[llvm] [IR][Attribute] Add support for intersecting AttributeLists; NFC (PR #109719)

via llvm-commits llvm-commits at lists.llvm.org
Mon Sep 23 14:01:23 PDT 2024


https://github.com/goldsteinn created https://github.com/llvm/llvm-project/pull/109719

Add support for taking the intersection of two AttributeLists s.t the
result list contains attributes that are valid in the context of both
inputs.

i.e if we have `nonnull align(32) noundef` intersected with `nonnull
align(16) dereferenceable(10)`, the result is `nonnull align(16)`.

Further it handles attributes that are not-droppable. For example
dropping `byval` can change the nature of a callsite/function so its
impossible to correct a correct intersection if its dropped from the
result. i.e `nonnull byval(i64)` intersected with `nonnull` is
invalid.

The motivation for the infrastructure is to enable sinking/hoisting
callsites with differing attributes.


>From 92ba0be0e8a18cc24314669430ea546fd7960c51 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Mon, 23 Sep 2024 15:56:06 -0500
Subject: [PATCH] [IR][Attribute] Add support for intersecting AttributeLists;
 NFC

Add support for taking the intersection of two AttributeLists s.t the
result list contains attributes that are valid in the context of both
inputs.

i.e if we have `nonnull align(32) noundef` intersected with `nonnull
align(16) dereferenceable(10)`, the result is `nonnull align(16)`.

Further it handles attributes that are not-droppable. For example
dropping `byval` can change the nature of a callsite/function so its
impossible to correct a correct intersection if its dropped from the
result. i.e `nonnull byval(i64)` intersected with `nonnull` is
invalid.

The motivation for the infrastructure is to enable sinking/hoisting
callsites with differing attributes.
---
 llvm/include/llvm/IR/Attributes.h    |  25 ++-
 llvm/include/llvm/IR/Attributes.td   |  93 ++++++----
 llvm/lib/IR/Attributes.cpp           | 130 +++++++++++++
 llvm/unittests/IR/AttributesTest.cpp | 268 +++++++++++++++++++++++++++
 llvm/utils/TableGen/Attributes.cpp   |  14 +-
 5 files changed, 497 insertions(+), 33 deletions(-)

diff --git a/llvm/include/llvm/IR/Attributes.h b/llvm/include/llvm/IR/Attributes.h
index 5a80a072dbbd27..ac0b00e2ccddbe 100644
--- a/llvm/include/llvm/IR/Attributes.h
+++ b/llvm/include/llvm/IR/Attributes.h
@@ -117,6 +117,10 @@ class Attribute {
   static bool canUseAsParamAttr(AttrKind Kind);
   static bool canUseAsRetAttr(AttrKind Kind);
 
+  static bool intersectWithAnd(AttrKind Kind);
+  static bool intersectWithMin(AttrKind Kind);
+  static bool intersectWithCustom(AttrKind Kind);
+
 private:
   AttributeImpl *pImpl = nullptr;
 
@@ -208,8 +212,15 @@ class Attribute {
   /// Return true if the target-dependent attribute is present.
   bool hasAttribute(StringRef Val) const;
 
+  /// Returns true if the attribute's kind can be represented as an enum (Enum,
+  /// Integer, Type, ConstantRange, or ConstantRangeList attribute).
+  bool hasKindAsEnum() const {
+    return isEnumAttribute() || isIntAttribute() || isTypeAttribute() ||
+           isConstantRangeAttribute() || isConstantRangeListAttribute();
+  }
+
   /// Return the attribute's kind as an enum (Attribute::AttrKind). This
-  /// requires the attribute to be an enum, integer, or type attribute.
+  /// requires the attribute be representable as an enum (see: `hasKindAsEnum`).
   Attribute::AttrKind getKindAsEnum() const;
 
   /// Return the attribute's value as an integer. This requires that the
@@ -383,6 +394,12 @@ class AttributeSet {
   [[nodiscard]] AttributeSet
   removeAttributes(LLVMContext &C, const AttributeMask &AttrsToRemove) const;
 
+  /// Try to intersect this AttributeSet with Other. Returns std::nullopt if
+  /// the two lists are inherently incompatible (imply different behavior, not
+  /// just analysis).
+  [[nodiscard]] std::optional<AttributeSet>
+  intersectWith(LLVMContext &C, AttributeSet Other) const;
+
   /// Return the number of attributes in this set.
   unsigned getNumAttributes() const;
 
@@ -775,6 +792,12 @@ class AttributeList {
   addAllocSizeParamAttr(LLVMContext &C, unsigned ArgNo, unsigned ElemSizeArg,
                         const std::optional<unsigned> &NumElemsArg);
 
+  /// Try to intersect this AttributeList with Other. Returns std::nullopt if
+  /// the two lists are inherently incompatible (imply different behavior, not
+  /// just analysis).
+  [[nodiscard]] std::optional<AttributeList>
+  intersectAttributes(LLVMContext &C, AttributeList Other) const;
+
   //===--------------------------------------------------------------------===//
   // AttributeList Accessors
   //===--------------------------------------------------------------------===//
diff --git a/llvm/include/llvm/IR/Attributes.td b/llvm/include/llvm/IR/Attributes.td
index 9044d127b47946..ca24627912f27f 100644
--- a/llvm/include/llvm/IR/Attributes.td
+++ b/llvm/include/llvm/IR/Attributes.td
@@ -22,6 +22,37 @@ def ParamAttr : AttrProperty;
 /// Can be used as return attribute.
 def RetAttr : AttrProperty;
 
+
+
+/// Intersection rules. Used for example in sinking/hoisting two
+/// callbases to find a set of attributes that apply to both.
+/// If no rule is specified, the assumed rule is that the attrs
+/// must be equal, otherwise the intersection will fail. Having
+/// any rule implies that it is legal to drop the attribute.
+/// Note, there are some attributes we can (probably) legally drop
+/// but are intentionally excluded as of now. Those include:
+///     - initializes
+///     - allockind
+///     - allocsize
+///     - minsize
+///     - optsize
+///     - optnone
+///     - optdebug
+///     - optforfuzzing    
+///
+/// When intersecting take the AND of the two attrs.
+/// Invalid for Int/ConstantRange/ConstantRangeList attrs.
+def IntersectAnd : AttrProperty;
+
+/// When intersecting take the min value of the two attrs.
+/// Only valid for Int attrs.
+def IntersectMin : AttrProperty;
+
+/// When intersecting rely on some user defined code.
+def IntersectCustom : AttrProperty;
+
+    
+
 /// Attribute base class.
 class Attr<string S, list<AttrProperty> P> {
   // String representation of this attribute in the IR.
@@ -54,17 +85,17 @@ class ConstantRangeListAttr<string S, list<AttrProperty> P> : Attr<S, P>;
 
 /// Alignment of parameter (5 bits) stored as log2 of alignment with +1 bias.
 /// 0 means unaligned (different from align(1)).
-def Alignment : IntAttr<"align", [ParamAttr, RetAttr]>;
+def Alignment : IntAttr<"align", [ParamAttr, RetAttr, IntersectCustom]>;
 
 /// Parameter of a function that tells us the alignment of an allocation, as in
 /// aligned_alloc and aligned ::operator::new.
-def AllocAlign: EnumAttr<"allocalign", [ParamAttr]>;
+def AllocAlign: EnumAttr<"allocalign", [ParamAttr, IntersectAnd]>;
 
 /// Describes behavior of an allocator function in terms of known properties.
 def AllocKind: IntAttr<"allockind", [FnAttr]>;
 
 /// Parameter is the pointer to be manipulated by the allocator function.
-def AllocatedPointer : EnumAttr<"allocptr", [ParamAttr]>;
+def AllocatedPointer : EnumAttr<"allocptr", [ParamAttr, IntersectAnd]>;
 
 /// The result of the function is guaranteed to point to a number of bytes that
 /// we can determine if we know the value of the function's arguments.
@@ -84,23 +115,23 @@ def ByVal : TypeAttr<"byval", [ParamAttr]>;
 def ByRef : TypeAttr<"byref", [ParamAttr]>;
 
 /// Parameter or return value may not contain uninitialized or poison bits.
-def NoUndef : EnumAttr<"noundef", [ParamAttr, RetAttr]>;
+def NoUndef : EnumAttr<"noundef", [ParamAttr, RetAttr, IntersectAnd]>;
 
 /// Marks function as being in a cold path.
-def Cold : EnumAttr<"cold", [FnAttr]>;
+def Cold : EnumAttr<"cold", [FnAttr, IntersectAnd]>;
 
 /// Can only be moved to control-equivalent blocks.
-def Convergent : EnumAttr<"convergent", [FnAttr]>;
+def Convergent : EnumAttr<"convergent", [FnAttr, IntersectAnd]>;
 
 /// Marks function as being in a hot path and frequently called.
-def Hot: EnumAttr<"hot", [FnAttr]>;
+def Hot: EnumAttr<"hot", [FnAttr, IntersectAnd]>;
 
 /// Pointer is known to be dereferenceable.
-def Dereferenceable : IntAttr<"dereferenceable", [ParamAttr, RetAttr]>;
+def Dereferenceable : IntAttr<"dereferenceable", [ParamAttr, RetAttr, IntersectMin]>;
 
 /// Pointer is either null or dereferenceable.
 def DereferenceableOrNull : IntAttr<"dereferenceable_or_null",
-                                    [ParamAttr, RetAttr]>;
+                                    [ParamAttr, RetAttr, IntersectMin]>;
 
 /// Do not instrument function with sanitizers.
 def DisableSanitizerInstrumentation: EnumAttr<"disable_sanitizer_instrumentation", [FnAttr]>;
@@ -122,7 +153,7 @@ def InAlloca : TypeAttr<"inalloca", [ParamAttr]>;
 def Initializes : ConstantRangeListAttr<"initializes", [ParamAttr]>;
 
 /// Source said inlining was desirable.
-def InlineHint : EnumAttr<"inlinehint", [FnAttr]>;
+def InlineHint : EnumAttr<"inlinehint", [FnAttr, IntersectAnd]>;
 
 /// Force argument to be passed in register.
 def InReg : EnumAttr<"inreg", [ParamAttr, RetAttr]>;
@@ -131,10 +162,10 @@ def InReg : EnumAttr<"inreg", [ParamAttr, RetAttr]>;
 def JumpTable : EnumAttr<"jumptable", [FnAttr]>;
 
 /// Memory effects of the function.
-def Memory : IntAttr<"memory", [FnAttr]>;
+def Memory : IntAttr<"memory", [FnAttr, IntersectCustom]>;
 
 /// Forbidden floating-point classes.
-def NoFPClass : IntAttr<"nofpclass", [ParamAttr, RetAttr]>;
+def NoFPClass : IntAttr<"nofpclass", [ParamAttr, RetAttr, IntersectCustom]>;
 
 /// Function must be optimized for size first.
 def MinSize : EnumAttr<"minsize", [FnAttr]>;
@@ -146,16 +177,16 @@ def Naked : EnumAttr<"naked", [FnAttr]>;
 def Nest : EnumAttr<"nest", [ParamAttr]>;
 
 /// Considered to not alias after call.
-def NoAlias : EnumAttr<"noalias", [ParamAttr, RetAttr]>;
+def NoAlias : EnumAttr<"noalias", [ParamAttr, RetAttr, IntersectAnd]>;
 
 /// Callee isn't recognized as a builtin.
 def NoBuiltin : EnumAttr<"nobuiltin", [FnAttr]>;
 
 /// Function cannot enter into caller's translation unit.
-def NoCallback : EnumAttr<"nocallback", [FnAttr]>;
+def NoCallback : EnumAttr<"nocallback", [FnAttr, IntersectAnd]>;
 
 /// Function creates no aliases of pointer.
-def NoCapture : EnumAttr<"nocapture", [ParamAttr]>;
+def NoCapture : EnumAttr<"nocapture", [ParamAttr, IntersectAnd]>;
 
 /// Call cannot be duplicated.
 def NoDuplicate : EnumAttr<"noduplicate", [FnAttr]>;
@@ -164,10 +195,10 @@ def NoDuplicate : EnumAttr<"noduplicate", [FnAttr]>;
 def NoExt : EnumAttr<"noext", [ParamAttr, RetAttr]>;
 
 /// Function does not deallocate memory.
-def NoFree : EnumAttr<"nofree", [FnAttr, ParamAttr]>;
+def NoFree : EnumAttr<"nofree", [FnAttr, ParamAttr, IntersectAnd]>;
 
 /// Argument is dead if the call unwinds.
-def DeadOnUnwind : EnumAttr<"dead_on_unwind", [ParamAttr]>;
+def DeadOnUnwind : EnumAttr<"dead_on_unwind", [ParamAttr, IntersectAnd]>;
 
 /// Disable implicit floating point insts.
 def NoImplicitFloat : EnumAttr<"noimplicitfloat", [FnAttr]>;
@@ -182,19 +213,19 @@ def NonLazyBind : EnumAttr<"nonlazybind", [FnAttr]>;
 def NoMerge : EnumAttr<"nomerge", [FnAttr]>;
 
 /// Pointer is known to be not null.
-def NonNull : EnumAttr<"nonnull", [ParamAttr, RetAttr]>;
+def NonNull : EnumAttr<"nonnull", [ParamAttr, RetAttr, IntersectAnd]>;
 
 /// The function does not recurse.
-def NoRecurse : EnumAttr<"norecurse", [FnAttr]>;
+def NoRecurse : EnumAttr<"norecurse", [FnAttr, IntersectAnd]>;
 
 /// Disable redzone.
 def NoRedZone : EnumAttr<"noredzone", [FnAttr]>;
 
 /// Mark the function as not returning.
-def NoReturn : EnumAttr<"noreturn", [FnAttr]>;
+def NoReturn : EnumAttr<"noreturn", [FnAttr, IntersectAnd]>;
 
 /// Function does not synchronize.
-def NoSync : EnumAttr<"nosync", [FnAttr]>;
+def NoSync : EnumAttr<"nosync", [FnAttr, IntersectAnd]>;
 
 /// Disable Indirect Branch Tracking.
 def NoCfCheck : EnumAttr<"nocf_check", [FnAttr]>;
@@ -207,7 +238,7 @@ def NoProfile : EnumAttr<"noprofile", [FnAttr]>;
 def SkipProfile : EnumAttr<"skipprofile", [FnAttr]>;
 
 /// Function doesn't unwind stack.
-def NoUnwind : EnumAttr<"nounwind", [FnAttr]>;
+def NoUnwind : EnumAttr<"nounwind", [FnAttr, IntersectAnd]>;
 
 /// No SanitizeBounds instrumentation.
 def NoSanitizeBounds : EnumAttr<"nosanitize_bounds", [FnAttr]>;
@@ -234,16 +265,16 @@ def OptimizeNone : EnumAttr<"optnone", [FnAttr]>;
 def Preallocated : TypeAttr<"preallocated", [FnAttr, ParamAttr]>;
 
 /// Parameter or return value is within the specified range.
-def Range : ConstantRangeAttr<"range", [ParamAttr, RetAttr]>;
+def Range : ConstantRangeAttr<"range", [ParamAttr, RetAttr, IntersectCustom]>;
 
 /// Function does not access memory.
-def ReadNone : EnumAttr<"readnone", [ParamAttr]>;
+def ReadNone : EnumAttr<"readnone", [ParamAttr, IntersectAnd]>;
 
 /// Function only reads from memory.
-def ReadOnly : EnumAttr<"readonly", [ParamAttr]>;
+def ReadOnly : EnumAttr<"readonly", [ParamAttr, IntersectAnd]>;
 
 /// Return value is always equal to this argument.
-def Returned : EnumAttr<"returned", [ParamAttr]>;
+def Returned : EnumAttr<"returned", [ParamAttr, IntersectAnd]>;
 
 /// Parameter is required to be a trivial constant.
 def ImmArg : EnumAttr<"immarg", [ParamAttr]>;
@@ -265,7 +296,7 @@ def SExt : EnumAttr<"signext", [ParamAttr, RetAttr]>;
 def StackAlignment : IntAttr<"alignstack", [FnAttr, ParamAttr]>;
 
 /// Function can be speculated.
-def Speculatable : EnumAttr<"speculatable", [FnAttr]>;
+def Speculatable : EnumAttr<"speculatable", [FnAttr, IntersectAnd]>;
 
 /// Stack protection.
 def StackProtect : EnumAttr<"ssp", [FnAttr]>;
@@ -332,19 +363,19 @@ def UWTable : IntAttr<"uwtable", [FnAttr]>;
 def VScaleRange : IntAttr<"vscale_range", [FnAttr]>;
 
 /// Function always comes back to callsite.
-def WillReturn : EnumAttr<"willreturn", [FnAttr]>;
+def WillReturn : EnumAttr<"willreturn", [FnAttr, IntersectAnd]>;
 
 /// Pointer argument is writable.
-def Writable : EnumAttr<"writable", [ParamAttr]>;
+def Writable : EnumAttr<"writable", [ParamAttr, IntersectAnd]>;
 
 /// Function only writes to memory.
-def WriteOnly : EnumAttr<"writeonly", [ParamAttr]>;
+def WriteOnly : EnumAttr<"writeonly", [ParamAttr, IntersectAnd]>;
 
 /// Zero extended before/after call.
 def ZExt : EnumAttr<"zeroext", [ParamAttr, RetAttr]>;
 
 /// Function is required to make Forward Progress.
-def MustProgress : EnumAttr<"mustprogress", [FnAttr]>;
+def MustProgress : EnumAttr<"mustprogress", [FnAttr, IntersectAnd]>;
 
 /// Function is a presplit coroutine.
 def PresplitCoroutine : EnumAttr<"presplitcoroutine", [FnAttr]>;
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index fa124e46483dce..2e54ef1aa3e00c 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -727,6 +727,9 @@ enum AttributeProperty {
   FnAttr = (1 << 0),
   ParamAttr = (1 << 1),
   RetAttr = (1 << 2),
+  IntersectAnd = (1 << 3),
+  IntersectMin = (1 << 4),
+  IntersectCustom = (1 << 5),
 };
 
 #define GET_ATTR_PROP_TABLE
@@ -751,6 +754,16 @@ bool Attribute::canUseAsRetAttr(AttrKind Kind) {
   return hasAttributeProperty(Kind, AttributeProperty::RetAttr);
 }
 
+bool Attribute::intersectWithAnd(AttrKind Kind) {
+  return hasAttributeProperty(Kind, AttributeProperty::IntersectAnd);
+}
+bool Attribute::intersectWithMin(AttrKind Kind) {
+  return hasAttributeProperty(Kind, AttributeProperty::IntersectMin);
+}
+bool Attribute::intersectWithCustom(AttrKind Kind) {
+  return hasAttributeProperty(Kind, AttributeProperty::IntersectCustom);
+}
+
 //===----------------------------------------------------------------------===//
 // AttributeImpl Definition
 //===----------------------------------------------------------------------===//
@@ -903,6 +916,98 @@ AttributeSet AttributeSet::removeAttributes(LLVMContext &C,
   return get(C, B);
 }
 
+std::optional<AttributeSet>
+AttributeSet::intersectWith(LLVMContext &C, AttributeSet Other) const {
+  if (*this == Other)
+    return *this;
+  AttrBuilder Intersected(C);
+  // Get common set of all attributes then handle each attr according to its
+  // intersect rule.
+  AttributeSet Merged = addAttributes(C, Other);
+  for (Attribute Attr : Merged) {
+    // Only supporting enum attrs for now.
+    if (!Attr.hasKindAsEnum())
+      return std::nullopt;
+
+    Attribute::AttrKind Kind = Attr.getKindAsEnum();
+    std::optional<Attribute> Attr0, Attr1;
+    if (hasAttribute(Kind))
+      Attr0 = getAttribute(Kind);
+    if (Other.hasAttribute(Kind))
+      Attr1 = Other.getAttribute(Kind);
+
+    auto IntersectEq = [&]() {
+      if (!Attr0 || !Attr1)
+        return false;
+      if (*Attr0 != *Attr1)
+        return false;
+      Intersected.addAttribute(Attr);
+      return true;
+    };
+
+    // Attribute we can intersect with "and"
+    if (Attribute::intersectWithAnd(Kind)) {
+      assert(Attribute::isEnumAttrKind(Kind) &&
+             "Invalid attr type of intersectAnd");
+      if (Attr0 && Attr1)
+        Intersected.addAttribute(Kind);
+      continue;
+    }
+    bool BothValid = Attr0 && Attr1 && Attr0->isValid() && Attr1->isValid();
+
+    // Attribute we can intersect with "min"
+    if (Attribute::intersectWithMin(Kind)) {
+      assert(Attribute::isIntAttrKind(Kind) &&
+             "Invalid attr type of intersectMin");
+      if (!BothValid)
+        continue;
+
+      uint64_t NewVal = std::min(getAttribute(Kind).getValueAsInt(),
+                                 Other.getAttribute(Kind).getValueAsInt());
+      Intersected.addRawIntAttr(Kind, NewVal);
+      continue;
+    }
+    // Attribute we can intersect but need a custom rule for.
+    if (Attribute::intersectWithCustom(Kind)) {
+      switch (Kind) {
+      case Attribute::Alignment:
+        if (BothValid)
+          Intersected.addAlignmentAttr(std::min(
+              getAlignment().valueOrOne(), Other.getAlignment().valueOrOne()));
+        break;
+      case Attribute::Memory:
+        if (BothValid)
+          Intersected.addMemoryAttr(getMemoryEffects() |
+                                    Other.getMemoryEffects());
+        break;
+      case Attribute::NoFPClass:
+        if (BothValid)
+          Intersected.addNoFPClassAttr(getNoFPClass() & Other.getNoFPClass());
+        break;
+      case Attribute::Range:
+        if (BothValid) {
+          ConstantRange Range0 = getAttribute(Kind).getRange();
+          ConstantRange Range1 = Other.getAttribute(Kind).getRange();
+          ConstantRange NewRange = Range0.unionWith(Range1);
+          if (!NewRange.isFullSet())
+            Intersected.addRangeAttr(NewRange);
+        }
+        break;
+      default:
+        llvm_unreachable("Unknown attribute with custom intersection rule");
+      }
+      continue;
+    }
+
+    // Attributes with no intersection rule. Only intersect if they are equal.
+    // Otherwise fail.
+    if (!IntersectEq())
+      return std::nullopt;
+  }
+
+  return get(C, Intersected);
+}
+
 unsigned AttributeSet::getNumAttributes() const {
   return SetNode ? SetNode->getNumAttributes() : 0;
 }
@@ -1614,6 +1719,31 @@ AttributeList AttributeList::addAllocSizeParamAttr(
   return addParamAttributes(C, Index, B);
 }
 
+std::optional<AttributeList>
+AttributeList::intersectAttributes(LLVMContext &C, AttributeList Other) const {
+  // Trivial case, the two lists are equal.
+  if (*this == Other)
+    return *this;
+
+  // At least for now, only intersect lists with same number of params.
+  if (getNumAttrSets() != Other.getNumAttrSets())
+    return std::nullopt;
+
+  AttributeList IntersectedAttrs{};
+  for (unsigned Idx : indexes()) {
+    auto IntersectedAB =
+        getAttributes(Idx).intersectWith(C, Other.getAttributes(Idx));
+    // If any index fails to intersect, fail.
+    if (!IntersectedAB)
+      return std::nullopt;
+
+    IntersectedAttrs =
+        IntersectedAttrs.setAttributesAtIndex(C, Idx, *IntersectedAB);
+  }
+
+  return IntersectedAttrs;
+}
+
 //===----------------------------------------------------------------------===//
 // AttributeList Accessor Methods
 //===----------------------------------------------------------------------===//
diff --git a/llvm/unittests/IR/AttributesTest.cpp b/llvm/unittests/IR/AttributesTest.cpp
index da72fa14510cbe..2c22b960e50265 100644
--- a/llvm/unittests/IR/AttributesTest.cpp
+++ b/llvm/unittests/IR/AttributesTest.cpp
@@ -8,6 +8,7 @@
 
 #include "llvm/IR/Attributes.h"
 #include "llvm-c/Core.h"
+#include "llvm/ADT/FloatingPointMode.h"
 #include "llvm/AsmParser/Parser.h"
 #include "llvm/IR/AttributeMask.h"
 #include "llvm/IR/ConstantRange.h"
@@ -386,4 +387,271 @@ TEST(Attributes, CalleeAttributes) {
   }
 }
 
+TEST(Attributes, SetIntersect) {
+  LLVMContext C0, C1;
+  std::optional<AttributeSet> Res;
+  auto BuildAttr = [&](LLVMContext &C, Attribute::AttrKind Kind, uint64_t Int,
+                       Type *Ty, ConstantRange &CR,
+                       ArrayRef<ConstantRange> CRList) {
+    if (Attribute::isEnumAttrKind(Kind))
+      return Attribute::get(C, Kind);
+    if (Attribute::isTypeAttrKind(Kind))
+      return Attribute::get(C, Kind, Ty);
+    if (Attribute::isIntAttrKind(Kind))
+      return Attribute::get(C, Kind, Int);
+    if (Attribute::isConstantRangeAttrKind(Kind))
+      return Attribute::get(C, Kind, CR);
+    if (Attribute::isConstantRangeListAttrKind(Kind))
+      return Attribute::get(C, Kind, CRList);
+    std::abort();
+  };
+  for (unsigned i = Attribute::AttrKind::None + 1,
+                e = Attribute::AttrKind::EndAttrKinds;
+       i < e; ++i) {
+    Attribute::AttrKind Kind = static_cast<Attribute::AttrKind>(i);
+
+    Attribute::AttrKind Other =
+        Kind == Attribute::NoUndef ? Attribute::NonNull : Attribute::NoUndef;
+    AttributeSet AS0, AS1;
+    AttrBuilder AB0(C0);
+    AttrBuilder AB1(C1);
+    uint64_t V0, V1;
+    V0 = 0;
+    V1 = 0;
+    if (Attribute::intersectWithCustom(Kind)) {
+      switch (Kind) {
+      case Attribute::Alignment:
+        V0 = 2;
+        V1 = 4;
+        break;
+      case Attribute::Memory:
+        V0 = MemoryEffects::readOnly().toIntValue();
+        V1 = MemoryEffects::none().toIntValue();
+        break;
+      case Attribute::NoFPClass:
+        V0 = FPClassTest::fcNan | FPClassTest::fcInf;
+        V1 = FPClassTest::fcNan;
+        break;
+      case Attribute::Range:
+        break;
+      default:
+        ASSERT_FALSE(true);
+      }
+    } else {
+      V0 = (i & 2) + 1;
+      V1 = (2 - (i & 2)) + 1;
+    }
+
+    ConstantRange CR0(APInt(32, 0), APInt(32, 10));
+    ConstantRange CR1(APInt(32, 15), APInt(32, 20));
+    ArrayRef<ConstantRange> CRL0 = {CR0};
+    ArrayRef<ConstantRange> CRL1 = {CR0, CR1};
+    Type *T0 = Type::getInt32Ty(C0);
+    Type *T1 = Type::getInt64Ty(C0);
+    Attribute Attr0 = BuildAttr(C0, Kind, V0, T0, CR0, CRL0);
+    Attribute Attr1 = BuildAttr(
+        C1, Attribute::isEnumAttrKind(Kind) ? Other : Kind, V1, T1, CR1, CRL1);
+    bool CanDrop = Attribute::intersectWithAnd(Kind) ||
+                   Attribute::intersectWithMin(Kind) ||
+                   Attribute::intersectWithCustom(Kind);
+
+    AB0.addAttribute(Attr0);
+    AB1.addAttribute(Attr1);
+
+    Res = AS0.intersectWith(C0, AS1);
+    ASSERT_TRUE(Res.has_value());
+    ASSERT_EQ(AS0, *Res);
+
+    AS0 = AttributeSet::get(C0, AB0);
+    Res = AS0.intersectWith(C0, AS1);
+    ASSERT_EQ(Res.has_value(), CanDrop);
+    if (CanDrop)
+      ASSERT_FALSE(Res->hasAttributes());
+
+    AS1 = AttributeSet::get(C1, AB0);
+    Res = AS0.intersectWith(C0, AS1);
+    ASSERT_TRUE(Res.has_value());
+    ASSERT_EQ(AS0, *Res);
+
+    AS1 = AttributeSet::get(C1, AB1);
+    Res = AS0.intersectWith(C0, AS1);
+    if (!CanDrop) {
+      ASSERT_FALSE(Res.has_value());
+      continue;
+    }
+    if (Attribute::intersectWithAnd(Kind)) {
+      ASSERT_TRUE(Res.has_value());
+      ASSERT_FALSE(Res->hasAttributes());
+
+      AS1 = AS1.addAttribute(C1, Kind);
+      Res = AS0.intersectWith(C0, AS1);
+      ASSERT_TRUE(Res.has_value());
+      ASSERT_TRUE(Res->hasAttributes());
+      ASSERT_TRUE(Res->hasAttribute(Kind));
+      ASSERT_FALSE(Res->hasAttribute(Other));
+    } else if (Attribute::intersectWithMin(Kind)) {
+      ASSERT_TRUE(Res.has_value());
+      ASSERT_TRUE(Res->hasAttributes());
+      ASSERT_TRUE(Res->hasAttribute(Kind));
+      ASSERT_EQ(Res->getAttribute(Kind).getValueAsInt(), std::min(V0, V1));
+    } else if (Attribute::intersectWithCustom(Kind)) {
+      ASSERT_TRUE(Res.has_value());
+      ASSERT_TRUE(Res->hasAttributes());
+      ASSERT_TRUE(Res->hasAttribute(Kind));
+
+      switch (Kind) {
+      case Attribute::Alignment:
+        ASSERT_EQ(Res->getAlignment().valueOrOne(), MaybeAlign(2).valueOrOne());
+        break;
+      case Attribute::Memory:
+        ASSERT_EQ(Res->getMemoryEffects(), MemoryEffects::readOnly());
+        break;
+      case Attribute::NoFPClass:
+        ASSERT_EQ(Res->getNoFPClass(), FPClassTest::fcNan);
+        break;
+      case Attribute::Range:
+        ASSERT_EQ(Res->getAttribute(Kind).getRange(),
+                  ConstantRange(APInt(32, 0), APInt(32, 20)));
+        break;
+      default:
+        ASSERT_FALSE(true);
+      }
+    }
+    AS0 = AS0.addAttribute(C0, Attribute::AlwaysInline);
+    ASSERT_FALSE(AS0.intersectWith(C0, AS1).has_value());
+  }
+}
+
+TEST(Attributes, ListIntersect) {
+  LLVMContext C;
+  AttributeList AL0;
+  AttributeList AL1;
+  std::optional<AttributeList> Res;
+  AL0 = AL0.addRetAttribute(C, Attribute::NoUndef);
+  AL1 = AL1.addRetAttribute(C, Attribute::NoUndef);
+
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_EQ(AL0, *Res);
+
+  AL0 = AL0.addParamAttribute(C, 1, Attribute::NoUndef);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_FALSE(Res.has_value());
+
+  AL1 = AL1.addParamAttribute(C, 2, Attribute::NoUndef);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_FALSE(Res.has_value());
+
+  AL0 = AL0.addParamAttribute(C, 2, Attribute::NoUndef);
+  AL1 = AL1.addParamAttribute(C, 1, Attribute::NoUndef);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_EQ(AL0, *Res);
+
+  AL0 = AL0.addParamAttribute(C, 2, Attribute::NonNull);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_NE(AL0, *Res);
+  ASSERT_TRUE(Res->hasRetAttr(Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(1, Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(2, Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::NonNull));
+
+  AL0 = AL0.addRetAttribute(C, Attribute::NonNull);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_NE(AL0, *Res);
+  ASSERT_TRUE(Res->hasRetAttr(Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasRetAttr(Attribute::NonNull));
+  ASSERT_TRUE(Res->hasParamAttr(1, Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(2, Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::NonNull));
+
+  AL0 = AL0.addFnAttribute(C, Attribute::ReadOnly);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_NE(AL0, *Res);
+  ASSERT_FALSE(Res->hasFnAttr(Attribute::ReadOnly));
+  ASSERT_TRUE(Res->hasRetAttr(Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasRetAttr(Attribute::NonNull));
+  ASSERT_TRUE(Res->hasParamAttr(1, Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(2, Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::NonNull));
+
+  AL1 = AL1.addFnAttribute(C, Attribute::ReadOnly);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_NE(AL0, *Res);
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::ReadOnly));
+  ASSERT_TRUE(Res->hasRetAttr(Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasRetAttr(Attribute::NonNull));
+  ASSERT_TRUE(Res->hasParamAttr(1, Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(2, Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::NonNull));
+
+  AL1 = AL1.addFnAttribute(C, Attribute::AlwaysInline);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_FALSE(Res.has_value());
+
+  AL0 = AL0.addFnAttribute(C, Attribute::AlwaysInline);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::AlwaysInline));
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::ReadOnly));
+  ASSERT_TRUE(Res->hasRetAttr(Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasRetAttr(Attribute::NonNull));
+  ASSERT_TRUE(Res->hasParamAttr(1, Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(2, Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::NonNull));
+
+  AL1 = AL1.addParamAttribute(C, 2, Attribute::ReadNone);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::AlwaysInline));
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::ReadOnly));
+  ASSERT_TRUE(Res->hasRetAttr(Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasRetAttr(Attribute::NonNull));
+  ASSERT_TRUE(Res->hasParamAttr(1, Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(2, Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::NonNull));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::ReadNone));
+
+  AL1 = AL1.addParamAttribute(C, 3, Attribute::ReadNone);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_FALSE(Res.has_value());
+
+  AL0 = AL0.addParamAttribute(C, 3, Attribute::ReadNone);
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::AlwaysInline));
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::ReadOnly));
+  ASSERT_TRUE(Res->hasRetAttr(Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasRetAttr(Attribute::NonNull));
+  ASSERT_TRUE(Res->hasParamAttr(1, Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(2, Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::NonNull));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::ReadNone));
+  ASSERT_TRUE(Res->hasParamAttr(3, Attribute::ReadNone));
+
+  AL0 = AL0.addParamAttribute(
+      C, {3}, Attribute::get(C, Attribute::ByVal, Type::getInt32Ty(C)));
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_FALSE(Res.has_value());
+
+  AL1 = AL1.addParamAttribute(
+      C, {3}, Attribute::get(C, Attribute::ByVal, Type::getInt32Ty(C)));
+  Res = AL0.intersectAttributes(C, AL1);
+  ASSERT_TRUE(Res.has_value());
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::AlwaysInline));
+  ASSERT_TRUE(Res->hasFnAttr(Attribute::ReadOnly));
+  ASSERT_TRUE(Res->hasRetAttr(Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasRetAttr(Attribute::NonNull));
+  ASSERT_TRUE(Res->hasParamAttr(1, Attribute::NoUndef));
+  ASSERT_TRUE(Res->hasParamAttr(2, Attribute::NoUndef));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::NonNull));
+  ASSERT_FALSE(Res->hasParamAttr(2, Attribute::ReadNone));
+  ASSERT_TRUE(Res->hasParamAttr(3, Attribute::ReadNone));
+  ASSERT_TRUE(Res->hasParamAttr(3, Attribute::ByVal));
+}
+
 } // end anonymous namespace
diff --git a/llvm/utils/TableGen/Attributes.cpp b/llvm/utils/TableGen/Attributes.cpp
index 8d16ff89aae0f2..2d2a9af186fd55 100644
--- a/llvm/utils/TableGen/Attributes.cpp
+++ b/llvm/utils/TableGen/Attributes.cpp
@@ -8,6 +8,7 @@
 
 #include "llvm/TableGen/Record.h"
 #include "llvm/TableGen/TableGenBackend.h"
+#include "llvm/TableGen/Error.h"
 #include <vector>
 using namespace llvm;
 
@@ -117,10 +118,21 @@ void Attributes::emitAttributeProperties(raw_ostream &OS) {
   OS << "static const uint8_t AttrPropTable[] = {\n";
   for (StringRef KindName : {"EnumAttr", "TypeAttr", "IntAttr",
                              "ConstantRangeAttr", "ConstantRangeListAttr"}) {
+    bool AllowIntersectAnd = KindName == "EnumAttr";
+    bool AllowIntersectMin = KindName == "IntAttr";
     for (auto *A : Records.getAllDerivedDefinitions(KindName)) {
       OS << "0";
-      for (Init *P : *A->getValueAsListInit("Properties"))
+      for (Init *P : *A->getValueAsListInit("Properties")) {
+        if (!AllowIntersectAnd &&
+            cast<DefInit>(P)->getDef()->getName() == "IntersectAnd")
+          PrintFatalError(
+              "'IntersectAnd' only compatible with 'EnumAttr' or 'TypeAttr'");
+        if (!AllowIntersectMin &&
+            cast<DefInit>(P)->getDef()->getName() == "IntersectMin")
+          PrintFatalError("'IntersectMin' only compatible with 'IntAttr'");
+
         OS << " | AttributeProperty::" << cast<DefInit>(P)->getDef()->getName();
+      }
       OS << ",\n";
     }
   }



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