[llvm] Split out DenseMapInfo<variant> specialization

Remove the `DenseMapInfo<std::variant<Ts...>>` variant out from `llvm/ADT/DenseMapInfo.h` into a separate header `llvm/ADT/DenseMapInfoVariant.h` This allows us to remove the `<variant>` include, which is being transitively and unncessary included in all translation units that include `llvm/ADT/DenseMap.h`. There have been similar changes to move out specializations for * `APInt.h` fd7e309 and * `StringRef.h`/`ArrayRef.h` 983565a to reduce the compilation time. As we are unable to move the specialization into `<variant>`, we create a separate `DenseMapInfoVariant.h` header that can be used by anyone who needs this specialization. This reduces the total number of preprocessing tokens across the LLVM source files in lib from (roughly) 1,964,876,961 to 1,936,551,496 - a reduction of ~1.44%. This should result in a small improvement in compilation time. Differential Revision: https://reviews.llvm.org/D150997
llvm · Jun 22, 2023 · cea0eea · cea0eea
1 parent 791c3cb
commit cea0eea
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Showing 11 changed files with 90 additions and 47 deletions.
diff --git a/clang-tools-extra/include-cleaner/include/clang-include-cleaner/Types.h b/clang-tools-extra/include-cleaner/include/clang-include-cleaner/Types.h
@@ -26,10 +26,12 @@
 #include "clang/Tooling/Inclusions/StandardLibrary.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseMapInfoVariant.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
 #include <memory>
 #include <utility>
+#include <variant>
 #include <vector>
 
 namespace llvm {

diff --git a/flang/include/flang/Optimizer/HLFIR/HLFIROps.h b/flang/include/flang/Optimizer/HLFIR/HLFIROps.h
@@ -19,6 +19,7 @@
 #include "mlir/IR/PatternMatch.h"
 #include "mlir/Interfaces/InferTypeOpInterface.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
+#include <variant>
 
 #include "flang/Optimizer/HLFIR/HLFIROpInterfaces.h.inc"
 #define GET_OP_CLASSES

diff --git a/llvm/include/llvm/ADT/DenseMapInfo.h b/llvm/include/llvm/ADT/DenseMapInfo.h
@@ -20,7 +20,6 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-#include <variant>
 
 namespace llvm {
 
@@ -234,6 +233,14 @@ struct DenseMapInfo<std::pair<T, U>> {
                                     SecondInfo::getHashValue(PairVal.second));
   }
 
+  // Expose an additional function intended to be used by other
+  // specializations of DenseMapInfo without needing to know how
+  // to combine hash values manually
+  static unsigned getHashValuePiecewise(const T &First, const U &Second) {
+    return detail::combineHashValue(FirstInfo::getHashValue(First),
+                                    SecondInfo::getHashValue(Second));
+  }
+
   static bool isEqual(const Pair &LHS, const Pair &RHS) {
     return FirstInfo::isEqual(LHS.first, RHS.first) &&
            SecondInfo::isEqual(LHS.second, RHS.second);
@@ -290,52 +297,6 @@ template <typename... Ts> struct DenseMapInfo<std::tuple<Ts...>> {
   }
 };
 
-// Provide DenseMapInfo for variants whose all alternatives have DenseMapInfo.
-template <typename... Ts> struct DenseMapInfo<std::variant<Ts...>> {
-  using Variant = std::variant<Ts...>;
-  using FirstT = std::variant_alternative_t<0, Variant>;
-
-  static inline Variant getEmptyKey() {
-    return Variant(std::in_place_index<0>, DenseMapInfo<FirstT>::getEmptyKey());
-  }
-
-  static inline Variant getTombstoneKey() {
-    return Variant(std::in_place_index<0>,
-                   DenseMapInfo<FirstT>::getTombstoneKey());
-  }
-
-  static unsigned getHashValue(const Variant &Val) {
-    return std::visit(
-        [&Val](auto &&Alternative) {
-          using T = std::decay_t<decltype(Alternative)>;
-          // Include index in hash to make sure same value as different
-          // alternatives don't collide.
-          return detail::combineHashValue(
-              DenseMapInfo<size_t>::getHashValue(Val.index()),
-              DenseMapInfo<T>::getHashValue(Alternative));
-        },
-        Val);
-  }
-
-  static bool isEqual(const Variant &LHS, const Variant &RHS) {
-    if (LHS.index() != RHS.index())
-      return false;
-    if (LHS.valueless_by_exception())
-      return true;
-    // We want to dispatch to DenseMapInfo<T>::isEqual(LHS.get(I), RHS.get(I))
-    // We know the types are the same, but std::visit(V, LHS, RHS) doesn't.
-    // We erase the type held in LHS to void*, and dispatch over RHS.
-    const void *ErasedLHS =
-        std::visit([](const auto &LHS) -> const void * { return &LHS; }, LHS);
-    return std::visit(
-        [&](const auto &RHS) -> bool {
-          using T = std::remove_cv_t<std::remove_reference_t<decltype(RHS)>>;
-          return DenseMapInfo<T>::isEqual(*static_cast<const T *>(ErasedLHS),
-                                          RHS);
-        },
-        RHS);
-  }
-};
 } // end namespace llvm
 
 #endif // LLVM_ADT_DENSEMAPINFO_H
diff --git a/llvm/include/llvm/ADT/DenseMapInfoVariant.h b/llvm/include/llvm/ADT/DenseMapInfoVariant.h
@@ -0,0 +1,71 @@
+//===- DenseMapInfoVariant.h - Type traits for DenseMap<variant> *- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file defines DenseMapInfo traits for DenseMap<std::variant<Ts...>>.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_DENSEMAPINFOVARIANT_H
+#define LLVM_ADT_DENSEMAPINFOVARIANT_H
+
+#include "llvm/ADT/DenseMapInfo.h"
+#include <utility>
+#include <variant>
+
+namespace llvm {
+
+// Provide DenseMapInfo for variants whose all alternatives have DenseMapInfo.
+template <typename... Ts> struct DenseMapInfo<std::variant<Ts...>> {
+  using Variant = std::variant<Ts...>;
+  using FirstT = std::variant_alternative_t<0, Variant>;
+
+  static inline Variant getEmptyKey() {
+    return Variant(std::in_place_index<0>, DenseMapInfo<FirstT>::getEmptyKey());
+  }
+
+  static inline Variant getTombstoneKey() {
+    return Variant(std::in_place_index<0>,
+                   DenseMapInfo<FirstT>::getTombstoneKey());
+  }
+
+  static unsigned getHashValue(const Variant &Val) {
+    return std::visit(
+        [&Val](auto &&Alternative) {
+          using T = std::decay_t<decltype(Alternative)>;
+          // Include index in hash to make sure same value as different
+          // alternatives don't collide.
+          return DenseMapInfo<std::pair<size_t, T>>::getHashValuePiecewise(
+              Val.index(), Alternative);
+        },
+        Val);
+  }
+
+  static bool isEqual(const Variant &LHS, const Variant &RHS) {
+    if (LHS.index() != RHS.index())
+      return false;
+    if (LHS.valueless_by_exception())
+      return true;
+    // We want to dispatch to DenseMapInfo<T>::isEqual(LHS.get(I), RHS.get(I))
+    // We know the types are the same, but std::visit(V, LHS, RHS) doesn't.
+    // We erase the type held in LHS to void*, and dispatch over RHS.
+    const void *ErasedLHS =
+        std::visit([](const auto &LHS) -> const void * { return &LHS; }, LHS);
+    return std::visit(
+        [&](const auto &RHS) -> bool {
+          using T = std::remove_cv_t<std::remove_reference_t<decltype(RHS)>>;
+          return DenseMapInfo<T>::isEqual(*static_cast<const T *>(ErasedLHS),
+                                          RHS);
+        },
+        RHS);
+  }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_DENSEMAPINFOVARIANT_H
diff --git a/llvm/include/llvm/CodeGen/CallingConvLower.h b/llvm/include/llvm/CodeGen/CallingConvLower.h
@@ -19,6 +19,8 @@
 #include "llvm/CodeGen/TargetCallingConv.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/Support/Alignment.h"
+#include <variant>
+#include <vector>
 
 namespace llvm {
 

diff --git a/llvm/include/llvm/ExecutionEngine/Orc/LLJIT.h b/llvm/include/llvm/ExecutionEngine/Orc/LLJIT.h
@@ -22,6 +22,7 @@
 #include "llvm/ExecutionEngine/Orc/ThreadSafeModule.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ThreadPool.h"
+#include <variant>
 
 namespace llvm {
 namespace orc {

diff --git a/llvm/include/llvm/Object/DXContainer.h b/llvm/include/llvm/Object/DXContainer.h
@@ -21,6 +21,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MemoryBufferRef.h"
 #include "llvm/TargetParser/Triple.h"
+#include <variant>
 
 namespace llvm {
 namespace object {

diff --git a/llvm/include/llvm/Transforms/Scalar/SROA.h b/llvm/include/llvm/Transforms/Scalar/SROA.h
@@ -21,6 +21,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/ValueHandle.h"
+#include <variant>
 #include <vector>
 
 namespace llvm {

diff --git a/llvm/unittests/ADT/DenseMapTest.cpp b/llvm/unittests/ADT/DenseMapTest.cpp
@@ -8,6 +8,7 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/DenseMapInfoVariant.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <map>

diff --git a/mlir/include/mlir/IR/AsmState.h b/mlir/include/mlir/IR/AsmState.h
@@ -20,6 +20,7 @@
 #include "llvm/ADT/StringMap.h"
 
 #include <memory>
+#include <variant>
 
 namespace mlir {
 class AsmResourcePrinter;

diff --git a/mlir/include/mlir/Transforms/SROA.h b/mlir/include/mlir/Transforms/SROA.h
@@ -13,6 +13,7 @@
 #include "mlir/Interfaces/MemorySlotInterfaces.h"
 #include "mlir/Support/LogicalResult.h"
 #include "llvm/ADT/Statistic.h"
+#include <variant>
 
 namespace mlir {