFrameLowering::SpillSlot *FixedSpillSlots =
+        TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
+
+    // Now that we know which registers need to be saved and restored, allocate
+    // stack slots for them.
+    for (std::vector<CalleeSavedInfo>::iterator I = CSI.begin(), E = CSI.end();
+         I != E; ++I) {
+      unsigned Reg = I->getReg();
+      const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
+
+      int FrameIdx;
+      if (RegInfo->hasReservedSpillSlot(F, Reg, FrameIdx)) {
+        I->setFrameIdx(FrameIdx);
+        continue;
+      }
 
-    // Check to see if this physreg must be spilled to a particular stack slot
-    // on this target.
-    const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots;
-    while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
-           FixedSlot->Reg != Reg)
-      ++FixedSlot;
-
-    if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
-      // Nope, just spill it anywhere convenient.
-      unsigned Align = RC->getAlignment();
-      unsigned StackAlign = TFI->getStackAlignment();
-
-      // We may not be able to satisfy the desired alignment specification of
-      // the TargetRegisterClass if the stack alignment is smaller. Use the
-      // min.
-      Align = std::min(Align, StackAlign);
-      FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
+      // Check to see if this physreg must be spilled to a particular stack slot
+      // on this target.
+      const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots;
+      while (FixedSlot != FixedSpillSlots + NumFixedSpillSlots &&
+             FixedSlot->Reg != Reg)
+        ++FixedSlot;
+
+      if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
+        // Nope, just spill it anywhere convenient.
+        unsigned Align = RC->getAlignment();
+        unsigned StackAlign = TFI->getStackAlignment();
+
+        // We may not be able to satisfy the desired alignment specification of
+        // the TargetRegisterClass if the stack alignment is smaller. Use the
+        // min.
+        Align = std::min(Align, StackAlign);
+        FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
       if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
       if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
-    } else {
-      // Spill it to the stack where we must.
-      FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, true);
-    }
+      } else {
+        // Spill it to the stack where we must.
+        FrameIdx =
+            MFI->CreateFixedSpillStackObject(RC->getSize(), FixedSlot->Offset);
+      }
 
-    I->setFrameIdx(FrameIdx);
+      I->setFrameIdx(FrameIdx);
+    }
   }
 
   MFI->setCalleeSavedInfo(CSI);