X86: Make @llvm.frameaddress work correctly with Windows unwind codes

Simply loading or storing the frame pointer is not sufficient for
Windows targets.  Instead, create a synthetic frame object that we will
lower later.  References to this synthetic object will be replaced with
the correct reference to the frame address.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228748 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86FrameLowering.cpp

@@ -1242,6 +1242,9 @@ int X86FrameLowering::getFrameIndexOffset(const MachineFunction &MF,
       NumBytes = FrameSize - CSSize;
     }
     uint64_t SEHFrameOffset = calculateSetFPREG(NumBytes);
+    if (FI && FI == X86FI->getFAIndex())
+      return -SEHFrameOffset;
+
     // FPDelta is the offset from the "traditional" FP location of the old base
     // pointer followed by return address and the location required by the
     // restricted Win64 prologue.

lib/Target/X86/X86ISelLowering.cpp

@@ -17953,15 +17953,33 @@ SDValue X86TargetLowering::LowerRETURNADDR(SDValue Op,
 }
 
 SDValue X86TargetLowering::LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const {
-  MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
+  MachineFunction &MF = DAG.getMachineFunction();
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
+  const X86RegisterInfo *RegInfo = Subtarget->getRegisterInfo();
+  EVT VT = Op.getValueType();
+
   MFI->setFrameAddressIsTaken(true);
 
-  EVT VT = Op.getValueType();
+  if (MF.getTarget().getMCAsmInfo()->usesWindowsCFI()) {
+    // Depth > 0 makes no sense on targets which use Windows unwind codes.  It
+    // is not possible to crawl up the stack without looking at the unwind codes
+    // simultaneously.
+    int FrameAddrIndex = FuncInfo->getFAIndex();
+    if (!FrameAddrIndex) {
+      // Set up a frame object for the return address.
+      unsigned SlotSize = RegInfo->getSlotSize();
+      FrameAddrIndex = MF.getFrameInfo()->CreateFixedObject(
+          SlotSize, /*Offset=*/INT64_MIN, /*IsImmutable=*/false);
+      FuncInfo->setFAIndex(FrameAddrIndex);
+    }
+    return DAG.getFrameIndex(FrameAddrIndex, VT);
+  }
+
+  unsigned FrameReg =
+      RegInfo->getPtrSizedFrameRegister(DAG.getMachineFunction());
   SDLoc dl(Op);  // FIXME probably not meaningful
   unsigned Depth = cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
-  const X86RegisterInfo *RegInfo = Subtarget->getRegisterInfo();
-  unsigned FrameReg = RegInfo->getPtrSizedFrameRegister(
-      DAG.getMachineFunction());
   assert(((FrameReg == X86::RBP && VT == MVT::i64) ||
           (FrameReg == X86::EBP && VT == MVT::i32)) &&
          "Invalid Frame Register!");

lib/Target/X86/X86MachineFunctionInfo.h

@@ -50,6 +50,9 @@ class X86MachineFunctionInfo : public MachineFunctionInfo {
   /// ReturnAddrIndex - FrameIndex for return slot.
   int ReturnAddrIndex;
 
+  /// \brief FrameIndex for return slot.
+  int FrameAddrIndex;
+
   /// TailCallReturnAddrDelta - The number of bytes by which return address
   /// stack slot is moved as the result of tail call optimization.
   int TailCallReturnAddrDelta;
@@ -92,6 +95,7 @@ public:
                              CalleeSavedFrameSize(0),
                              BytesToPopOnReturn(0),
                              ReturnAddrIndex(0),
+                             FrameAddrIndex(0),
                              TailCallReturnAddrDelta(0),
                              SRetReturnReg(0),
                              GlobalBaseReg(0),
@@ -109,6 +113,7 @@ public:
       CalleeSavedFrameSize(0),
       BytesToPopOnReturn(0),
       ReturnAddrIndex(0),
+      FrameAddrIndex(0),
       TailCallReturnAddrDelta(0),
       SRetReturnReg(0),
       GlobalBaseReg(0),
@@ -139,6 +144,9 @@ public:
   int getRAIndex() const { return ReturnAddrIndex; }
   void setRAIndex(int Index) { ReturnAddrIndex = Index; }
 
+  int getFAIndex() const { return FrameAddrIndex; }
+  void setFAIndex(int Index) { FrameAddrIndex = Index; }
+
   int getTCReturnAddrDelta() const { return TailCallReturnAddrDelta; }
   void setTCReturnAddrDelta(int delta) {TailCallReturnAddrDelta = delta;}
 

test/CodeGen/X86/frameallocate.ll

@@ -32,8 +32,12 @@ define void @alloc_func(i32* %s, i32* %d) {
 }
 
 ; CHECK-LABEL: alloc_func:
+; CHECK: subq    $48, %rsp
+; CHECK: .seh_stackalloc 48
+; CHECK: leaq    48(%rsp), %rbp
+; CHECK: .seh_setframe 5, 48
 ; CHECK: .Lframeallocation_alloc_func = -[[offs:[0-9]+]]
 ; CHECK: movl $42, -[[offs]](%rbp)
-; CHECK: movq %rbp, %rcx
+; CHECK: leaq    -48(%rbp), %rcx
 ; CHECK: callq print_framealloc_from_fp
 ; CHECK: retq