AArch64: Safely handle the incoming sret call argument.

This adds a safe interface to the machine independent InputArg struct
for accessing the index of the original (IR-level) argument. When a
non-native return type is lowered, we generate the hidden
machine-level sret argument on-the-fly. Before this fix, we were
representing this argument as OrigArgIndex == 0, which is an outright
lie. In particular this crashed in the AArch64 backend where we
actually try to access the type of the original argument.

Now we use a sentinel value for machine arguments that have no
original argument index. AArch64, ARM, Mips, and PPC now check for this
case before accessing the original argument.

Fixes <rdar://19792160> Null pointer assertion in AArch64TargetLowering

llvm-svn: 229413

include/llvm/Target/TargetCallingConv.h

@@ -134,6 +134,8 @@ namespace ISD {
 
     /// Index original Function's argument.
     unsigned OrigArgIndex;
+    /// Sentinel value for implicit machine-level input arguments.
+    static const unsigned NoArgIndex = UINT_MAX;
 
     /// Offset in bytes of current input value relative to the beginning of
     /// original argument. E.g. if argument was splitted into four 32 bit
@@ -147,6 +149,15 @@ namespace ISD {
       VT = vt.getSimpleVT();
       ArgVT = argvt;
     }
+
+    bool isOrigArg() const {
+      return OrigArgIndex != NoArgIndex;
+    }
+
+    unsigned getOrigArgIndex() const {
+      assert(OrigArgIndex != NoArgIndex && "Implicit machine-level argument");
+      return OrigArgIndex;
+    }
   };
 
   /// OutputArg - This struct carries flags and a value for a

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -7673,7 +7673,8 @@ void SelectionDAGISel::LowerArguments(const Function &F) {
     ISD::ArgFlagsTy Flags;
     Flags.setSRet();
     MVT RegisterVT = TLI->getRegisterType(*DAG.getContext(), ValueVTs[0]);
-    ISD::InputArg RetArg(Flags, RegisterVT, ValueVTs[0], true, 0, 0);
+    ISD::InputArg RetArg(Flags, RegisterVT, ValueVTs[0], true,
+                         ISD::InputArg::NoArgIndex, 0);
     Ins.push_back(RetArg);
   }
 

lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -2021,18 +2021,19 @@ SDValue AArch64TargetLowering::LowerFormalArguments(
   unsigned CurArgIdx = 0;
   for (unsigned i = 0; i != NumArgs; ++i) {
     MVT ValVT = Ins[i].VT;
-    std::advance(CurOrigArg, Ins[i].OrigArgIndex - CurArgIdx);
-    CurArgIdx = Ins[i].OrigArgIndex;
-
-    // Get type of the original argument.
-    EVT ActualVT = getValueType(CurOrigArg->getType(), /*AllowUnknown*/ true);
-    MVT ActualMVT = ActualVT.isSimple() ? ActualVT.getSimpleVT() : MVT::Other;
-    // If ActualMVT is i1/i8/i16, we should set LocVT to i8/i8/i16.
-    if (ActualMVT == MVT::i1 || ActualMVT == MVT::i8)
-      ValVT = MVT::i8;
-    else if (ActualMVT == MVT::i16)
-      ValVT = MVT::i16;
+    if (Ins[i].isOrigArg()) {
+      std::advance(CurOrigArg, Ins[i].getOrigArgIndex() - CurArgIdx);
+      CurArgIdx = Ins[i].getOrigArgIndex();
 
+      // Get type of the original argument.
+      EVT ActualVT = getValueType(CurOrigArg->getType(), /*AllowUnknown*/ true);
+      MVT ActualMVT = ActualVT.isSimple() ? ActualVT.getSimpleVT() : MVT::Other;
+      // If ActualMVT is i1/i8/i16, we should set LocVT to i8/i8/i16.
+      if (ActualMVT == MVT::i1 || ActualMVT == MVT::i8)
+        ValVT = MVT::i8;
+      else if (ActualMVT == MVT::i16)
+        ValVT = MVT::i16;
+    }
     CCAssignFn *AssignFn = CCAssignFnForCall(CallConv, /*IsVarArg=*/false);
     bool Res =
         AssignFn(i, ValVT, ValVT, CCValAssign::Full, Ins[i].Flags, CCInfo);

lib/Target/ARM/ARMISelLowering.cpp

@@ -3084,8 +3084,11 @@ ARMTargetLowering::LowerFormalArguments(SDValue Chain,
 
   for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
     CCValAssign &VA = ArgLocs[i];
-    std::advance(CurOrigArg, Ins[VA.getValNo()].OrigArgIndex - CurArgIdx);
-    CurArgIdx = Ins[VA.getValNo()].OrigArgIndex;
+    if (Ins[VA.getValNo()].isOrigArg()) {
+      std::advance(CurOrigArg,
+                   Ins[VA.getValNo()].getOrigArgIndex() - CurArgIdx);
+      CurArgIdx = Ins[VA.getValNo()].getOrigArgIndex();
+    }
     // Arguments stored in registers.
     if (VA.isRegLoc()) {
       EVT RegVT = VA.getLocVT();
@@ -3165,7 +3168,7 @@ ARMTargetLowering::LowerFormalArguments(SDValue Chain,
       assert(VA.isMemLoc());
       assert(VA.getValVT() != MVT::i64 && "i64 should already be lowered");
 
-      int index = ArgLocs[i].getValNo();
+      int index = VA.getValNo();
 
       // Some Ins[] entries become multiple ArgLoc[] entries.
       // Process them only once.
@@ -3178,6 +3181,8 @@ ARMTargetLowering::LowerFormalArguments(SDValue Chain,
           // Since they could be overwritten by lowering of arguments in case of
           // a tail call.
           if (Flags.isByVal()) {
+            assert(Ins[index].isOrigArg() &&
+                   "Byval arguments cannot be implicit");
             unsigned CurByValIndex = CCInfo.getInRegsParamsProcessed();
 
             ByValStoreOffset = RoundUpToAlignment(ByValStoreOffset, Flags.getByValAlign());

lib/Target/Mips/MipsCCState.cpp

@@ -132,8 +132,8 @@ void MipsCCState::PreAnalyzeFormalArgumentsForF128(
       continue;
     }
 
-    assert(Ins[i].OrigArgIndex < MF.getFunction()->arg_size());
-    std::advance(FuncArg, Ins[i].OrigArgIndex);
+    assert(Ins[i].getOrigArgIndex() < MF.getFunction()->arg_size());
+    std::advance(FuncArg, Ins[i].getOrigArgIndex());
 
     OriginalArgWasF128.push_back(
         originalTypeIsF128(FuncArg->getType(), nullptr));

lib/Target/Mips/MipsISelLowering.cpp

@@ -2873,13 +2873,16 @@ MipsTargetLowering::LowerFormalArguments(SDValue Chain,
 
   for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
     CCValAssign &VA = ArgLocs[i];
-    std::advance(FuncArg, Ins[i].OrigArgIndex - CurArgIdx);
-    CurArgIdx = Ins[i].OrigArgIndex;
+    if (Ins[i].isOrigArg()) {
+      std::advance(FuncArg, Ins[i].getOrigArgIndex() - CurArgIdx);
+      CurArgIdx = Ins[i].getOrigArgIndex();
+    }
     EVT ValVT = VA.getValVT();
     ISD::ArgFlagsTy Flags = Ins[i].Flags;
     bool IsRegLoc = VA.isRegLoc();
 
     if (Flags.isByVal()) {
+      assert(Ins[i].isOrigArg() && "Byval arguments cannot be implicit");
       unsigned FirstByValReg, LastByValReg;
       unsigned ByValIdx = CCInfo.getInRegsParamsProcessed();
       CCInfo.getInRegsParamInfo(ByValIdx, FirstByValReg, LastByValReg);

lib/Target/PowerPC/PPCISelLowering.cpp

@@ -2698,9 +2698,10 @@ PPCTargetLowering::LowerFormalArguments_64SVR4(
     unsigned ObjSize = ObjectVT.getStoreSize();
     unsigned ArgSize = ObjSize;
     ISD::ArgFlagsTy Flags = Ins[ArgNo].Flags;
-    std::advance(FuncArg, Ins[ArgNo].OrigArgIndex - CurArgIdx);
-    CurArgIdx = Ins[ArgNo].OrigArgIndex;
-
+    if (Ins[ArgNo].isOrigArg()) {
+      std::advance(FuncArg, Ins[ArgNo].getOrigArgIndex() - CurArgIdx);
+      CurArgIdx = Ins[ArgNo].getOrigArgIndex();
+    }
     // We re-align the argument offset for each argument, except when using the
     // fast calling convention, when we need to make sure we do that only when
     // we'll actually use a stack slot.
@@ -2723,6 +2724,8 @@ PPCTargetLowering::LowerFormalArguments_64SVR4(
     // FIXME the codegen can be much improved in some cases.
     // We do not have to keep everything in memory.
     if (Flags.isByVal()) {
+      assert(Ins[ArgNo].isOrigArg() && "Byval arguments cannot be implicit");
+
       if (CallConv == CallingConv::Fast)
         ComputeArgOffset();
 
@@ -3101,9 +3104,10 @@ PPCTargetLowering::LowerFormalArguments_Darwin(
     unsigned ObjSize = ObjectVT.getSizeInBits()/8;
     unsigned ArgSize = ObjSize;
     ISD::ArgFlagsTy Flags = Ins[ArgNo].Flags;
-    std::advance(FuncArg, Ins[ArgNo].OrigArgIndex - CurArgIdx);
-    CurArgIdx = Ins[ArgNo].OrigArgIndex;
-
+    if (Ins[ArgNo].isOrigArg()) {
+      std::advance(FuncArg, Ins[ArgNo].getOrigArgIndex() - CurArgIdx);
+      CurArgIdx = Ins[ArgNo].getOrigArgIndex();
+    }
     unsigned CurArgOffset = ArgOffset;
 
     // Varargs or 64 bit Altivec parameters are padded to a 16 byte boundary.
@@ -3124,6 +3128,8 @@ PPCTargetLowering::LowerFormalArguments_Darwin(
     // FIXME the codegen can be much improved in some cases.
     // We do not have to keep everything in memory.
     if (Flags.isByVal()) {
+      assert(Ins[ArgNo].isOrigArg() && "Byval arguments cannot be implicit");
+
       // ObjSize is the true size, ArgSize rounded up to multiple of registers.
       ObjSize = Flags.getByValSize();
       ArgSize = ((ObjSize + PtrByteSize - 1)/PtrByteSize) * PtrByteSize;

lib/Target/R600/R600ISelLowering.cpp

@@ -1693,7 +1693,7 @@ SDValue R600TargetLowering::LowerFormalArguments(
     // XXX - I think PartOffset should give you this, but it seems to give the
     // size of the register which isn't useful.
 
-    unsigned ValBase = ArgLocs[In.OrigArgIndex].getLocMemOffset();
+    unsigned ValBase = ArgLocs[In.getOrigArgIndex()].getLocMemOffset();
     unsigned PartOffset = VA.getLocMemOffset();
     unsigned Offset = 36 + VA.getLocMemOffset();
 

lib/Target/R600/SIISelLowering.cpp

@@ -446,7 +446,7 @@ SDValue SITargetLowering::LowerFormalArguments(
       // We REALLY want the ORIGINAL number of vertex elements here, e.g. a
       // three or five element vertex only needs three or five registers,
       // NOT four or eigth.
-      Type *ParamType = FType->getParamType(Arg.OrigArgIndex);
+      Type *ParamType = FType->getParamType(Arg.getOrigArgIndex());
       unsigned NumElements = ParamType->getVectorNumElements();
 
       for (unsigned j = 0; j != NumElements; ++j) {
@@ -529,7 +529,7 @@ SDValue SITargetLowering::LowerFormalArguments(
                                    Offset, Ins[i].Flags.isSExt());
 
       const PointerType *ParamTy =
-          dyn_cast<PointerType>(FType->getParamType(Ins[i].OrigArgIndex));
+        dyn_cast<PointerType>(FType->getParamType(Ins[i].getOrigArgIndex()));
       if (Subtarget->getGeneration() == AMDGPUSubtarget::SOUTHERN_ISLANDS &&
           ParamTy && ParamTy->getAddressSpace() == AMDGPUAS::LOCAL_ADDRESS) {
         // On SI local pointers are just offsets into LDS, so they are always
@@ -564,7 +564,7 @@ SDValue SITargetLowering::LowerFormalArguments(
     if (Arg.VT.isVector()) {
 
       // Build a vector from the registers
-      Type *ParamType = FType->getParamType(Arg.OrigArgIndex);
+      Type *ParamType = FType->getParamType(Arg.getOrigArgIndex());
       unsigned NumElements = ParamType->getVectorNumElements();
 
       SmallVector<SDValue, 4> Regs;

test/CodeGen/AArch64/implicit-sret.ll

@@ -0,0 +1,13 @@
+; RUN: llc %s -o - -mtriple=arm64-apple-ios7.0 | FileCheck %s
+;
+; Handle implicit sret arguments that are generated on-the-fly during lowering.
+; <rdar://19792160> Null pointer assertion in AArch64TargetLowering
+
+; CHECK-LABEL: big_retval
+; ... str or stp for the first 1024 bits
+; CHECK: strb wzr, [x8, #128]
+; CHECK: ret
+define i1032 @big_retval() {
+entry:
+  ret i1032 0
+}