[Core] Skip over target name in intrinsic name lookup (#109971)

When searching for an intrinsic name in a target specific slice of the
intrinsic name table, skip over the target prefix. For such cases,
currently the first loop iteration in `lookupLLVMIntrinsicByName` does
nothing (i.e., `Low` and `High` stay unchanged and it does not shrink
down the search window), so we can skip this useless first iteration by
skipping over the target prefix.

Author: jurahul

llvm/include/llvm/IR/Intrinsics.h

@@ -95,7 +95,7 @@ namespace Intrinsic {
   /// match for Name or a prefix of Name followed by a dot, its index in
   /// NameTable is returned. Otherwise, -1 is returned.
   int lookupLLVMIntrinsicByName(ArrayRef<const char *> NameTable,
-                                StringRef Name);
+                                StringRef Name, StringRef Target = "");
 
   /// Map a Clang builtin name to an intrinsic ID.
   ID getIntrinsicForClangBuiltin(StringRef TargetPrefix, StringRef BuiltinName);

llvm/lib/IR/Function.cpp

@@ -940,8 +940,8 @@ void Function::setOnlyAccessesInaccessibleMemOrArgMem() {
 }
 
 /// Table of string intrinsic names indexed by enum value.
-static const char * const IntrinsicNameTable[] = {
-  "not_intrinsic",
+static constexpr const char *const IntrinsicNameTable[] = {
+    "not_intrinsic",
 #define GET_INTRINSIC_NAME_TABLE
 #include "llvm/IR/IntrinsicImpl.inc"
 #undef GET_INTRINSIC_NAME_TABLE
@@ -963,8 +963,9 @@ bool Function::isTargetIntrinsic() const {
 /// Find the segment of \c IntrinsicNameTable for intrinsics with the same
 /// target as \c Name, or the generic table if \c Name is not target specific.
 ///
-/// Returns the relevant slice of \c IntrinsicNameTable
-static ArrayRef<const char *> findTargetSubtable(StringRef Name) {
+/// Returns the relevant slice of \c IntrinsicNameTable and the target name.
+static std::pair<ArrayRef<const char *>, StringRef>
+findTargetSubtable(StringRef Name) {
   assert(Name.starts_with("llvm."));
 
   ArrayRef<IntrinsicTargetInfo> Targets(TargetInfos);
@@ -976,14 +977,14 @@ static ArrayRef<const char *> findTargetSubtable(StringRef Name) {
   // We've either found the target or just fall back to the generic set, which
   // is always first.
   const auto &TI = It != Targets.end() && It->Name == Target ? *It : Targets[0];
-  return ArrayRef(&IntrinsicNameTable[1] + TI.Offset, TI.Count);
+  return {ArrayRef(&IntrinsicNameTable[1] + TI.Offset, TI.Count), TI.Name};
 }
 
-/// This does the actual lookup of an intrinsic ID which
-/// matches the given function name.
+/// This does the actual lookup of an intrinsic ID which matches the given
+/// function name.
 Intrinsic::ID Function::lookupIntrinsicID(StringRef Name) {
-  ArrayRef<const char *> NameTable = findTargetSubtable(Name);
-  int Idx = Intrinsic::lookupLLVMIntrinsicByName(NameTable, Name);
+  auto [NameTable, Target] = findTargetSubtable(Name);
+  int Idx = Intrinsic::lookupLLVMIntrinsicByName(NameTable, Name, Target);
   if (Idx == -1)
     return Intrinsic::not_intrinsic;
 

llvm/lib/IR/IntrinsicInst.cpp

@@ -237,8 +237,10 @@ void DbgAssignIntrinsic::setValue(Value *V) {
 }
 
 int llvm::Intrinsic::lookupLLVMIntrinsicByName(ArrayRef<const char *> NameTable,
-                                               StringRef Name) {
+                                               StringRef Name,
+                                               StringRef Target) {
   assert(Name.starts_with("llvm.") && "Unexpected intrinsic prefix");
+  assert(Name.drop_front(5).starts_with(Target) && "Unexpected target");
 
   // Do successive binary searches of the dotted name components. For
   // "llvm.gc.experimental.statepoint.p1i8.p1i32", we will find the range of
@@ -248,6 +250,9 @@ int llvm::Intrinsic::lookupLLVMIntrinsicByName(ArrayRef<const char *> NameTable,
   // identical. By using strncmp we consider names with differing suffixes to
   // be part of the equal range.
   size_t CmpEnd = 4; // Skip the "llvm" component.
+  if (!Target.empty())
+    CmpEnd += 1 + Target.size(); // skip the .target component.
+
   const char *const *Low = NameTable.begin();
   const char *const *High = NameTable.end();
   const char *const *LastLow = Low;

llvm/lib/Transforms/Coroutines/Coroutines.cpp

@@ -97,7 +97,8 @@ static const char *const CoroIntrinsics[] = {
 
 #ifndef NDEBUG
 static bool isCoroutineIntrinsicName(StringRef Name) {
-  return Intrinsic::lookupLLVMIntrinsicByName(CoroIntrinsics, Name) != -1;
+  return Intrinsic::lookupLLVMIntrinsicByName(CoroIntrinsics, Name, "coro") !=
+         -1;
 }
 #endif
 

llvm/unittests/IR/IntrinsicsTest.cpp

@@ -31,10 +31,6 @@ using namespace llvm;
 
 namespace {
 
-static const char *const NameTable1[] = {
-    "llvm.foo", "llvm.foo.a", "llvm.foo.b", "llvm.foo.b.a", "llvm.foo.c",
-};
-
 class IntrinsicsTest : public ::testing::Test {
   LLVMContext Context;
   std::unique_ptr<Module> M;
@@ -67,18 +63,24 @@ class IntrinsicsTest : public ::testing::Test {
 };
 
 TEST(IntrinsicNameLookup, Basic) {
-  int I = Intrinsic::lookupLLVMIntrinsicByName(NameTable1, "llvm.foo");
-  EXPECT_EQ(0, I);
-  I = Intrinsic::lookupLLVMIntrinsicByName(NameTable1, "llvm.foo.f64");
-  EXPECT_EQ(0, I);
-  I = Intrinsic::lookupLLVMIntrinsicByName(NameTable1, "llvm.foo.b");
-  EXPECT_EQ(2, I);
-  I = Intrinsic::lookupLLVMIntrinsicByName(NameTable1, "llvm.foo.b.a");
-  EXPECT_EQ(3, I);
-  I = Intrinsic::lookupLLVMIntrinsicByName(NameTable1, "llvm.foo.c");
-  EXPECT_EQ(4, I);
-  I = Intrinsic::lookupLLVMIntrinsicByName(NameTable1, "llvm.foo.c.f64");
-  EXPECT_EQ(4, I);
+  static constexpr const char *const NameTable1[] = {
+      "llvm.foo", "llvm.foo.a", "llvm.foo.b", "llvm.foo.b.a", "llvm.foo.c",
+  };
+
+  static constexpr std::pair<const char *, int> Tests[] = {
+      {"llvm.foo", 0},     {"llvm.foo.f64", 0}, {"llvm.foo.b", 2},
+      {"llvm.foo.b.a", 3}, {"llvm.foo.c", 4},   {"llvm.foo.c.f64", 4},
+      {"llvm.bar", -1},
+  };
+
+  for (const auto &[Name, ExpectedIdx] : Tests) {
+    int Idx = Intrinsic::lookupLLVMIntrinsicByName(NameTable1, Name);
+    EXPECT_EQ(ExpectedIdx, Idx);
+    if (!StringRef(Name).starts_with("llvm.foo"))
+      continue;
+    Idx = Intrinsic::lookupLLVMIntrinsicByName(NameTable1, Name, "foo");
+    EXPECT_EQ(ExpectedIdx, Idx);
+  }
 }
 
 // Tests to verify getIntrinsicForClangBuiltin.