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Key context improvements (#4095)
This injects a customization point for hashtable-specific equality testing that the key context uses by default. While this is rarely needed, there are LLVM types where it is necessary and it seems a good general tool to have to avoid unnecessary complexity from custom key contexts when a simple customization of equality is all that is required. This also adds a CRTP mixin for implementing a common pattern of key contexts where the context provides translation of some key types into another type, potentially using state. Rather than having to implement the entire key context API, code can derive from this template and simply provide a set of overloads for the types it wants to translate. Any key types used which can be passed to one of those overloads will get translated before following the same logic as the default key context. While this updates the only usage so far of this pattern, a subsequent PR will add several more users making the pattern worth abstracting here.
This commit is contained in:
Chandler Carruth
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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "common/hashtable_key_context.h"
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#include <gmock/gmock.h>
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#include <gtest/gtest.h>
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namespace Carbon {
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namespace {
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using ::testing::Eq;
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using ::testing::Ne;
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struct DefaultEq {
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int x, y;
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friend auto operator==(const DefaultEq& lhs, const DefaultEq& rhs)
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-> bool = default;
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};
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struct CustomEq {
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int x, y;
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friend auto operator==(const CustomEq& lhs, const CustomEq& rhs) -> bool {
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return lhs.x == rhs.x && lhs.y == rhs.y;
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}
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};
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struct CustomExtEq {
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int x, y;
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friend auto CarbonHashtableEq(const CustomExtEq& lhs, const CustomExtEq& rhs)
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-> bool {
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return lhs.x == rhs.x && lhs.y == rhs.y;
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}
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};
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TEST(HashtableKeyContextTest, HashtableEq) {
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EXPECT_TRUE(HashtableEq(0, 0));
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EXPECT_FALSE(HashtableEq(1, 0));
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EXPECT_FALSE(HashtableEq(0, 1));
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EXPECT_FALSE(HashtableEq(1234, 5678));
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EXPECT_TRUE(HashtableEq(5678, 5678));
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EXPECT_TRUE(
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HashtableEq(DefaultEq{.x = 0, .y = 0}, DefaultEq{.x = 0, .y = 0}));
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EXPECT_FALSE(
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HashtableEq(DefaultEq{.x = 1, .y = 2}, DefaultEq{.x = 3, .y = 4}));
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EXPECT_TRUE(HashtableEq(CustomEq{.x = 0, .y = 0}, CustomEq{.x = 0, .y = 0}));
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EXPECT_FALSE(HashtableEq(CustomEq{.x = 1, .y = 2}, CustomEq{.x = 3, .y = 4}));
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EXPECT_TRUE(
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HashtableEq(CustomExtEq{.x = 0, .y = 0}, CustomExtEq{.x = 0, .y = 0}));
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EXPECT_FALSE(
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HashtableEq(CustomExtEq{.x = 1, .y = 2}, CustomExtEq{.x = 3, .y = 4}));
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}
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TEST(HashtableKeyContextTest, HashtableEqAPInt) {
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// Hashtable equality doesn't assert on mismatched bit width, it includes the
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// bit width in the comparison.
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llvm::APInt one_64(/*numBits=*/64, /*val=*/1);
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llvm::APInt two_64(/*numBits=*/64, /*val=*/2);
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llvm::APInt one_128(/*numBits=*/128, /*val=*/1);
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llvm::APInt two_128(/*numBits=*/128, /*val=*/2);
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EXPECT_TRUE(HashtableEq(one_64, one_64));
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EXPECT_FALSE(HashtableEq(one_64, one_128));
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EXPECT_TRUE(HashtableEq(two_128, two_128));
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EXPECT_FALSE(HashtableEq(two_64, two_128));
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EXPECT_FALSE(HashtableEq(one_64, two_64));
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EXPECT_FALSE(HashtableEq(one_64, two_128));
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EXPECT_FALSE(HashtableEq(one_128, two_128));
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EXPECT_FALSE(HashtableEq(one_128, two_64));
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}
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TEST(HashtableKeyContextTest, HashtableEqAPFloat) {
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// Hashtable equality for `APFloat` uses a bitwise comparison. This
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// differentiates between various things that would otherwise not make sense:
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// - Different floating point semantics
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// - `-0.0` and `0.0`
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//
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// It also allows NaNs to be compared meaningfully.
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llvm::APFloat zero_float =
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llvm::APFloat::getZero(llvm::APFloat::IEEEsingle());
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llvm::APFloat neg_zero_float =
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llvm::APFloat::getZero(llvm::APFloat::IEEEsingle(), /*Negative=*/true);
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llvm::APFloat zero_double =
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llvm::APFloat::getZero(llvm::APFloat::IEEEdouble());
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llvm::APFloat zero_bfloat = llvm::APFloat::getZero(llvm::APFloat::BFloat());
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llvm::APFloat one_float = llvm::APFloat::getOne(llvm::APFloat::IEEEsingle());
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llvm::APFloat inf_float = llvm::APFloat::getInf(llvm::APFloat::IEEEsingle());
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llvm::APFloat nan_0_float = llvm::APFloat::getNaN(
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llvm::APFloat::IEEEsingle(), /*Negative=*/false, /*payload=*/0);
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llvm::APFloat nan_42_float = llvm::APFloat::getNaN(
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llvm::APFloat::IEEEsingle(), /*Negative=*/false, /*payload=*/42);
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// Boring cases.
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EXPECT_TRUE(HashtableEq(zero_float, zero_float));
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EXPECT_FALSE(HashtableEq(zero_float, one_float));
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EXPECT_TRUE(HashtableEq(inf_float, inf_float));
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EXPECT_FALSE(HashtableEq(inf_float, one_float));
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// Confirm a case where we expect `==` to work but produce a different result.
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ASSERT_TRUE(zero_float == neg_zero_float);
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EXPECT_FALSE(HashtableEq(zero_float, neg_zero_float));
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// Now work through less reasonable things outside of a hashtable such as
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// mixing semantics and NaNs.
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EXPECT_FALSE(HashtableEq(zero_float, zero_double));
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EXPECT_FALSE(HashtableEq(zero_float, zero_bfloat));
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EXPECT_FALSE(HashtableEq(zero_float, nan_0_float));
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EXPECT_FALSE(HashtableEq(zero_float, nan_42_float));
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EXPECT_FALSE(HashtableEq(nan_0_float, nan_42_float));
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}
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struct CustomHash {
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int x;
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friend auto CarbonHashValue(const CustomHash& value, uint64_t seed)
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-> HashCode {
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return HashValue(value.x + 42, seed);
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}
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};
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TEST(HashtableKeyContextTest, DefaultKeyContext) {
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// Make sure the default context dispatches appropriately, including for
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// interesting types. We don't cover all the cases here and use the direct
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// tests of `HashtableEq` for that.
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DefaultKeyContext context;
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EXPECT_FALSE(context.KeyEq(1234, 5678));
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EXPECT_TRUE(context.KeyEq(5678, 5678));
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EXPECT_TRUE(context.KeyEq(DefaultEq{0, 0}, DefaultEq{0, 0}));
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EXPECT_FALSE(context.KeyEq(DefaultEq{1, 2}, DefaultEq{3, 4}));
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EXPECT_TRUE(context.KeyEq(CustomEq{0, 0}, CustomEq{0, 0}));
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EXPECT_FALSE(context.KeyEq(CustomEq{1, 2}, CustomEq{3, 4}));
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EXPECT_TRUE(context.KeyEq(CustomExtEq{0, 0}, CustomExtEq{0, 0}));
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EXPECT_FALSE(context.KeyEq(CustomExtEq{1, 2}, CustomExtEq{3, 4}));
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llvm::APInt one_64(/*numBits=*/64, /*val=*/1);
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llvm::APInt one_128(/*numBits=*/128, /*val=*/1);
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EXPECT_TRUE(HashtableEq(one_64, one_64));
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EXPECT_FALSE(HashtableEq(one_64, one_128));
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llvm::APFloat zero_float =
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llvm::APFloat::getZero(llvm::APFloat::IEEEsingle());
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llvm::APFloat neg_zero_float =
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llvm::APFloat::getZero(llvm::APFloat::IEEEsingle(), /*Negative=*/true);
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EXPECT_TRUE(HashtableEq(zero_float, zero_float));
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EXPECT_FALSE(HashtableEq(zero_float, neg_zero_float));
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// Also check hash dispatching.
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uint64_t seed = 1234;
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EXPECT_THAT(context.HashKey(42, seed), Eq(HashValue(42, seed)));
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EXPECT_THAT(context.HashKey(CustomHash{.x = 1234}, seed),
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Eq(HashValue(CustomHash{.x = 1234}, seed)));
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EXPECT_THAT(context.HashKey(one_64, seed), Eq(HashValue(one_64, seed)));
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EXPECT_THAT(context.HashKey(one_128, seed), Eq(HashValue(one_128, seed)));
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EXPECT_THAT(context.HashKey(one_64, seed),
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Ne(context.HashKey(one_128, seed)));
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EXPECT_THAT(context.HashKey(zero_float, seed),
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Eq(HashValue(zero_float, seed)));
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EXPECT_THAT(context.HashKey(neg_zero_float, seed),
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Eq(HashValue(neg_zero_float, seed)));
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EXPECT_THAT(context.HashKey(zero_float, seed),
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Ne(context.HashKey(neg_zero_float, seed)));
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}
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struct TestTranslatingKeyContext
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: TranslatingKeyContext<TestTranslatingKeyContext> {
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auto TranslateKey(int index) const -> const llvm::APInt& {
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return array[index];
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}
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llvm::ArrayRef<llvm::APInt> array;
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};
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TEST(HashtableKeyContextTest, TranslatingKeyContext) {
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llvm::APInt one_64(/*numBits=*/64, /*val=*/1);
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llvm::APInt two_64(/*numBits=*/64, /*val=*/2);
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llvm::APInt one_128(/*numBits=*/128, /*val=*/1);
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llvm::APInt two_128(/*numBits=*/128, /*val=*/2);
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// An array of values, including some duplicates.
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llvm::SmallVector<llvm::APInt> values = {one_64, two_64, one_128,
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two_128, one_64, one_64};
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TestTranslatingKeyContext context = {.array = values};
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uint64_t seed = 1234;
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EXPECT_THAT(context.HashKey(0, seed), Eq(HashValue(one_64, seed)));
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EXPECT_THAT(context.HashKey(1, seed), Eq(HashValue(two_64, seed)));
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EXPECT_THAT(context.HashKey(2, seed), Eq(HashValue(one_128, seed)));
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EXPECT_THAT(context.HashKey(3, seed), Eq(HashValue(two_128, seed)));
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EXPECT_THAT(context.HashKey(4, seed), Eq(HashValue(one_64, seed)));
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EXPECT_THAT(context.HashKey(5, seed), Eq(HashValue(one_64, seed)));
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EXPECT_TRUE(context.KeyEq(one_64, 0));
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EXPECT_TRUE(context.KeyEq(one_64, 4));
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EXPECT_TRUE(context.KeyEq(one_64, 5));
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EXPECT_TRUE(context.KeyEq(0, one_64));
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EXPECT_TRUE(context.KeyEq(0, 0));
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EXPECT_TRUE(context.KeyEq(0, 4));
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EXPECT_TRUE(context.KeyEq(4, 5));
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EXPECT_FALSE(context.KeyEq(one_64, 1));
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EXPECT_FALSE(context.KeyEq(one_64, 2));
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EXPECT_FALSE(context.KeyEq(one_64, 3));
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EXPECT_FALSE(context.KeyEq(1, one_64));
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EXPECT_FALSE(context.KeyEq(2, one_64));
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EXPECT_FALSE(context.KeyEq(3, one_64));
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EXPECT_FALSE(context.KeyEq(0, 1));
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EXPECT_FALSE(context.KeyEq(0, 2));
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EXPECT_FALSE(context.KeyEq(4, 3));
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}
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} // namespace
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} // namespace Carbon
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