[llvm] r374758 - [Alignment][NFC] Support compile time constants
Guillaume Chatelet via llvm-commits
llvm-commits at lists.llvm.org
Mon Oct 14 02:04:16 PDT 2019
Author: gchatelet
Date: Mon Oct 14 02:04:15 2019
New Revision: 374758
URL: http://llvm.org/viewvc/llvm-project?rev=374758&view=rev
Log:
[Alignment][NFC] Support compile time constants
Summary:
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790
Reviewers: courbet
Subscribers: llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D68936
Modified:
llvm/trunk/include/llvm/Support/Alignment.h
llvm/trunk/include/llvm/Support/MathExtras.h
llvm/trunk/unittests/Support/AlignmentTest.cpp
llvm/trunk/unittests/Support/MathExtrasTest.cpp
Modified: llvm/trunk/include/llvm/Support/Alignment.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Alignment.h?rev=374758&r1=374757&r2=374758&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/Alignment.h (original)
+++ llvm/trunk/include/llvm/Support/Alignment.h Mon Oct 14 02:04:15 2019
@@ -53,14 +53,25 @@ private:
friend unsigned encode(struct MaybeAlign A);
friend struct MaybeAlign decodeMaybeAlign(unsigned Value);
+ /// A trivial type to allow construction of constexpr Align.
+ /// This is currently needed to workaround a bug in GCC 5.3 which prevents
+ /// definition of constexpr assign operators.
+ /// https://stackoverflow.com/questions/46756288/explicitly-defaulted-function-cannot-be-declared-as-constexpr-because-the-implic
+ /// FIXME: Remove this, make all assign operators constexpr and introduce user
+ /// defined literals when we don't have to support GCC 5.3 anymore.
+ /// https://llvm.org/docs/GettingStarted.html#getting-a-modern-host-c-toolchain
+ struct LogValue {
+ uint8_t Log;
+ };
+
public:
/// Default is byte-aligned.
constexpr Align() = default;
/// Do not perform checks in case of copy/move construct/assign, because the
/// checks have been performed when building `Other`.
- Align(const Align &Other) = default;
+ constexpr Align(const Align &Other) = default;
+ constexpr Align(Align &&Other) = default;
Align &operator=(const Align &Other) = default;
- Align(Align &&Other) = default;
Align &operator=(Align &&Other) = default;
explicit Align(uint64_t Value) {
@@ -80,6 +91,20 @@ public:
/// would be better than
/// `if (A > Align(1))`
constexpr static const Align None() { return Align(); }
+
+ /// Allow constructions of constexpr Align.
+ template <size_t kValue> constexpr static LogValue Constant() {
+ return LogValue{CTLog2<kValue>()};
+ }
+
+ /// Allow constructions of constexpr Align from types.
+ /// Compile time equivalent to Align(alignof(T)).
+ template <typename T> constexpr static LogValue Of() {
+ return Constant<std::alignment_of<T>::value>();
+ }
+
+ /// Constexpr constructor from LogValue type.
+ constexpr Align(LogValue CA) : ShiftValue(CA.Log) {}
};
/// Treats the value 0 as a 1, so Align is always at least 1.
Modified: llvm/trunk/include/llvm/Support/MathExtras.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/MathExtras.h?rev=374758&r1=374757&r2=374758&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/MathExtras.h (original)
+++ llvm/trunk/include/llvm/Support/MathExtras.h Mon Oct 14 02:04:15 2019
@@ -560,6 +560,16 @@ inline unsigned countPopulation(T Value)
return detail::PopulationCounter<T, sizeof(T)>::count(Value);
}
+/// Compile time Log2.
+/// Valid only for positive powers of two.
+template <size_t kValue> constexpr inline size_t CTLog2() {
+ static_assert(kValue > 0 && llvm::isPowerOf2_64(kValue),
+ "Value is not a valid power of 2");
+ return 1 + CTLog2<kValue / 2>();
+}
+
+template <> constexpr inline size_t CTLog2<1>() { return 0; }
+
/// Return the log base 2 of the specified value.
inline double Log2(double Value) {
#if defined(__ANDROID_API__) && __ANDROID_API__ < 18
Modified: llvm/trunk/unittests/Support/AlignmentTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/AlignmentTest.cpp?rev=374758&r1=374757&r2=374758&view=diff
==============================================================================
--- llvm/trunk/unittests/Support/AlignmentTest.cpp (original)
+++ llvm/trunk/unittests/Support/AlignmentTest.cpp Mon Oct 14 02:04:15 2019
@@ -21,6 +21,28 @@ using namespace llvm;
namespace {
+TEST(AlignmentTest, AlignOfConstant) {
+ EXPECT_EQ(Align::Of<uint8_t>(), Align(alignof(uint8_t)));
+ EXPECT_EQ(Align::Of<uint16_t>(), Align(alignof(uint16_t)));
+ EXPECT_EQ(Align::Of<uint32_t>(), Align(alignof(uint32_t)));
+ EXPECT_EQ(Align::Of<uint64_t>(), Align(alignof(uint64_t)));
+}
+
+TEST(AlignmentTest, AlignConstant) {
+ EXPECT_EQ(Align::Constant<1>(), Align(1));
+ EXPECT_EQ(Align::Constant<2>(), Align(2));
+ EXPECT_EQ(Align::Constant<4>(), Align(4));
+ EXPECT_EQ(Align::Constant<8>(), Align(8));
+ EXPECT_EQ(Align::Constant<16>(), Align(16));
+ EXPECT_EQ(Align::Constant<32>(), Align(32));
+ EXPECT_EQ(Align::Constant<64>(), Align(64));
+}
+
+TEST(AlignmentTest, AlignConstexprConstant) {
+ constexpr Align kConstantAlign = Align::Of<uint64_t>();
+ EXPECT_EQ(Align(8), kConstantAlign);
+}
+
std::vector<uint64_t> getValidAlignments() {
std::vector<uint64_t> Out;
for (size_t Shift = 0; Shift < 64; ++Shift)
Modified: llvm/trunk/unittests/Support/MathExtrasTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/MathExtrasTest.cpp?rev=374758&r1=374757&r2=374758&view=diff
==============================================================================
--- llvm/trunk/unittests/Support/MathExtrasTest.cpp (original)
+++ llvm/trunk/unittests/Support/MathExtrasTest.cpp Mon Oct 14 02:04:15 2019
@@ -203,6 +203,25 @@ TEST(MathExtras, PowerOf2Floor) {
EXPECT_EQ(4U, PowerOf2Floor(7U));
}
+TEST(MathExtras, CTLog2) {
+ EXPECT_EQ(CTLog2<1ULL << 0>(), 0U);
+ EXPECT_EQ(CTLog2<1ULL << 1>(), 1U);
+ EXPECT_EQ(CTLog2<1ULL << 2>(), 2U);
+ EXPECT_EQ(CTLog2<1ULL << 3>(), 3U);
+ EXPECT_EQ(CTLog2<1ULL << 4>(), 4U);
+ EXPECT_EQ(CTLog2<1ULL << 5>(), 5U);
+ EXPECT_EQ(CTLog2<1ULL << 6>(), 6U);
+ EXPECT_EQ(CTLog2<1ULL << 7>(), 7U);
+ EXPECT_EQ(CTLog2<1ULL << 8>(), 8U);
+ EXPECT_EQ(CTLog2<1ULL << 9>(), 9U);
+ EXPECT_EQ(CTLog2<1ULL << 10>(), 10U);
+ EXPECT_EQ(CTLog2<1ULL << 11>(), 11U);
+ EXPECT_EQ(CTLog2<1ULL << 12>(), 12U);
+ EXPECT_EQ(CTLog2<1ULL << 13>(), 13U);
+ EXPECT_EQ(CTLog2<1ULL << 14>(), 14U);
+ EXPECT_EQ(CTLog2<1ULL << 15>(), 15U);
+}
+
TEST(MathExtras, ByteSwap_32) {
EXPECT_EQ(0x44332211u, ByteSwap_32(0x11223344));
EXPECT_EQ(0xDDCCBBAAu, ByteSwap_32(0xAABBCCDD));
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