[TableGen] Rework EmitIntrinsicToBuiltinMap (#104681)

Rework `IntrinsicEmitter::EmitIntrinsicToBuiltinMap` for improved
    peformance as well as refactor the code.

    Performance:
    - Current generated code does a linear search on the TargetPrefix,
      followed by a binary search on the builtin names for that
      target's builtins.
    - Improve the performance of this code in 2 ways:
      (a) Use binary search on the target prefix to lookup the builtin
          table for the target.
      (b) Improve the (common) case of when all builtins for a target
          share a common prefix.  Check this common prefix first, and
then do the binary search in the builtin table using the builtin
          name with the common prefix removed. This should help
          both data size (by creating a smaller static string table) and
          runtime (by reducing the cost of binary search on smaller
          strings).

    Refactor:
    - Use range based for loops for iterating over maps.
- Use formatv() and C++ raw string literals to simplify the emission
code.
    - Change the generated `getIntrinsicForClangBuiltin` and 
      `getIntrinsicForMSBuiltin`  to take a `StringRef` instead of 
      `const char *` for the prefix.

Author: jurahul

llvm/benchmarks/CMakeLists.txt

@@ -1,5 +1,7 @@
 set(LLVM_LINK_COMPONENTS
+  Core
   Support)
 
 add_benchmark(DummyYAML DummyYAML.cpp PARTIAL_SOURCES_INTENDED)
 add_benchmark(xxhash xxhash.cpp PARTIAL_SOURCES_INTENDED)
+add_benchmark(GetIntrinsicForClangBuiltin GetIntrinsicForClangBuiltin.cpp PARTIAL_SOURCES_INTENDED)

llvm/benchmarks/GetIntrinsicForClangBuiltin.cpp

@@ -0,0 +1,50 @@
+#include "benchmark/benchmark.h"
+#include "llvm/IR/Intrinsics.h"
+
+using namespace llvm;
+using namespace Intrinsic;
+
+// Benchmark intrinsic lookup from a variety of targets.
+static void BM_GetIntrinsicForClangBuiltin(benchmark::State &state) {
+  static const char *Builtins[] = {
+      "__builtin_adjust_trampoline",
+      "__builtin_trap",
+      "__builtin_arm_ttest",
+      "__builtin_amdgcn_cubetc",
+      "__builtin_amdgcn_udot2",
+      "__builtin_arm_stc",
+      "__builtin_bpf_compare",
+      "__builtin_HEXAGON_A2_max",
+      "__builtin_lasx_xvabsd_b",
+      "__builtin_mips_dlsa",
+      "__nvvm_floor_f",
+      "__builtin_altivec_vslb",
+      "__builtin_r600_read_tgid_x",
+      "__builtin_riscv_aes64im",
+      "__builtin_s390_vcksm",
+      "__builtin_ve_vl_pvfmksge_Mvl",
+      "__builtin_ia32_axor64",
+      "__builtin_bitrev",
+  };
+  static const char *Targets[] = {"",     "aarch64", "amdgcn", "mips",
+                                  "nvvm", "r600",    "riscv"};
+
+  for (auto _ : state) {
+    for (auto Builtin : Builtins)
+      for (auto Target : Targets)
+        getIntrinsicForClangBuiltin(Target, Builtin);
+  }
+}
+
+static void
+BM_GetIntrinsicForClangBuiltinHexagonFirst(benchmark::State &state) {
+  // Exercise the worst case by looking for the first builtin for a target
+  // that has a lot of builtins.
+  for (auto _ : state)
+    getIntrinsicForClangBuiltin("hexagon", "__builtin_HEXAGON_A2_abs");
+}
+
+BENCHMARK(BM_GetIntrinsicForClangBuiltin);
+BENCHMARK(BM_GetIntrinsicForClangBuiltinHexagonFirst);
+
+BENCHMARK_MAIN();

llvm/include/llvm/IR/Intrinsics.h

@@ -100,10 +100,10 @@ namespace Intrinsic {
                                 StringRef Name);
 
   /// Map a Clang builtin name to an intrinsic ID.
-  ID getIntrinsicForClangBuiltin(const char *Prefix, StringRef BuiltinName);
+  ID getIntrinsicForClangBuiltin(StringRef TargetPrefix, StringRef BuiltinName);
 
   /// Map a MS builtin name to an intrinsic ID.
-  ID getIntrinsicForMSBuiltin(const char *Prefix, StringRef BuiltinName);
+  ID getIntrinsicForMSBuiltin(StringRef TargetPrefix, StringRef BuiltinName);
 
   /// Returns true if the intrinsic ID is for one of the "Constrained
   /// Floating-Point Intrinsics".

llvm/include/llvm/TableGen/StringToOffsetTable.h

@@ -14,6 +14,7 @@
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cctype>
+#include <optional>
 
 namespace llvm {
 
@@ -26,7 +27,8 @@ class StringToOffsetTable {
   std::string AggregateString;
 
 public:
-  bool Empty() const { return StringOffset.empty(); }
+  bool empty() const { return StringOffset.empty(); }
+  size_t size() const { return AggregateString.size(); }
 
   unsigned GetOrAddStringOffset(StringRef Str, bool appendZero = true) {
     auto IterBool =
@@ -41,6 +43,15 @@ class StringToOffsetTable {
     return IterBool.first->second;
   }
 
+  // Returns the offset of `Str` in the table if its preset, else return
+  // std::nullopt.
+  std::optional<unsigned> GetStringOffset(StringRef Str) const {
+    auto II = StringOffset.find(Str);
+    if (II == StringOffset.end())
+      return std::nullopt;
+    return II->second;
+  }
+
   void EmitString(raw_ostream &O) {
     // Escape the string.
     SmallString<256> Str;

llvm/unittests/IR/IntrinsicsTest.cpp

@@ -11,6 +11,19 @@
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/IntrinsicsAArch64.h"
+#include "llvm/IR/IntrinsicsAMDGPU.h"
+#include "llvm/IR/IntrinsicsARM.h"
+#include "llvm/IR/IntrinsicsBPF.h"
+#include "llvm/IR/IntrinsicsDirectX.h"
+#include "llvm/IR/IntrinsicsHexagon.h"
+#include "llvm/IR/IntrinsicsLoongArch.h"
+#include "llvm/IR/IntrinsicsMips.h"
+#include "llvm/IR/IntrinsicsNVPTX.h"
+#include "llvm/IR/IntrinsicsPowerPC.h"
+#include "llvm/IR/IntrinsicsRISCV.h"
+#include "llvm/IR/IntrinsicsS390.h"
+#include "llvm/IR/IntrinsicsX86.h"
 #include "llvm/IR/Module.h"
 #include "gtest/gtest.h"
 
@@ -68,6 +81,51 @@ TEST(IntrinsicNameLookup, Basic) {
   EXPECT_EQ(4, I);
 }
 
+// Tests to verify getIntrinsicForClangBuiltin.
+TEST(IntrinsicNameLookup, ClangBuiltinLookup) {
+  using namespace Intrinsic;
+  static constexpr std::tuple<StringRef, StringRef, ID> ClangTests[] = {
+      {"__builtin_adjust_trampoline", "", adjust_trampoline},
+      {"__builtin_trap", "", trap},
+      {"__builtin_arm_chkfeat", "aarch64", aarch64_chkfeat},
+      {"__builtin_amdgcn_alignbyte", "amdgcn", amdgcn_alignbyte},
+      {"__builtin_amdgcn_workgroup_id_z", "amdgcn", amdgcn_workgroup_id_z},
+      {"__builtin_arm_cdp", "arm", arm_cdp},
+      {"__builtin_bpf_preserve_type_info", "bpf", bpf_preserve_type_info},
+      {"__builtin_hlsl_create_handle", "dx", dx_create_handle},
+      {"__builtin_HEXAGON_A2_tfr", "hexagon", hexagon_A2_tfr},
+      {"__builtin_lasx_xbz_w", "loongarch", loongarch_lasx_xbz_w},
+      {"__builtin_mips_bitrev", "mips", mips_bitrev},
+      {"__nvvm_add_rn_d", "nvvm", nvvm_add_rn_d},
+      {"__builtin_altivec_dss", "ppc", ppc_altivec_dss},
+      {"__builtin_riscv_sha512sum1r", "riscv", riscv_sha512sum1r},
+      {"__builtin_tend", "s390", s390_tend},
+      {"__builtin_ia32_pause", "x86", x86_sse2_pause},
+
+      {"__does_not_exist", "", not_intrinsic},
+      {"__does_not_exist", "arm", not_intrinsic},
+      {"__builtin_arm_cdp", "", not_intrinsic},
+      {"__builtin_arm_cdp", "x86", not_intrinsic},
+  };
+
+  for (const auto &[Builtin, Target, ID] : ClangTests)
+    EXPECT_EQ(ID, getIntrinsicForClangBuiltin(Target, Builtin));
+}
+
+// Tests to verify getIntrinsicForMSBuiltin.
+TEST(IntrinsicNameLookup, MSBuiltinLookup) {
+  using namespace Intrinsic;
+  static constexpr std::tuple<StringRef, StringRef, ID> MSTests[] = {
+      {"__dmb", "aarch64", aarch64_dmb},
+      {"__dmb", "arm", arm_dmb},
+      {"__dmb", "", not_intrinsic},
+      {"__does_not_exist", "", not_intrinsic},
+      {"__does_not_exist", "arm", not_intrinsic},
+  };
+  for (const auto &[Builtin, Target, ID] : MSTests)
+    EXPECT_EQ(ID, getIntrinsicForMSBuiltin(Target, Builtin));
+}
+
 TEST_F(IntrinsicsTest, InstrProfInheritance) {
   auto isInstrProfInstBase = [](const Instruction &I) {
     return isa<InstrProfInstBase>(I);
@@ -106,4 +164,5 @@ TEST_F(IntrinsicsTest, InstrProfInheritance) {
     EXPECT_TRUE(Checker(*Intr));
   }
 }
+
 } // end namespace