1 files changed, 38 insertions, 36 deletions

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 028c79f3ab6d2..d99065b1b67a0 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -825,41 +825,25 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
       OS << Name << ":";
   }
   OS << V->getName();
-
-  const DIExpression *Expr = MI->getDebugExpression();
-  auto Fragment = Expr->getFragmentInfo();
-  if (Fragment)
-    OS << " [fragment offset=" << Fragment->OffsetInBits
-       << " size=" << Fragment->SizeInBits << "]";
   OS << " <- ";
 
   // The second operand is only an offset if it's an immediate.
-  bool Deref = false;
   bool MemLoc = MI->getOperand(0).isReg() && MI->getOperand(1).isImm();
   int64_t Offset = MemLoc ? MI->getOperand(1).getImm() : 0;
-  for (unsigned i = 0; i < Expr->getNumElements(); ++i) {
-    uint64_t Op = Expr->getElement(i);
-    if (Op == dwarf::DW_OP_LLVM_fragment) {
-      // There can't be any operands after this in a valid expression
-      break;
-    } else if (Deref) {
-      // We currently don't support extra Offsets or derefs after the first
-      // one. Bail out early instead of emitting an incorrect comment.
-      OS << " [complex expression]";
-      AP.OutStreamer->emitRawComment(OS.str());
-      return true;
-    } else if (Op == dwarf::DW_OP_deref) {
-      Deref = true;
-      continue;
-    }
-
-    uint64_t ExtraOffset = Expr->getElement(i++);
-    if (Op == dwarf::DW_OP_plus)
-      Offset += ExtraOffset;
-    else {
-      assert(Op == dwarf::DW_OP_minus);
-      Offset -= ExtraOffset;
+  const DIExpression *Expr = MI->getDebugExpression();
+  if (Expr->getNumElements()) {
+    OS << '[';
+    bool NeedSep = false;
+    for (auto Op : Expr->expr_ops()) {
+      if (NeedSep)
+        OS << ", ";
+      else
+        NeedSep = true;
+      OS << dwarf::OperationEncodingString(Op.getOp());
+      for (unsigned I = 0; I < Op.getNumArgs(); ++I)
+        OS << ' ' << Op.getArg(I);
     }
+    OS << "] ";
   }
 
   // Register or immediate value. Register 0 means undef.
@@ -890,7 +874,7 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
       const TargetFrameLowering *TFI = AP.MF->getSubtarget().getFrameLowering();
       Offset += TFI->getFrameIndexReference(*AP.MF,
                                             MI->getOperand(0).getIndex(), Reg);
-      Deref = true;
+      MemLoc = true;
     }
     if (Reg == 0) {
       // Suppress offset, it is not meaningful here.
@@ -899,12 +883,12 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
       AP.OutStreamer->emitRawComment(OS.str());
       return true;
     }
-    if (MemLoc || Deref)
+    if (MemLoc)
       OS << '[';
     OS << PrintReg(Reg, AP.MF->getSubtarget().getRegisterInfo());
   }
 
-  if (MemLoc || Deref)
+  if (MemLoc)
     OS << '+' << Offset << ']';
 
   // NOTE: Want this comment at start of line, don't emit with AddComment.
@@ -936,6 +920,16 @@ void AsmPrinter::emitCFIInstruction(const MachineInstr &MI) {
   if (needsCFIMoves() == CFI_M_None)
     return;
 
+  // If there is no "real" instruction following this CFI instruction, skip
+  // emitting it; it would be beyond the end of the function's FDE range.
+  auto *MBB = MI.getParent();
+  auto I = std::next(MI.getIterator());
+  while (I != MBB->end() && I->isTransient())
+    ++I;
+  if (I == MBB->instr_end() &&
+      MBB->getReverseIterator() == MBB->getParent()->rbegin())
+    return;
+
   const std::vector<MCCFIInstruction> &Instrs = MF->getFrameInstructions();
   unsigned CFIIndex = MI.getOperand(0).getCFIIndex();
   const MCCFIInstruction &CFI = Instrs[CFIIndex];
@@ -1046,15 +1040,23 @@ void AsmPrinter::EmitFunctionBody() {
   // If the function is empty and the object file uses .subsections_via_symbols,
   // then we need to emit *something* to the function body to prevent the
   // labels from collapsing together.  Just emit a noop.
-  if ((MAI->hasSubsectionsViaSymbols() && !HasAnyRealCode)) {
+  // Similarly, don't emit empty functions on Windows either. It can lead to
+  // duplicate entries (two functions with the same RVA) in the Guard CF Table
+  // after linking, causing the kernel not to load the binary:
+  // https://developercommunity.visualstudio.com/content/problem/45366/vc-linker-creates-invalid-dll-with-clang-cl.html
+  // FIXME: Hide this behind some API in e.g. MCAsmInfo or MCTargetStreamer.
+  const Triple &TT = TM.getTargetTriple();
+  if (!HasAnyRealCode && (MAI->hasSubsectionsViaSymbols() ||
+                          (TT.isOSWindows() && TT.isOSBinFormatCOFF()))) {
     MCInst Noop;
-    MF->getSubtarget().getInstrInfo()->getNoopForMachoTarget(Noop);
-    OutStreamer->AddComment("avoids zero-length function");
+    MF->getSubtarget().getInstrInfo()->getNoop(Noop);
 
     // Targets can opt-out of emitting the noop here by leaving the opcode
     // unspecified.
-    if (Noop.getOpcode())
+    if (Noop.getOpcode()) {
+      OutStreamer->AddComment("avoids zero-length function");
       OutStreamer->EmitInstruction(Noop, getSubtargetInfo());
+    }
   }
 
   const Function *F = MF->getFunction();