[libc] Fix forward missing `BigInt` specialization of `mask_leading_ones` / `mask_trailing_ones` (#84325)

#84299 broke the arm32 build, this patch fixes it forward.

7 files changed, 118 insertions, 33 deletions

diff --git a/libc/src/__support/UInt.h b/libc/src/__support/UInt.h
index b3d8f00..925de87 100644
--- a/libc/src/__support/UInt.h
+++ b/libc/src/__support/UInt.h
@@ -1056,4 +1056,60 @@ rotr(T value, int rotate) {
 
 } // namespace LIBC_NAMESPACE::cpp
 
+namespace LIBC_NAMESPACE {
+
+// Specialization of mask_trailing_ones ('math_extras.h') for BigInt.
+template <typename T, size_t count>
+LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_big_int_v<T>, T>
+mask_trailing_ones() {
+  static_assert(!T::SIGNED);
+  if (count == 0)
+    return T();
+  constexpr unsigned T_BITS = CHAR_BIT * sizeof(T);
+  static_assert(count <= T_BITS && "Invalid bit index");
+  using word_type = typename T::word_type;
+  T out;
+  constexpr int CHUNK_INDEX_CONTAINING_BIT =
+      static_cast<int>(count / T::WORD_SIZE);
+  int index = 0;
+  for (auto &word : out.val) {
+    if (index < CHUNK_INDEX_CONTAINING_BIT)
+      word = -1;
+    else if (index > CHUNK_INDEX_CONTAINING_BIT)
+      word = 0;
+    else
+      word = mask_trailing_ones<word_type, count % T::WORD_SIZE>();
+    ++index;
+  }
+  return out;
+}
+
+// Specialization of mask_leading_ones ('math_extras.h') for BigInt.
+template <typename T, size_t count>
+LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_big_int_v<T>, T>
+mask_leading_ones() {
+  static_assert(!T::SIGNED);
+  if (count == 0)
+    return T();
+  constexpr unsigned T_BITS = CHAR_BIT * sizeof(T);
+  static_assert(count <= T_BITS && "Invalid bit index");
+  using word_type = typename T::word_type;
+  T out;
+  constexpr int CHUNK_INDEX_CONTAINING_BIT =
+      static_cast<int>((T::BITS - count - 1ULL) / T::WORD_SIZE);
+  int index = 0;
+  for (auto &word : out.val) {
+    if (index < CHUNK_INDEX_CONTAINING_BIT)
+      word = 0;
+    else if (index > CHUNK_INDEX_CONTAINING_BIT)
+      word = -1;
+    else
+      word = mask_leading_ones<word_type, count % T::WORD_SIZE>();
+    ++index;
+  }
+  return out;
+}
+
+} // namespace LIBC_NAMESPACE
+
 #endif // LLVM_LIBC_SRC___SUPPORT_UINT_H
diff --git a/libc/src/__support/math_extras.h b/libc/src/__support/math_extras.h
index 7a89fbb..c6b458d 100644
--- a/libc/src/__support/math_extras.h
+++ b/libc/src/__support/math_extras.h
@@ -20,21 +20,18 @@ namespace LIBC_NAMESPACE {
 // Create a bitmask with the count right-most bits set to 1, and all other bits
 // set to 0.  Only unsigned types are allowed.
 template <typename T, size_t count>
-LIBC_INLINE constexpr T mask_trailing_ones() {
-  static_assert(cpp::is_unsigned_v<T>);
+LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
+mask_trailing_ones() {
   constexpr unsigned T_BITS = CHAR_BIT * sizeof(T);
   static_assert(count <= T_BITS && "Invalid bit index");
-  // It's important not to initialize T with -1, since T may be BigInt which
-  // will take -1 as a uint64_t and only initialize the low 64 bits.
-  constexpr T ALL_ZEROES(0);
-  constexpr T ALL_ONES(~ALL_ZEROES); // bitwise NOT performs integer promotion.
-  return count == 0 ? 0 : (ALL_ONES >> (T_BITS - count));
+  return count == 0 ? 0 : (T(-1) >> (T_BITS - count));
 }
 
 // Create a bitmask with the count left-most bits set to 1, and all other bits
 // set to 0.  Only unsigned types are allowed.
 template <typename T, size_t count>
-LIBC_INLINE constexpr T mask_leading_ones() {
+LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
+mask_leading_ones() {
   constexpr T MASK(mask_trailing_ones<T, CHAR_BIT * sizeof(T) - count>());
   return T(~MASK); // bitwise NOT performs integer promotion.
 }
diff --git a/libc/src/stdio/printf_core/float_dec_converter.h b/libc/src/stdio/printf_core/float_dec_converter.h
index a6c6832..27d229a 100644
--- a/libc/src/stdio/printf_core/float_dec_converter.h
+++ b/libc/src/stdio/printf_core/float_dec_converter.h
@@ -12,6 +12,7 @@
 #include "src/__support/CPP/string_view.h"
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/rounding_mode.h"
+#include "src/__support/UInt.h" // cpp::is_big_int_v
 #include "src/__support/float_to_string.h"
 #include "src/__support/integer_to_string.h"
 #include "src/__support/libc_assert.h"
@@ -33,7 +34,8 @@ using ExponentString =
 
 // Returns true if value is divisible by 2^p.
 template <typename T>
-LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_integral_v<T>, bool>
+LIBC_INLINE constexpr cpp::enable_if_t<
+    cpp::is_integral_v<T> || cpp::is_big_int_v<T>, bool>
 multiple_of_power_of_2(T value, uint32_t p) {
   return (value & ((T(1) << p) - 1)) == 0;
 }
@@ -76,7 +78,8 @@ LIBC_INLINE RoundDirection get_round_direction(int last_digit, bool truncated,
 }
 
 template <typename T>
-LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_integral_v<T>, bool>
+LIBC_INLINE constexpr cpp::enable_if_t<
+    cpp::is_integral_v<T> || cpp::is_big_int_v<T>, bool>
 zero_after_digits(int32_t base_2_exp, int32_t digits_after_point, T mantissa,
                   const int32_t mant_width) {
   const int32_t required_twos = -base_2_exp - digits_after_point - 1;
diff --git a/libc/test/UnitTest/CMakeLists.txt b/libc/test/UnitTest/CMakeLists.txt
index 36837c5..8a35f12 100644
--- a/libc/test/UnitTest/CMakeLists.txt
+++ b/libc/test/UnitTest/CMakeLists.txt
@@ -104,6 +104,7 @@ add_header_library(
   DEPENDS
     libc.src.__support.CPP.string
     libc.src.__support.CPP.type_traits
+    libc.src.__support.uint
 )
 
 add_unittest_framework_library(
diff --git a/libc/test/UnitTest/StringUtils.h b/libc/test/UnitTest/StringUtils.h
index 54cff97..1e3ba57 100644
--- a/libc/test/UnitTest/StringUtils.h
+++ b/libc/test/UnitTest/StringUtils.h
@@ -11,12 +11,13 @@
 
 #include "src/__support/CPP/string.h"
 #include "src/__support/CPP/type_traits.h"
+#include "src/__support/UInt.h"
 
 namespace LIBC_NAMESPACE {
 
 // Return the first N hex digits of an integer as a string in upper case.
 template <typename T>
-cpp::enable_if_t<cpp::is_integral_v<T>, cpp::string>
+cpp::enable_if_t<cpp::is_integral_v<T> || cpp::is_big_int_v<T>, cpp::string>
 int_to_hex(T value, size_t length = sizeof(T) * 2) {
   cpp::string s(length, '0');
 
diff --git a/libc/test/src/__support/CMakeLists.txt b/libc/test/src/__support/CMakeLists.txt
index 8c861b5..adbacb9 100644
--- a/libc/test/src/__support/CMakeLists.txt
+++ b/libc/test/src/__support/CMakeLists.txt
@@ -27,7 +27,9 @@ add_libc_test(
   SRCS
     math_extras_test.cpp
   DEPENDS
+    libc.src.__support.integer_literals
     libc.src.__support.math_extras
+    libc.src.__support.uint128
 )
 
 add_libc_test(
diff --git a/libc/test/src/__support/math_extras_test.cpp b/libc/test/src/__support/math_extras_test.cpp
index e55d995..ed06436 100644
--- a/libc/test/src/__support/math_extras_test.cpp
+++ b/libc/test/src/__support/math_extras_test.cpp
@@ -6,34 +6,59 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "src/__support/UInt128.h" // UInt128
+#include "src/__support/integer_literals.h"
 #include "src/__support/math_extras.h"
 #include "test/UnitTest/Test.h"
 
 namespace LIBC_NAMESPACE {
 
 TEST(LlvmLibcBlockMathExtrasTest, mask_trailing_ones) {
-  EXPECT_EQ(uint8_t(0), (mask_leading_ones<uint8_t, 0>()));
-  EXPECT_EQ(uint8_t(0), (mask_trailing_ones<uint8_t, 0>()));
-  EXPECT_EQ(uint16_t(0), (mask_leading_ones<uint16_t, 0>()));
-  EXPECT_EQ(uint16_t(0), (mask_trailing_ones<uint16_t, 0>()));
-  EXPECT_EQ(uint32_t(0), (mask_leading_ones<uint32_t, 0>()));
-  EXPECT_EQ(uint32_t(0), (mask_trailing_ones<uint32_t, 0>()));
-  EXPECT_EQ(uint64_t(0), (mask_leading_ones<uint64_t, 0>()));
-  EXPECT_EQ(uint64_t(0), (mask_trailing_ones<uint64_t, 0>()));
-
-  EXPECT_EQ(uint32_t(0x00000003), (mask_trailing_ones<uint32_t, 2>()));
-  EXPECT_EQ(uint32_t(0xC0000000), (mask_leading_ones<uint32_t, 2>()));
-
-  EXPECT_EQ(uint32_t(0x000007FF), (mask_trailing_ones<uint32_t, 11>()));
-  EXPECT_EQ(uint32_t(0xFFE00000), (mask_leading_ones<uint32_t, 11>()));
-
-  EXPECT_EQ(uint32_t(0xFFFFFFFF), (mask_trailing_ones<uint32_t, 32>()));
-  EXPECT_EQ(uint32_t(0xFFFFFFFF), (mask_leading_ones<uint32_t, 32>()));
-  EXPECT_EQ(uint64_t(0xFFFFFFFFFFFFFFFF), (mask_trailing_ones<uint64_t, 64>()));
-  EXPECT_EQ(uint64_t(0xFFFFFFFFFFFFFFFF), (mask_leading_ones<uint64_t, 64>()));
-
-  EXPECT_EQ(uint64_t(0x0000FFFFFFFFFFFF), (mask_trailing_ones<uint64_t, 48>()));
-  EXPECT_EQ(uint64_t(0xFFFFFFFFFFFF0000), (mask_leading_ones<uint64_t, 48>()));
+  EXPECT_EQ(0_u8, (mask_leading_ones<uint8_t, 0>()));
+  EXPECT_EQ(0_u8, (mask_trailing_ones<uint8_t, 0>()));
+  EXPECT_EQ(0_u16, (mask_leading_ones<uint16_t, 0>()));
+  EXPECT_EQ(0_u16, (mask_trailing_ones<uint16_t, 0>()));
+  EXPECT_EQ(0_u32, (mask_leading_ones<uint32_t, 0>()));
+  EXPECT_EQ(0_u32, (mask_trailing_ones<uint32_t, 0>()));
+  EXPECT_EQ(0_u64, (mask_leading_ones<uint64_t, 0>()));
+  EXPECT_EQ(0_u64, (mask_trailing_ones<uint64_t, 0>()));
+
+  EXPECT_EQ(0x00000003_u32, (mask_trailing_ones<uint32_t, 2>()));
+  EXPECT_EQ(0xC0000000_u32, (mask_leading_ones<uint32_t, 2>()));
+
+  EXPECT_EQ(0x000007FF_u32, (mask_trailing_ones<uint32_t, 11>()));
+  EXPECT_EQ(0xFFE00000_u32, (mask_leading_ones<uint32_t, 11>()));
+
+  EXPECT_EQ(0xFFFFFFFF_u32, (mask_trailing_ones<uint32_t, 32>()));
+  EXPECT_EQ(0xFFFFFFFF_u32, (mask_leading_ones<uint32_t, 32>()));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFF_u64, (mask_trailing_ones<uint64_t, 64>()));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFF_u64, (mask_leading_ones<uint64_t, 64>()));
+
+  EXPECT_EQ(0x0000FFFFFFFFFFFF_u64, (mask_trailing_ones<uint64_t, 48>()));
+  EXPECT_EQ(0xFFFFFFFFFFFF0000_u64, (mask_leading_ones<uint64_t, 48>()));
+
+  EXPECT_EQ(0_u128, (mask_trailing_ones<UInt128, 0>()));
+  EXPECT_EQ(0_u128, (mask_leading_ones<UInt128, 0>()));
+
+  EXPECT_EQ(0x00000000000000007FFFFFFFFFFFFFFF_u128,
+            (mask_trailing_ones<UInt128, 63>()));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFE0000000000000000_u128,
+            (mask_leading_ones<UInt128, 63>()));
+
+  EXPECT_EQ(0x0000000000000000FFFFFFFFFFFFFFFF_u128,
+            (mask_trailing_ones<UInt128, 64>()));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFF0000000000000000_u128,
+            (mask_leading_ones<UInt128, 64>()));
+
+  EXPECT_EQ(0x0000000000000001FFFFFFFFFFFFFFFF_u128,
+            (mask_trailing_ones<UInt128, 65>()));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFF8000000000000000_u128,
+            (mask_leading_ones<UInt128, 65>()));
+
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF_u128,
+            (mask_trailing_ones<UInt128, 128>()));
+  EXPECT_EQ(0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF_u128,
+            (mask_leading_ones<UInt128, 128>()));
 }
 
 } // namespace LIBC_NAMESPACE