[StrTable] Add prefixes for x86 builtins.

This requires adding support to the general builtins emission for
producing prefixed builtin infos separately from un-prefixed which is
a bit crufty. But we don't currently have any good way of having a more
refined model than a single hard-coded prefix string per TableGen
emission. Something more powerful and/or elegant is possible, but this
is a fairly minimal first step that at least allows factoring out the
builtin prefix for something like X86.

clang/include/clang/Basic/BuiltinsBase.td

@@ -86,6 +86,13 @@ def Consteval : Attribute<"EG">;
 // indicated by the remaining indices.
 class Callback<list<int> ArgIndices> : MultiIndexAttribute<"C", ArgIndices>;
 
+// Prefixes
+// ========
+
+class NamePrefix<string spelling> {
+  string Spelling = spelling;
+}
+
 // Builtin kinds
 // =============
 
@@ -99,6 +106,9 @@ class Builtin {
   bit RequiresUndef = 0;
   // Enables builtins to generate `long long` outside of OpenCL and `long` inside.
   bit EnableOpenCLLong = 0;
+  // Requires a common prefix to be prepended. Each generated set of builtins
+  // can optionally extract one common prefix that is handled separately.
+  NamePrefix RequiredNamePrefix;
 }
 
 class AtomicBuiltin : Builtin;

clang/include/clang/Basic/BuiltinsX86Base.td

@@ -12,10 +12,13 @@
 
 include "clang/Basic/BuiltinsBase.td"
 
+def X86Prefix : NamePrefix<"__builtin_ia32_">;
+
 class X86Builtin<string prototype> : TargetBuiltin {
-  let Spellings = ["__builtin_ia32_" # NAME];
+  let Spellings = [NAME];
   let Prototype = prototype;
   let EnableOpenCLLong = 1;
+  let RequiredNamePrefix = X86Prefix; // Adds a prefix to the name.
 }
 
 class X86NoPrefixBuiltin<string prototype> : TargetBuiltin {

clang/lib/Basic/Targets/X86.cpp

@@ -41,7 +41,14 @@ static constexpr Builtin::Info BuiltinInfos[] = {
 #include "clang/Basic/BuiltinsX86.inc"
 #undef GET_BUILTIN_INFOS
 };
-static_assert(std::size(BuiltinInfos) == NumX86Builtins);
+
+static constexpr Builtin::Info PrefixedBuiltinInfos[] = {
+#define GET_BUILTIN_PREFIXED_INFOS
+#include "clang/Basic/BuiltinsX86.inc"
+#undef GET_BUILTIN_PREFIXED_INFOS
+};
+static_assert((std::size(BuiltinInfos) + std::size(PrefixedBuiltinInfos)) ==
+              NumX86Builtins);
 } // namespace X86
 
 namespace X86_64 {
@@ -54,7 +61,14 @@ static constexpr Builtin::Info BuiltinInfos[] = {
 #include "clang/Basic/BuiltinsX86_64.inc"
 #undef GET_BUILTIN_INFOS
 };
-static_assert(std::size(BuiltinInfos) == NumX86_64Builtins);
+
+static constexpr Builtin::Info PrefixedBuiltinInfos[] = {
+#define GET_BUILTIN_PREFIXED_INFOS
+#include "clang/Basic/BuiltinsX86_64.inc"
+#undef GET_BUILTIN_PREFIXED_INFOS
+};
+static_assert((std::size(BuiltinInfos) + std::size(PrefixedBuiltinInfos)) ==
+              NumX86_64Builtins);
 } // namespace X86_64
 
 static const char *const GCCRegNames[] = {
@@ -1874,13 +1888,19 @@ ArrayRef<TargetInfo::AddlRegName> X86TargetInfo::getGCCAddlRegNames() const {
 
 llvm::SmallVector<Builtin::InfosShard>
 X86_32TargetInfo::getTargetBuiltins() const {
-  return {{&X86::BuiltinStrings, X86::BuiltinInfos}};
+  return {
+      {&X86::BuiltinStrings, X86::BuiltinInfos},
+      {&X86::BuiltinStrings, X86::PrefixedBuiltinInfos, "__builtin_ia32_"},
+  };
 }
 
 llvm::SmallVector<Builtin::InfosShard>
 X86_64TargetInfo::getTargetBuiltins() const {
   return {
       {&X86::BuiltinStrings, X86::BuiltinInfos},
+      {&X86::BuiltinStrings, X86::PrefixedBuiltinInfos, "__builtin_ia32_"},
       {&X86_64::BuiltinStrings, X86_64::BuiltinInfos},
+      {&X86_64::BuiltinStrings, X86_64::PrefixedBuiltinInfos,
+       "__builtin_ia32_"},
   };
 }

clang/utils/TableGen/ClangBuiltinsEmitter.cpp

@@ -59,7 +59,13 @@ struct Builtin {
   const Record *BuiltinRecord;
 
   void EmitEnumerator(llvm::raw_ostream &OS) const {
-    OS << "    BI" << Name << ",\n";
+    OS << "    BI";
+    // If there is a required name prefix, include its spelling in the
+    // enumerator.
+    if (auto *PrefixRecord =
+            BuiltinRecord->getValueAsOptionalDef("RequiredNamePrefix"))
+      OS << PrefixRecord->getValueAsString("Spelling");
+    OS << Name << ",\n";
   }
 
   void EmitInfo(llvm::raw_ostream &OS, const StringToOffsetTable &Table) const {
@@ -482,17 +488,42 @@ void clang::EmitClangBuiltins(const RecordKeeper &Records, raw_ostream &OS) {
   for (const auto *BuiltinRecord :
        Records.getAllDerivedDefinitions("AtomicBuiltin"))
     collectBuiltins(BuiltinRecord, Builtins);
-
   unsigned NumAtomicBuiltins = Builtins.size();
 
   for (const auto *BuiltinRecord :
        Records.getAllDerivedDefinitions("Builtin")) {
     if (BuiltinRecord->isSubClassOf("AtomicBuiltin"))
       continue;
+    // Prefixed builtins are also special and we emit them last so they can have
+    // their own representation that skips the prefix.
+    if (BuiltinRecord->getValueAsOptionalDef("RequiredNamePrefix"))
+      continue;
+
     collectBuiltins(BuiltinRecord, Builtins);
   }
 
+  // Now collect (and count) the prefixed builtins.
+  unsigned NumPrefixedBuiltins = Builtins.size();
+  const Record *FirstPrefix = nullptr;
+  for (const auto *BuiltinRecord :
+       Records.getAllDerivedDefinitions("Builtin")) {
+    auto *Prefix = BuiltinRecord->getValueAsOptionalDef("RequiredNamePrefix");
+    if (!Prefix)
+      continue;
+
+    if (!FirstPrefix)
+      FirstPrefix = Prefix;
+    assert(Prefix == FirstPrefix &&
+           "Multiple distinct prefixes which is not currently supported!");
+    assert(!BuiltinRecord->isSubClassOf("AtomicBuiltin") &&
+           "Cannot require a name prefix for an atomic builtin.");
+    collectBuiltins(BuiltinRecord, Builtins);
+  }
+  NumPrefixedBuiltins = Builtins.size() - NumPrefixedBuiltins;
+
   auto AtomicBuiltins = ArrayRef(Builtins).slice(0, NumAtomicBuiltins);
+  auto UnprefixedBuiltins = ArrayRef(Builtins).drop_back(NumPrefixedBuiltins);
+  auto PrefixedBuiltins = ArrayRef(Builtins).take_back(NumPrefixedBuiltins);
 
   // Collect strings into a table.
   StringToOffsetTable Table;
@@ -524,14 +555,24 @@ void clang::EmitClangBuiltins(const RecordKeeper &Records, raw_ostream &OS) {
 #endif // GET_BUILTIN_STR_TABLE
 )c++";
 
-  // Emit a direct set of `Builtin::Info` initializers.
+  // Emit a direct set of `Builtin::Info` initializers, first for the unprefixed
+  // builtins and then for the prefixed builtins.
   OS << R"c++(
 #ifdef GET_BUILTIN_INFOS
 )c++";
-  for (const auto &B : Builtins)
+  for (const auto &B : UnprefixedBuiltins)
     B.EmitInfo(OS, Table);
   OS << R"c++(
 #endif // GET_BUILTIN_INFOS
+)c++";
+
+  OS << R"c++(
+#ifdef GET_BUILTIN_PREFIXED_INFOS
+)c++";
+  for (const auto &B : PrefixedBuiltins)
+    B.EmitInfo(OS, Table);
+  OS << R"c++(
+#endif // GET_BUILTIN_PREFIXED_INFOS
 )c++";
 
   // Emit X-macros for the atomic builtins to support various custome patterns