Reapply: IR: add optional type to 'byval' function parameters

When we switch to opaque pointer types we will need some way to describe
how many bytes a 'byval' parameter should occupy on the stack. This adds
a (for now) optional extra type parameter.

If present, the type must match the pointee type of the argument.

The original commit did not remap byval types when linking modules, which broke
LTO. This version fixes that.

Note to front-end maintainers: if this causes test failures, it's probably
because the "byval" attribute is printed after attributes without any parameter
after this change.

llvm-svn: 362128

llvm/docs/LangRef.rst

@@ -1017,7 +1017,7 @@ Currently, only the following parameter attributes are defined:
     opposed to memory, though some targets use it to distinguish between
     two different kinds of registers). Use of this attribute is
     target-specific.
-``byval``
+``byval`` or ``byval(<ty>)``
     This indicates that the pointer parameter should really be passed by
     value to the function. The attribute implies that a hidden copy of
     the pointee is made between the caller and the callee, so the callee
@@ -1029,6 +1029,9 @@ Currently, only the following parameter attributes are defined:
     ``byval`` parameters). This is not a valid attribute for return
     values.
 
+    The byval attribute also supports an optional type argument, which must be
+    the same as the pointee type of the argument.
+
     The byval attribute also supports specifying an alignment with the
     align attribute. It indicates the alignment of the stack slot to
     form and the known alignment of the pointer specified to the call

llvm/docs/ReleaseNotes.rst

@@ -67,6 +67,11 @@ Changes to the LLVM IR
   type is now mandatory. Specify `i8* null` to migrate from the obsoleted
   2-field form.
 
+* The ``byval`` attribute can now take a type parameter:
+  ``byval(<ty>)``. If present it must be identical to the argument's
+  pointee type. In the next release we intend to make this parameter
+  mandatory in preparation for opaque pointer types.
+
 Changes to the ARM Backend
 --------------------------
 

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -188,6 +188,7 @@ class TargetLoweringBase {
     bool IsSwiftSelf : 1;
     bool IsSwiftError : 1;
     uint16_t Alignment = 0;
+    Type *ByValType = nullptr;
 
     ArgListEntry()
         : IsSExt(false), IsZExt(false), IsInReg(false), IsSRet(false),

llvm/include/llvm/IR/Argument.h

@@ -78,6 +78,9 @@ class Argument final : public Value {
   /// If this is a byval or inalloca argument, return its alignment.
   unsigned getParamAlignment() const;
 
+  /// If this is a byval argument, return its type.
+  Type *getParamByValType() const;
+
   /// Return true if this argument has the nest attribute.
   bool hasNestAttr() const;
 

llvm/include/llvm/IR/Attributes.h

@@ -90,6 +90,7 @@ class Attribute {
   static Attribute get(LLVMContext &Context, AttrKind Kind, uint64_t Val = 0);
   static Attribute get(LLVMContext &Context, StringRef Kind,
                        StringRef Val = StringRef());
+  static Attribute get(LLVMContext &Context, AttrKind Kind, Type *Ty);
 
   /// Return a uniquified Attribute object that has the specific
   /// alignment set.
@@ -102,6 +103,7 @@ class Attribute {
   static Attribute getWithAllocSizeArgs(LLVMContext &Context,
                                         unsigned ElemSizeArg,
                                         const Optional<unsigned> &NumElemsArg);
+  static Attribute getWithByValType(LLVMContext &Context, Type *Ty);
 
   //===--------------------------------------------------------------------===//
   // Attribute Accessors
@@ -117,6 +119,9 @@ class Attribute {
   /// attribute.
   bool isStringAttribute() const;
 
+  /// Return true if the attribute is a type attribute.
+  bool isTypeAttribute() const;
+
   /// Return true if the attribute is present.
   bool hasAttribute(AttrKind Val) const;
 
@@ -139,6 +144,10 @@ class Attribute {
   /// attribute to be a string attribute.
   StringRef getValueAsString() const;
 
+  /// Return the attribute's value as a Type. This requires the attribute to be
+  /// a type attribute.
+  Type *getValueAsType() const;
+
   /// Returns the alignment field of an attribute as a byte alignment
   /// value.
   unsigned getAlignment() const;
@@ -279,6 +288,7 @@ class AttributeSet {
   unsigned getStackAlignment() const;
   uint64_t getDereferenceableBytes() const;
   uint64_t getDereferenceableOrNullBytes() const;
+  Type *getByValType() const;
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
   std::string getAsString(bool InAttrGrp = false) const;
 
@@ -598,6 +608,9 @@ class AttributeList {
   /// Return the alignment for the specified function parameter.
   unsigned getParamAlignment(unsigned ArgNo) const;
 
+  /// Return the byval type for the specified function parameter.
+  Type *getParamByValType(unsigned ArgNo) const;
+
   /// Get the stack alignment.
   unsigned getStackAlignment(unsigned Index) const;
 
@@ -697,6 +710,7 @@ class AttrBuilder {
   uint64_t DerefBytes = 0;
   uint64_t DerefOrNullBytes = 0;
   uint64_t AllocSizeArgs = 0;
+  Type *ByValType = nullptr;
 
 public:
   AttrBuilder() = default;
@@ -772,6 +786,9 @@ class AttrBuilder {
   /// dereferenceable_or_null attribute exists (zero is returned otherwise).
   uint64_t getDereferenceableOrNullBytes() const { return DerefOrNullBytes; }
 
+  /// Retrieve the byval type.
+  Type *getByValType() const { return ByValType; }
+
   /// Retrieve the allocsize args, if the allocsize attribute exists.  If it
   /// doesn't exist, pair(0, 0) is returned.
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
@@ -796,6 +813,9 @@ class AttrBuilder {
   AttrBuilder &addAllocSizeAttr(unsigned ElemSizeArg,
                                 const Optional<unsigned> &NumElemsArg);
 
+  /// This turns a byval type into the form used internally in Attribute.
+  AttrBuilder &addByValAttr(Type *Ty);
+
   /// Add an allocsize attribute, using the representation returned by
   /// Attribute.getIntValue().
   AttrBuilder &addAllocSizeAttrFromRawRepr(uint64_t RawAllocSizeRepr);

llvm/include/llvm/IR/CallSite.h

@@ -415,6 +415,11 @@ class CallSiteBase {
     CALLSITE_DELEGATE_GETTER(getParamAlignment(ArgNo));
   }
 
+  /// Extract the byval type for a call or parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    CALLSITE_DELEGATE_GETTER(getParamByValType(ArgNo));
+  }
+
   /// Extract the number of dereferenceable bytes for a call or parameter
   /// (0=unknown).
   uint64_t getDereferenceableBytes(unsigned i) const {

llvm/include/llvm/IR/Function.h

@@ -431,6 +431,11 @@ class Function : public GlobalObject, public ilist_node<Function> {
     return AttributeSets.getParamAlignment(ArgNo);
   }
 
+  /// Extract the byval type for a parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    return AttributeSets.getParamByValType(ArgNo);
+  }
+
   /// Extract the number of dereferenceable bytes for a call or
   /// parameter (0=unknown).
   /// @param i AttributeList index, referring to a return value or argument.

llvm/include/llvm/IR/InstrTypes.h

@@ -1560,6 +1560,11 @@ class CallBase : public Instruction {
     return Attrs.getParamAlignment(ArgNo);
   }
 
+  /// Extract the byval type for a call or parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    return Attrs.getParamByValType(ArgNo);
+  }
+
   /// Extract the number of dereferenceable bytes for a call or
   /// parameter (0=unknown).
   uint64_t getDereferenceableBytes(unsigned i) const {

llvm/lib/AsmParser/LLParser.cpp

@@ -1601,7 +1601,13 @@ bool LLParser::ParseOptionalParamAttrs(AttrBuilder &B) {
       B.addAlignmentAttr(Alignment);
       continue;
     }
-    case lltok::kw_byval:           B.addAttribute(Attribute::ByVal); break;
+    case lltok::kw_byval: {
+      Type *Ty;
+      if (ParseByValWithOptionalType(Ty))
+        return true;
+      B.addByValAttr(Ty);
+      continue;
+    }
     case lltok::kw_dereferenceable: {
       uint64_t Bytes;
       if (ParseOptionalDerefAttrBytes(lltok::kw_dereferenceable, Bytes))
@@ -2454,6 +2460,22 @@ bool LLParser::ParseParameterList(SmallVectorImpl<ParamInfo> &ArgList,
   return false;
 }
 
+/// ParseByValWithOptionalType
+///   ::= byval
+///   ::= byval(<ty>)
+bool LLParser::ParseByValWithOptionalType(Type *&Result) {
+  Result = nullptr;
+  if (!EatIfPresent(lltok::kw_byval))
+    return true;
+  if (!EatIfPresent(lltok::lparen))
+    return false;
+  if (ParseType(Result))
+    return true;
+  if (!EatIfPresent(lltok::rparen))
+    return Error(Lex.getLoc(), "expected ')'");
+  return false;
+}
+
 /// ParseOptionalOperandBundles
 ///    ::= /*empty*/
 ///    ::= '[' OperandBundle [, OperandBundle ]* ']'

llvm/lib/AsmParser/LLParser.h

@@ -339,6 +339,7 @@ namespace llvm {
     bool ParseFnAttributeValuePairs(AttrBuilder &B,
                                     std::vector<unsigned> &FwdRefAttrGrps,
                                     bool inAttrGrp, LocTy &BuiltinLoc);
+    bool ParseByValWithOptionalType(Type *&Result);
 
     // Module Summary Index Parsing.
     bool SkipModuleSummaryEntry();

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -638,6 +638,10 @@ class BitcodeReader : public BitcodeReaderBase, public GVMaterializer {
     return getFnValueByID(ValNo, Ty);
   }
 
+  /// Upgrades old-style typeless byval attributes by adding the corresponding
+  /// argument's pointee type.
+  void propagateByValTypes(CallBase *CB);
+
   /// Converts alignment exponent (i.e. power of two (or zero)) to the
   /// corresponding alignment to use. If alignment is too large, returns
   /// a corresponding error code.
@@ -1492,6 +1496,12 @@ Error BitcodeReader::parseAttributeGroupBlock() {
           if (Error Err = parseAttrKind(Record[++i], &Kind))
             return Err;
 
+          // Upgrade old-style byval attribute to one with a type, even if it's
+          // nullptr. We will have to insert the real type when we associate
+          // this AttributeList with a function.
+          if (Kind == Attribute::ByVal)
+            B.addByValAttr(nullptr);
+
           B.addAttribute(Kind);
         } else if (Record[i] == 1) { // Integer attribute
           Attribute::AttrKind Kind;
@@ -1507,9 +1517,7 @@ Error BitcodeReader::parseAttributeGroupBlock() {
             B.addDereferenceableOrNullAttr(Record[++i]);
           else if (Kind == Attribute::AllocSize)
             B.addAllocSizeAttrFromRawRepr(Record[++i]);
-        } else {                     // String attribute
-          assert((Record[i] == 3 || Record[i] == 4) &&
-                 "Invalid attribute group entry");
+        } else if (Record[i] == 3 || Record[i] == 4) { // String attribute
           bool HasValue = (Record[i++] == 4);
           SmallString<64> KindStr;
           SmallString<64> ValStr;
@@ -1527,6 +1535,15 @@ Error BitcodeReader::parseAttributeGroupBlock() {
           }
 
           B.addAttribute(KindStr.str(), ValStr.str());
+        } else {
+          assert((Record[i] == 5 || Record[i] == 6) &&
+                 "Invalid attribute group entry");
+          bool HasType = Record[i] == 6;
+          Attribute::AttrKind Kind;
+          if (Error Err = parseAttrKind(Record[++i], &Kind))
+            return Err;
+          if (Kind == Attribute::ByVal)
+            B.addByValAttr(HasType ? getTypeByID(Record[++i]) : nullptr);
         }
       }
 
@@ -3028,6 +3045,17 @@ Error BitcodeReader::parseFunctionRecord(ArrayRef<uint64_t> Record) {
   Func->setLinkage(getDecodedLinkage(RawLinkage));
   Func->setAttributes(getAttributes(Record[4]));
 
+  // Upgrade any old-style byval without a type by propagating the argument's
+  // pointee type. There should be no opaque pointers where the byval type is
+  // implicit.
+  for (auto &Arg : Func->args()) {
+    if (Arg.hasByValAttr() && !Arg.getParamByValType()) {
+      Arg.removeAttr(Attribute::ByVal);
+      Arg.addAttr(Attribute::getWithByValType(
+          Context, Arg.getType()->getPointerElementType()));
+    }
+  }
+
   unsigned Alignment;
   if (Error Err = parseAlignmentValue(Record[5], Alignment))
     return Err;
@@ -3441,6 +3469,19 @@ Error BitcodeReader::typeCheckLoadStoreInst(Type *ValType, Type *PtrType) {
   return Error::success();
 }
 
+void BitcodeReader::propagateByValTypes(CallBase *CB) {
+  for (unsigned i = 0; i < CB->getNumArgOperands(); ++i) {
+    if (CB->paramHasAttr(i, Attribute::ByVal) &&
+        !CB->getAttribute(i, Attribute::ByVal).getValueAsType()) {
+      CB->removeParamAttr(i, Attribute::ByVal);
+      CB->addParamAttr(
+          i, Attribute::getWithByValType(
+                 Context,
+                 CB->getArgOperand(i)->getType()->getPointerElementType()));
+    }
+  }
+}
+
 /// Lazily parse the specified function body block.
 Error BitcodeReader::parseFunctionBody(Function *F) {
   if (Stream.EnterSubBlock(bitc::FUNCTION_BLOCK_ID))
@@ -4256,6 +4297,8 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
       cast<InvokeInst>(I)->setCallingConv(
           static_cast<CallingConv::ID>(CallingConv::MaxID & CCInfo));
       cast<InvokeInst>(I)->setAttributes(PAL);
+      propagateByValTypes(cast<CallBase>(I));
+
       break;
     }
     case bitc::FUNC_CODE_INST_RESUME: { // RESUME: [opval]
@@ -4731,6 +4774,7 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
         TCK = CallInst::TCK_NoTail;
       cast<CallInst>(I)->setTailCallKind(TCK);
       cast<CallInst>(I)->setAttributes(PAL);
+      propagateByValTypes(cast<CallBase>(I));
       if (FMF.any()) {
         if (!isa<FPMathOperator>(I))
           return error("Fast-math-flags specified for call without "

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -747,7 +747,7 @@ void ModuleBitcodeWriter::writeAttributeGroupTable() {
         Record.push_back(1);
         Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
         Record.push_back(Attr.getValueAsInt());
-      } else {
+      } else if (Attr.isStringAttribute()) {
         StringRef Kind = Attr.getKindAsString();
         StringRef Val = Attr.getValueAsString();
 
@@ -758,6 +758,13 @@ void ModuleBitcodeWriter::writeAttributeGroupTable() {
           Record.append(Val.begin(), Val.end());
           Record.push_back(0);
         }
+      } else {
+        assert(Attr.isTypeAttribute());
+        Type *Ty = Attr.getValueAsType();
+        Record.push_back(Ty ? 6 : 5);
+        Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
+        if (Ty)
+          Record.push_back(VE.getTypeID(Attr.getValueAsType()));
       }
     }
 
@@ -4126,15 +4133,15 @@ void ModuleBitcodeWriter::write() {
   // Emit blockinfo, which defines the standard abbreviations etc.
   writeBlockInfo();
 
+  // Emit information describing all of the types in the module.
+  writeTypeTable();
+
   // Emit information about attribute groups.
   writeAttributeGroupTable();
 
   // Emit information about parameter attributes.
   writeAttributeTable();
 
-  // Emit information describing all of the types in the module.
-  writeTypeTable();
-
   writeComdats();
 
   // Emit top-level description of module, including target triple, inline asm,

llvm/lib/Bitcode/Writer/ValueEnumerator.cpp

@@ -949,9 +949,11 @@ void ValueEnumerator::incorporateFunction(const Function &F) {
   incorporateFunctionMetadata(F);
 
   // Adding function arguments to the value table.
-  for (const auto &I : F.args())
+  for (const auto &I : F.args()) {
     EnumerateValue(&I);
-
+    if (I.hasAttribute(Attribute::ByVal) && I.getParamByValType())
+      EnumerateType(I.getParamByValType());
+  }
   FirstFuncConstantID = Values.size();
 
   // Add all function-level constants to the value table.

llvm/lib/CodeGen/GlobalISel/CallLowering.cpp

@@ -87,7 +87,10 @@ void CallLowering::setArgFlags(CallLowering::ArgInfo &Arg, unsigned OpIdx,
 
   if (Arg.Flags.isByVal() || Arg.Flags.isInAlloca()) {
     Type *ElementTy = cast<PointerType>(Arg.Ty)->getElementType();
-    Arg.Flags.setByValSize(DL.getTypeAllocSize(ElementTy));
+
+    auto Ty = Attrs.getAttribute(OpIdx, Attribute::ByVal).getValueAsType();
+    Arg.Flags.setByValSize(DL.getTypeAllocSize(Ty ? Ty : ElementTy));
+
     // For ByVal, alignment should be passed from FE.  BE will guess if
     // this info is not there but there are cases it cannot get right.
     unsigned FrameAlign;