Canonicalize away bit width and embed small integers into IntIds

toolchain/base/BUILD

@@ -47,6 +47,7 @@ cc_library(
     hdrs = ["value_ids.h"],
     deps = [
         ":index_base",
+        "//common:check",
         "//common:ostream",
         "@llvm-project//llvm:Support",
     ],
@@ -80,10 +81,41 @@ cc_test(
     ],
 )
 
+cc_library(
+    name = "int_store",
+    srcs = ["int_store.cpp"],
+    hdrs = ["int_store.h"],
+    deps = [
+        ":index_base",
+        ":mem_usage",
+        ":value_store",
+        ":yaml",
+        "//common:check",
+        "//common:hashtable_key_context",
+        "//common:ostream",
+        "//common:set",
+        "@llvm-project//llvm:Support",
+    ],
+)
+
+cc_test(
+    name = "int_store_test",
+    size = "small",
+    srcs = ["int_store_test.cpp"],
+    deps = [
+        ":int_store",
+        "//testing/base:gtest_main",
+        "//testing/base:test_raw_ostream",
+        "//toolchain/testing:yaml_test_helpers",
+        "@googletest//:gtest",
+    ],
+)
+
 cc_library(
     name = "shared_value_stores",
     hdrs = ["shared_value_stores.h"],
     deps = [
+        ":int_store",
         ":mem_usage",
         ":value_ids",
         ":value_store",

toolchain/base/int_store.cpp

@@ -0,0 +1,66 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include "toolchain/base/int_store.h"
+
+namespace Carbon {
+
+auto IntStore::CanonicalBitWidth(int significant_bits) -> int {
+  // For larger integers, we store them in as a signed APInt with a canonical
+  // width that is the smallest multiple of the word type's bits, but no
+  // smaller than a minimum of 64 bits to avoid spurious resizing of the most
+  // common cases (<= 64 bits).
+  static constexpr int WordWidth = llvm::APInt::APINT_BITS_PER_WORD;
+
+  return std::max<int>(
+      MinAPWidth, ((significant_bits + WordWidth - 1) / WordWidth) * WordWidth);
+}
+
+auto IntStore::CanonicalizeSigned(llvm::APInt value) -> llvm::APInt {
+  return value.sextOrTrunc(CanonicalBitWidth(value.getSignificantBits()));
+}
+
+auto IntStore::CanonicalizeUnsigned(llvm::APInt value) -> llvm::APInt {
+  // We need the width to include a zero sign bit as we canonicalize to a
+  // signed representation.
+  return value.zextOrTrunc(CanonicalBitWidth(value.getActiveBits() + 1));
+}
+
+auto IntStore::AddLarge(int64_t value) -> IntId {
+  auto ap_id =
+      values_.Add(llvm::APInt(CanonicalBitWidth(64), value, /*isSigned=*/true));
+  return MakeIndexOrInvalid(ap_id.index);
+}
+
+auto IntStore::AddSignedLarge(llvm::APInt value) -> IntId {
+  auto ap_id = values_.Add(CanonicalizeSigned(value));
+  return MakeIndexOrInvalid(ap_id.index);
+}
+
+auto IntStore::AddUnsignedLarge(llvm::APInt value) -> IntId {
+  auto ap_id = values_.Add(CanonicalizeUnsigned(value));
+  return MakeIndexOrInvalid(ap_id.index);
+}
+
+auto IntStore::LookupLarge(int64_t value) const -> IntId {
+  auto ap_id = values_.Lookup(
+      llvm::APInt(CanonicalBitWidth(64), value, /*isSigned=*/true));
+  return MakeIndexOrInvalid(ap_id.index);
+}
+
+auto IntStore::LookupSignedLarge(llvm::APInt value) const -> IntId {
+  auto ap_id = values_.Lookup(CanonicalizeSigned(value));
+  return MakeIndexOrInvalid(ap_id.index);
+}
+
+auto IntStore::OutputYaml() const -> Yaml::OutputMapping {
+  return values_.OutputYaml();
+}
+
+auto IntStore::CollectMemUsage(MemUsage& mem_usage, llvm::StringRef label) const
+    -> void {
+  mem_usage.Collect(std::string(label), values_);
+}
+
+}  // namespace Carbon