Merged addProlog and addEpilog on x86.

src/IceTargetLoweringX86BaseImpl.h

Index: src/IceTargetLoweringX86BaseImpl.h
diff --git a/src/IceTargetLoweringX86BaseImpl.h b/src/IceTargetLoweringX86BaseImpl.h
index 2669fcfb837f25e96c8c02ae000fe3548635308c..f8c38b22ab3e205cc00611537545386e396e883e 100644
--- a/src/IceTargetLoweringX86BaseImpl.h
+++ b/src/IceTargetLoweringX86BaseImpl.h
@@ -874,6 +874,275 @@ TargetX86Base<TraitsType>::stackVarToAsmOperand(const Variable *Var) const {
                     AssemblerFixup::NoFixup);
 }
 
+template <typename TraitsType>
+void TargetX86Base<TraitsType>::addProlog(CfgNode *Node) {
+  // Stack frame layout:
+  //
+  // +------------------------+
+  // | 1. return address      |
+  // +------------------------+
+  // | 2. preserved registers |
+  // +------------------------+
+  // | 3. padding             |
+  // +------------------------+
+  // | 4. global spill area   |
+  // +------------------------+
+  // | 5. padding             |
+  // +------------------------+
+  // | 6. local spill area    |
+  // +------------------------+
+  // | 7. padding             |
+  // +------------------------+
+  // | 8. allocas             |
+  // +------------------------+
+  // | 9. padding             |
+  // +------------------------+
+  // | 10. out args           |
+  // +------------------------+ <--- StackPointer
+  //
+  // The following variables record the size in bytes of the given areas:
+  //  * X86_RET_IP_SIZE_BYTES:  area 1
+  //  * PreservedRegsSizeBytes: area 2
+  //  * SpillAreaPaddingBytes:  area 3
+  //  * GlobalsSize:            area 4
+  //  * GlobalsAndSubsequentPaddingSize: areas 4 - 5
+  //  * LocalsSpillAreaSize:    area 6
+  //  * SpillAreaSizeBytes:     areas 3 - 10
+  //  * maxOutArgsSizeBytes():  area 10
+
+  // Determine stack frame offsets for each Variable without a register
+  // assignment. This can be done as one variable per stack slot. Or, do
+  // coalescing by running the register allocator again with an infinite set of
+  // registers (as a side effect, this gives variables a second chance at
+  // physical register assignment).
+  //
+  // A middle ground approach is to leverage sparsity and allocate one block of
+  // space on the frame for globals (variables with multi-block lifetime), and
+  // one block to share for locals (single-block lifetime).
+
+  Context.init(Node);
+  Context.setInsertPoint(Context.getCur());
+
+  llvm::SmallBitVector CalleeSaves =
+      getRegisterSet(RegSet_CalleeSave, RegSet_None);
+  RegsUsed = llvm::SmallBitVector(CalleeSaves.size());
+  VarList SortedSpilledVariables, VariablesLinkedToSpillSlots;
+  size_t GlobalsSize = 0;
+  // If there is a separate locals area, this represents that area. Otherwise
+  // it counts any variable not counted by GlobalsSize.
+  SpillAreaSizeBytes = 0;
+  // If there is a separate locals area, this specifies the alignment for it.
+  uint32_t LocalsSlotsAlignmentBytes = 0;
+  // The entire spill locations area gets aligned to largest natural alignment
+  // of the variables that have a spill slot.
+  uint32_t SpillAreaAlignmentBytes = 0;
+  // A spill slot linked to a variable with a stack slot should reuse that
+  // stack slot.
+  std::function<bool(Variable *)> TargetVarHook =
+      [&VariablesLinkedToSpillSlots](Variable *Var) {
+        if (auto *SpillVar =
+                llvm::dyn_cast<typename Traits::SpillVariable>(Var)) {
+          assert(Var->mustNotHaveReg());
+          if (SpillVar->getLinkedTo() && !SpillVar->getLinkedTo()->hasReg()) {
+            VariablesLinkedToSpillSlots.push_back(Var);
+            return true;
+          }
+        }
+        return false;
+      };
+
+  // Compute the list of spilled variables and bounds for GlobalsSize, etc.
+  getVarStackSlotParams(SortedSpilledVariables, RegsUsed, &GlobalsSize,
+                        &SpillAreaSizeBytes, &SpillAreaAlignmentBytes,
+                        &LocalsSlotsAlignmentBytes, TargetVarHook);
+  uint32_t LocalsSpillAreaSize = SpillAreaSizeBytes;
+  SpillAreaSizeBytes += GlobalsSize;
+
+  // Add push instructions for preserved registers.
+  uint32_t NumCallee = 0;
+  size_t PreservedRegsSizeBytes = 0;
+  llvm::SmallBitVector Pushed(CalleeSaves.size());
+  for (SizeT i = 0; i < CalleeSaves.size(); ++i) {
+    const int32_t Canonical = Traits::getBaseReg(i);
+    assert(Canonical == Traits::getBaseReg(Canonical));
+    if (CalleeSaves[i] && RegsUsed[i]) {
+      Pushed[Canonical] = true;
+    }
+  }
+  for (SizeT i = 0; i < Pushed.size(); ++i) {
+    if (!Pushed[i])
+      continue;
+    assert(static_cast<int32_t>(i) == Traits::getBaseReg(i));
+    ++NumCallee;
+    PreservedRegsSizeBytes += typeWidthInBytes(Traits::WordType);
+    _push_reg(getPhysicalRegister(i, Traits::WordType));
+  }
+  Ctx->statsUpdateRegistersSaved(NumCallee);
+
+  // Generate "push frameptr; mov frameptr, stackptr"
+  if (IsEbpBasedFrame) {
+    assert((RegsUsed & getRegisterSet(RegSet_FramePointer, RegSet_None))
+               .count() == 0);
+    PreservedRegsSizeBytes += typeWidthInBytes(Traits::WordType);
+    _link_bp();
+  }
+
+  // Align the variables area. SpillAreaPaddingBytes is the size of the region
+  // after the preserved registers and before the spill areas.
+  // LocalsSlotsPaddingBytes is the amount of padding between the globals and
+  // locals area if they are separate.
+  assert(SpillAreaAlignmentBytes <= Traits::X86_STACK_ALIGNMENT_BYTES);
+  assert(LocalsSlotsAlignmentBytes <= SpillAreaAlignmentBytes);
+  uint32_t SpillAreaPaddingBytes = 0;
+  uint32_t LocalsSlotsPaddingBytes = 0;
+  alignStackSpillAreas(Traits::X86_RET_IP_SIZE_BYTES + PreservedRegsSizeBytes,
+                       SpillAreaAlignmentBytes, GlobalsSize,
+                       LocalsSlotsAlignmentBytes, &SpillAreaPaddingBytes,
+                       &LocalsSlotsPaddingBytes);
+  SpillAreaSizeBytes += SpillAreaPaddingBytes + LocalsSlotsPaddingBytes;
+  uint32_t GlobalsAndSubsequentPaddingSize =
+      GlobalsSize + LocalsSlotsPaddingBytes;
+
+  // Functions returning scalar floating point types may need to convert values
+  // from an in-register xmm value to the top of the x87 floating point stack.
+  // This is done by a movp[sd] and an fld[sd].  Ensure there is enough scratch
+  // space on the stack for this.
+  const Type ReturnType = Func->getReturnType();
+  if (!Traits::X86_PASS_SCALAR_FP_IN_XMM && isScalarFloatingType(ReturnType)) {

[John, 2016/01/21 15:04:52]

optional: I personally prefer

if (!Traits:BLAH) {
  if (...) {
  }
}

because then I know the nested code is BLAH-specific.

[sehr, 2016/01/21 16:02:10]

Kernighan's "Elements of Programming Style" teaches to avoid deep if-nests when
possible.  But style consistency prevails.  Changed.

+    // Avoid misaligned double-precicion load/store.
+    NeedsStackAlignment = true;
+    SpillAreaSizeBytes =
+        std::max(typeWidthInBytesOnStack(ReturnType), SpillAreaSizeBytes);
+  }
+
+  // Align esp if necessary.
+  if (NeedsStackAlignment) {
+    uint32_t StackOffset =
+        Traits::X86_RET_IP_SIZE_BYTES + PreservedRegsSizeBytes;
+    uint32_t StackSize =
+        Traits::applyStackAlignment(StackOffset + SpillAreaSizeBytes);
+    StackSize = Traits::applyStackAlignment(StackSize + maxOutArgsSizeBytes());
+    SpillAreaSizeBytes = StackSize - StackOffset;
+  } else {
+    SpillAreaSizeBytes += maxOutArgsSizeBytes();
+  }
+
+  // Combine fixed allocations into SpillAreaSizeBytes if we are emitting the
+  // fixed allocations in the prolog.
+  if (PrologEmitsFixedAllocas)
+    SpillAreaSizeBytes += FixedAllocaSizeBytes;
+  if (SpillAreaSizeBytes) {
+    // Generate "sub stackptr, SpillAreaSizeBytes"
+    _sub_sp(Ctx->getConstantInt32(SpillAreaSizeBytes));
+    // If the fixed allocas are aligned more than the stack frame, align the
+    // stack pointer accordingly.
+    if (PrologEmitsFixedAllocas &&
+        FixedAllocaAlignBytes > Traits::X86_STACK_ALIGNMENT_BYTES) {
+      assert(IsEbpBasedFrame);
+      _and(getPhysicalRegister(getStackReg(), Traits::WordType),
+           Ctx->getConstantInt32(-FixedAllocaAlignBytes));
+    }
+  }
+
+  // Account for known-frame-offset alloca instructions that were not already
+  // combined into the prolog.
+  if (!PrologEmitsFixedAllocas)
+    SpillAreaSizeBytes += FixedAllocaSizeBytes;
+
+  Ctx->statsUpdateFrameBytes(SpillAreaSizeBytes);
+
+  // Fill in stack offsets for stack args, and copy args into registers for
+  // those that were register-allocated. Args are pushed right to left, so
+  // Arg[0] is closest to the stack/frame pointer.
+  Variable *FramePtr =
+      getPhysicalRegister(getFrameOrStackReg(), Traits::WordType);
+  size_t BasicFrameOffset =
+      PreservedRegsSizeBytes + Traits::X86_RET_IP_SIZE_BYTES;
+  if (!IsEbpBasedFrame)
+    BasicFrameOffset += SpillAreaSizeBytes;
+
+  emitGetIP(Node);
+
+  const VarList &Args = Func->getArgs();
+  size_t InArgsSizeBytes = 0;
+  unsigned NumXmmArgs = 0;
+  unsigned NumGPRArgs = 0;
+  for (Variable *Arg : Args) {
+    // Skip arguments passed in registers.
+    if (isVectorType(Arg->getType())) {
+      if (Traits::getRegisterForXmmArgNum(NumXmmArgs) != Variable::NoRegister) {
+        ++NumXmmArgs;
+        continue;
+      }
+    } else if (isScalarFloatingType(Arg->getType())) {
+      if (Traits::X86_PASS_SCALAR_FP_IN_XMM &&
+          Traits::getRegisterForXmmArgNum(NumXmmArgs) != Variable::NoRegister) {
+        ++NumXmmArgs;
+        continue;
+      }
+    } else {
+      assert(isScalarIntegerType(Arg->getType()));
+      if (Traits::getRegisterForGprArgNum(Traits::WordType, NumGPRArgs) !=
+          Variable::NoRegister) {
+        ++NumGPRArgs;
+        continue;
+      }
+    }
+    // For esp-based frames where the allocas are done outside the prolog, the
+    // esp value may not stabilize to its home value until after all the
+    // fixed-size alloca instructions have executed.  In this case, a stack
+    // adjustment is needed when accessing in-args in order to copy them into
+    // registers.
+    size_t StackAdjBytes = 0;
+    if (!IsEbpBasedFrame && !PrologEmitsFixedAllocas)
+      StackAdjBytes -= FixedAllocaSizeBytes;
+    finishArgumentLowering(Arg, FramePtr, BasicFrameOffset, StackAdjBytes,
+                           InArgsSizeBytes);
+  }
+
+  // Fill in stack offsets for locals.
+  assignVarStackSlots(SortedSpilledVariables, SpillAreaPaddingBytes,
+                      SpillAreaSizeBytes, GlobalsAndSubsequentPaddingSize,
+                      IsEbpBasedFrame);
+  // Assign stack offsets to variables that have been linked to spilled
+  // variables.
+  for (Variable *Var : VariablesLinkedToSpillSlots) {
+    Variable *Linked =
+        (llvm::cast<typename Traits::SpillVariable>(Var))->getLinkedTo();
+    Var->setStackOffset(Linked->getStackOffset());
+  }
+  this->HasComputedFrame = true;
+
+  if (BuildDefs::dump() && Func->isVerbose(IceV_Frame)) {
+    OstreamLocker L(Func->getContext());
+    Ostream &Str = Func->getContext()->getStrDump();
+
+    Str << "Stack layout:\n";
+    uint32_t EspAdjustmentPaddingSize =
+        SpillAreaSizeBytes - LocalsSpillAreaSize -
+        GlobalsAndSubsequentPaddingSize - SpillAreaPaddingBytes -
+        maxOutArgsSizeBytes();
+    Str << " in-args = " << InArgsSizeBytes << " bytes\n"
+        << " return address = " << Traits::X86_RET_IP_SIZE_BYTES << " bytes\n"
+        << " preserved registers = " << PreservedRegsSizeBytes << " bytes\n"
+        << " spill area padding = " << SpillAreaPaddingBytes << " bytes\n"
+        << " globals spill area = " << GlobalsSize << " bytes\n"
+        << " globals-locals spill areas intermediate padding = "
+        << GlobalsAndSubsequentPaddingSize - GlobalsSize << " bytes\n"
+        << " locals spill area = " << LocalsSpillAreaSize << " bytes\n"
+        << " esp alignment padding = " << EspAdjustmentPaddingSize
+        << " bytes\n";
+
+    Str << "Stack details:\n"
+        << " esp adjustment = " << SpillAreaSizeBytes << " bytes\n"
+        << " spill area alignment = " << SpillAreaAlignmentBytes << " bytes\n"
+        << " outgoing args size = " << maxOutArgsSizeBytes() << " bytes\n"
+        << " locals spill area alignment = " << LocalsSlotsAlignmentBytes
+        << " bytes\n"
+        << " is ebp based = " << IsEbpBasedFrame << "\n";
+  }
+}
+
 /// Helper function for addProlog().
 ///
 /// This assumes Arg is an argument passed on the stack. This sets the frame
@@ -920,6 +1189,63 @@ void TargetX86Base<TraitsType>::finishArgumentLowering(
   }
 }
 
+template <typename TraitsType>
+void TargetX86Base<TraitsType>::addEpilog(CfgNode *Node) {
+  InstList &Insts = Node->getInsts();
+  InstList::reverse_iterator RI, E;
+  for (RI = Insts.rbegin(), E = Insts.rend(); RI != E; ++RI) {
+    if (llvm::isa<typename Traits::Insts::Ret>(*RI))
+      break;
+  }
+  if (RI == E)
+    return;
+
+  // Convert the reverse_iterator position into its corresponding (forward)
+  // iterator position.
+  InstList::iterator InsertPoint = RI.base();
+  --InsertPoint;
+  Context.init(Node);
+  Context.setInsertPoint(InsertPoint);
+
+  if (IsEbpBasedFrame) {
+    _unlink_bp();
+  } else {
+    // add stackptr, SpillAreaSizeBytes
+    if (SpillAreaSizeBytes != 0) {
+      _add_sp(Ctx->getConstantInt32(SpillAreaSizeBytes));
+    }
+  }
+
+  // Add pop instructions for preserved registers.
+  llvm::SmallBitVector CalleeSaves =
+      getRegisterSet(RegSet_CalleeSave, RegSet_None);
+  llvm::SmallBitVector Popped(CalleeSaves.size());
+  for (int32_t i = CalleeSaves.size() - 1; i >= 0; --i) {
+    if (static_cast<SizeT>(i) == getFrameReg() && IsEbpBasedFrame)
+      continue;
+    const SizeT Canonical = Traits::getBaseReg(i);
+    if (CalleeSaves[i] && RegsUsed[i]) {
+      Popped[Canonical] = true;
+    }
+  }
+  for (int32_t i = Popped.size() - 1; i >= 0; --i) {
+    if (!Popped[i])
+      continue;
+    assert(i == Traits::getBaseReg(i));
+    _pop(getPhysicalRegister(i, Traits::WordType));
+  }
+
+  if (!NeedSandboxing) {
+    return;
+  }
+  emitSandboxedReturn();
+  if (RI->getSrcSize()) {
+    auto *RetValue = llvm::cast<Variable>(RI->getSrc(0));
+    Context.insert<InstFakeUse>(RetValue);
+  }
+  RI->setDeleted();
+}
+
 template <typename TraitsType> Type TargetX86Base<TraitsType>::stackSlotType() {
   return Traits::WordType;
 }