From ed8d55718f937d532ed9eb52e7c3ce86c4600652 Mon Sep 17 00:00:00 2001
From: Zahira Ammarguellat <zahira.ammarguellat@intel.com>
Date: Tue, 31 Dec 2024 07:03:19 -0800
Subject: [PATCH] Reland https://github.com/llvm/llvm-project/pull/114899

---
 .../include/clang/Basic/AttributeCommonInfo.h | 14 +++++
 clang/lib/Basic/Attributes.cpp                | 26 ++++++++-
 clang/utils/TableGen/ClangAttrEmitter.cpp     | 58 ++++++++++++++++---
 3 files changed, 87 insertions(+), 11 deletions(-)

diff --git a/clang/include/clang/Basic/AttributeCommonInfo.h b/clang/include/clang/Basic/AttributeCommonInfo.h
index 5f024b4b5fd78..04b68c5a1d8dd 100644
--- a/clang/include/clang/Basic/AttributeCommonInfo.h
+++ b/clang/include/clang/Basic/AttributeCommonInfo.h
@@ -67,6 +67,20 @@ class AttributeCommonInfo {
     IgnoredAttribute,
     UnknownAttribute,
   };
+  enum class Scope {
+    NONE,
+    CLANG,
+    GNU,
+    MSVC,
+    OMP,
+    HLSL,
+    GSL,
+    RISCV,
+    INTEL,
+    SYCL,
+    CL,
+    SYCL_DETAIL
+  };
 
 private:
   const IdentifierInfo *AttrName = nullptr;
diff --git a/clang/lib/Basic/Attributes.cpp b/clang/lib/Basic/Attributes.cpp
index 9577277d85f81..960a7f7bc18af 100644
--- a/clang/lib/Basic/Attributes.cpp
+++ b/clang/lib/Basic/Attributes.cpp
@@ -17,6 +17,9 @@
 #include "clang/Basic/ParsedAttrInfo.h"
 #include "clang/Basic/TargetInfo.h"
 
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringSwitch.h"
+
 using namespace clang;
 
 static int hasAttributeImpl(AttributeCommonInfo::Syntax Syntax, StringRef Name,
@@ -156,13 +159,32 @@ std::string AttributeCommonInfo::getNormalizedFullName() const {
   return static_cast<std::string>(
       normalizeName(getAttrName(), getScopeName(), getSyntax()));
 }
+static AttributeCommonInfo::Scope
+getScopeFromNormalizedScopeName(StringRef ScopeName) {
+  return llvm::StringSwitch<AttributeCommonInfo::Scope>(ScopeName)
+      .Case("", AttributeCommonInfo::Scope::NONE)
+      .Case("clang", AttributeCommonInfo::Scope::CLANG)
+      .Case("gnu", AttributeCommonInfo::Scope::GNU)
+      .Case("gsl", AttributeCommonInfo::Scope::GSL)
+      .Case("hlsl", AttributeCommonInfo::Scope::HLSL)
+      .Case("msvc", AttributeCommonInfo::Scope::MSVC)
+      .Case("omp", AttributeCommonInfo::Scope::OMP)
+      .Case("riscv", AttributeCommonInfo::Scope::RISCV)
+      .Case("intel", AttributeCommonInfo::Scope::INTEL)
+      .Case("sycl", AttributeCommonInfo::Scope::SYCL)
+      .Case("cl", AttributeCommonInfo::Scope::CL)
+      .Case("__sycl_detail__", AttributeCommonInfo::Scope::SYCL_DETAIL);
+}
 
 unsigned AttributeCommonInfo::calculateAttributeSpellingListIndex() const {
   // Both variables will be used in tablegen generated
   // attribute spell list index matching code.
   auto Syntax = static_cast<AttributeCommonInfo::Syntax>(getSyntax());
-  StringRef Scope = normalizeAttrScopeName(getScopeName(), Syntax);
-  StringRef Name = normalizeAttrName(getAttrName(), Scope, Syntax);
+  StringRef ScopeName = normalizeAttrScopeName(getScopeName(), Syntax);
+  StringRef Name = normalizeAttrName(getAttrName(), ScopeName, Syntax);
+
+  AttributeCommonInfo::Scope ComputedScope =
+      getScopeFromNormalizedScopeName(ScopeName);
 
 #include "clang/Sema/AttrSpellingListIndex.inc"
 }
diff --git a/clang/utils/TableGen/ClangAttrEmitter.cpp b/clang/utils/TableGen/ClangAttrEmitter.cpp
index ebc1db374c775..ca6398b2c4a7c 100644
--- a/clang/utils/TableGen/ClangAttrEmitter.cpp
+++ b/clang/utils/TableGen/ClangAttrEmitter.cpp
@@ -3851,19 +3851,59 @@ void EmitClangAttrSpellingListIndex(const RecordKeeper &Records,
     const Record &R = *I.second;
     std::vector<FlattenedSpelling> Spellings = GetFlattenedSpellings(R);
     OS << "  case AT_" << I.first << ": {\n";
-    for (unsigned I = 0; I < Spellings.size(); ++ I) {
-      OS << "    if (Name == \"" << Spellings[I].name() << "\" && "
-         << "getSyntax() == AttributeCommonInfo::AS_" << Spellings[I].variety()
-         << " && Scope == \"" << Spellings[I].nameSpace() << "\")\n"
-         << "        return " << I << ";\n";
+
+    // If there are none or one spelling to check, resort to the default
+    // behavior of returning index as 0.
+    if (Spellings.size() <= 1) {
+      OS << "    return 0;\n"
+         << "    break;\n"
+         << "  }\n";
+      continue;
     }
 
-    OS << "    break;\n";
-    OS << "  }\n";
+    std::vector<StringRef> Names;
+    llvm::transform(Spellings, std::back_inserter(Names),
+                    [](const FlattenedSpelling &FS) { return FS.name(); });
+    llvm::sort(Names);
+    Names.erase(llvm::unique(Names), Names.end());
+
+    for (const auto &[Idx, FS] : enumerate(Spellings)) {
+      OS << "    if (";
+      if (Names.size() > 1) {
+        SmallVector<StringRef, 6> SameLenNames;
+        StringRef FSName = FS.name();
+        llvm::copy_if(Names, std::back_inserter(SameLenNames),
+                      [&](StringRef N) { return N.size() == FSName.size(); });
+
+        if (SameLenNames.size() == 1) {
+          OS << "Name.size() == " << FS.name().size() << " && ";
+        } else {
+          // FIXME: We currently fall back to comparing entire strings if there
+          // are 2 or more spelling names with the same length. This can be
+          // optimized to check only for the the first differing character
+          // between them instead.
+          OS << "Name == \"" << FS.name() << "\""
+             << " && ";
+        }
+      }
+
+      OS << "getSyntax() == AttributeCommonInfo::AS_" << FS.variety()
+         << " && ComputedScope == ";
+      if (FS.nameSpace() == "")
+        OS << "AttributeCommonInfo::Scope::NONE";
+      else
+        OS << "AttributeCommonInfo::Scope::" + FS.nameSpace().upper();
+
+      OS << ")\n"
+         << "      return " << Idx << ";\n";
+    }
+
+    OS << "    break;\n"
+       << "  }\n";
   }
 
-  OS << "  }\n";
-  OS << "  return 0;\n";
+  OS << "  }\n"
+     << "  return 0;\n";
 }
 
 // Emits code used by RecursiveASTVisitor to visit attributes