[Attributes] Return Optional from getAllocSizeArgs() (NFC)

As suggested on D135572, return Optional<> from getAllocSizeArgs()
rather than the peculiar pair(0, 0) sentinel.

The method on Attribute itself does not return Optional, because
the attribute must exist in that case.

Author: nikic

llvm/include/llvm/IR/Attributes.h

@@ -227,8 +227,7 @@ class Attribute {
   /// dereferenceable_or_null attribute.
   uint64_t getDereferenceableOrNullBytes() const;
 
-  /// Returns the argument numbers for the allocsize attribute (or pair(0, 0)
-  /// if not known).
+  /// Returns the argument numbers for the allocsize attribute.
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
 
   /// Returns the minimum value for the vscale_range attribute.
@@ -371,7 +370,7 @@ class AttributeSet {
   Type *getPreallocatedType() const;
   Type *getInAllocaType() const;
   Type *getElementType() const;
-  std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
+  Optional<std::pair<unsigned, Optional<unsigned>>> getAllocSizeArgs() const;
   unsigned getVScaleRangeMin() const;
   Optional<unsigned> getVScaleRangeMax() const;
   UWTableKind getUWTableKind() const;
@@ -1142,9 +1141,8 @@ class AttrBuilder {
   /// Retrieve the inalloca type.
   Type *getInAllocaType() const { return getTypeAttr(Attribute::InAlloca); }
 
-  /// 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;
+  /// Retrieve the allocsize args, or None if the attribute does not exist.
+  Optional<std::pair<unsigned, Optional<unsigned>>> getAllocSizeArgs() const;
 
   /// Add integer attribute with raw value (packed/encoded if necessary).
   AttrBuilder &addRawIntAttr(Attribute::AttrKind Kind, uint64_t Value);

llvm/lib/IR/AttributeImpl.h

@@ -258,7 +258,7 @@ class AttributeSetNode final
   MaybeAlign getStackAlignment() const;
   uint64_t getDereferenceableBytes() const;
   uint64_t getDereferenceableOrNullBytes() const;
-  std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
+  Optional<std::pair<unsigned, Optional<unsigned>>> getAllocSizeArgs() const;
   unsigned getVScaleRangeMin() const;
   Optional<unsigned> getVScaleRangeMax() const;
   UWTableKind getUWTableKind() const;

llvm/lib/IR/Attributes.cpp

@@ -745,9 +745,11 @@ Type *AttributeSet::getElementType() const {
   return SetNode ? SetNode->getAttributeType(Attribute::ElementType) : nullptr;
 }
 
-std::pair<unsigned, Optional<unsigned>> AttributeSet::getAllocSizeArgs() const {
-  return SetNode ? SetNode->getAllocSizeArgs()
-                 : std::pair<unsigned, Optional<unsigned>>(0, 0);
+Optional<std::pair<unsigned, Optional<unsigned>>>
+AttributeSet::getAllocSizeArgs() const {
+  if (SetNode)
+    return SetNode->getAllocSizeArgs();
+  return None;
 }
 
 unsigned AttributeSet::getVScaleRangeMin() const {
@@ -913,11 +915,11 @@ uint64_t AttributeSetNode::getDereferenceableOrNullBytes() const {
   return 0;
 }
 
-std::pair<unsigned, Optional<unsigned>>
+Optional<std::pair<unsigned, Optional<unsigned>>>
 AttributeSetNode::getAllocSizeArgs() const {
   if (auto A = findEnumAttribute(Attribute::AllocSize))
     return A->getAllocSizeArgs();
-  return std::make_pair(0, 0);
+  return None;
 }
 
 unsigned AttributeSetNode::getVScaleRangeMin() const {
@@ -1653,8 +1655,12 @@ AttrBuilder &AttrBuilder::addRawIntAttr(Attribute::AttrKind Kind,
   return addAttribute(Attribute::get(Ctx, Kind, Value));
 }
 
-std::pair<unsigned, Optional<unsigned>> AttrBuilder::getAllocSizeArgs() const {
-  return unpackAllocSizeArgs(getRawIntAttr(Attribute::AllocSize).value_or(0));
+Optional<std::pair<unsigned, Optional<unsigned>>>
+AttrBuilder::getAllocSizeArgs() const {
+  Attribute A = getAttribute(Attribute::AllocSize);
+  if (A.isValid())
+    return A.getAllocSizeArgs();
+  return None;
 }
 
 AttrBuilder &AttrBuilder::addAlignmentAttr(MaybeAlign Align) {

llvm/lib/IR/Verifier.cpp

@@ -2083,10 +2083,7 @@ void Verifier::verifyFunctionAttrs(FunctionType *FT, AttributeList Attrs,
           "Attribute 'jumptable' requires 'unnamed_addr'", V);
   }
 
-  if (Attrs.hasFnAttr(Attribute::AllocSize)) {
-    std::pair<unsigned, Optional<unsigned>> Args =
-        Attrs.getFnAttrs().getAllocSizeArgs();
-
+  if (auto Args = Attrs.getFnAttrs().getAllocSizeArgs()) {
     auto CheckParam = [&](StringRef Name, unsigned ParamNo) {
       if (ParamNo >= FT->getNumParams()) {
         CheckFailed("'allocsize' " + Name + " argument is out of bounds", V);
@@ -2103,10 +2100,10 @@ void Verifier::verifyFunctionAttrs(FunctionType *FT, AttributeList Attrs,
       return true;
     };
 
-    if (!CheckParam("element size", Args.first))
+    if (!CheckParam("element size", Args->first))
       return;
 
-    if (Args.second && !CheckParam("number of elements", *Args.second))
+    if (Args->second && !CheckParam("number of elements", *Args->second))
       return;
   }
 

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

@@ -545,12 +545,10 @@ Value *WebAssemblyLowerEmscriptenEHSjLj::wrapInvoke(CallBase *CI) {
     ArgAttributes.push_back(InvokeAL.getParamAttrs(I));
 
   AttrBuilder FnAttrs(CI->getContext(), InvokeAL.getFnAttrs());
-  if (FnAttrs.contains(Attribute::AllocSize)) {
+  if (auto Args = FnAttrs.getAllocSizeArgs()) {
     // The allocsize attribute (if any) referes to parameters by index and needs
     // to be adjusted.
-    unsigned SizeArg;
-    Optional<unsigned> NEltArg;
-    std::tie(SizeArg, NEltArg) = FnAttrs.getAllocSizeArgs();
+    auto [SizeArg, NEltArg] = *Args;
     SizeArg += 1;
     if (NEltArg)
       NEltArg = NEltArg.value() + 1;