[Support] Remove findFirstSet and findLastSet

This patch removes findFirstSet and findLastSet as there are no uses
left in LLVM.

I am not aware of any uses of findFirstSet and findLastSet in the
open-source world outside LLVM, so I am skipping the deprecation step.

Differential Revision: https://reviews.llvm.org/D142603

Author: kazutakahirata

llvm/include/llvm/Support/MathExtras.h

@@ -24,14 +24,6 @@
 
 namespace llvm {
 
-/// The behavior an operation has on an input of 0.
-enum ZeroBehavior {
-  /// The returned value is undefined.
-  ZB_Undefined,
-  /// The returned value is numeric_limits<T>::max()
-  ZB_Max
-};
-
 /// Mathematical constants.
 namespace numbers {
 // TODO: Track C++20 std::numbers.
@@ -92,19 +84,6 @@ template <typename T> unsigned countLeadingZeros(T Val) {
   return llvm::countl_zero(Val);
 }
 
-/// Get the index of the first set bit starting from the least
-///   significant bit.
-///
-/// Only unsigned integral types are allowed.
-///
-/// \param ZB the behavior on an input of 0.
-template <typename T> T findFirstSet(T Val, ZeroBehavior ZB = ZB_Max) {
-  if (ZB == ZB_Max && Val == 0)
-    return std::numeric_limits<T>::max();
-
-  return llvm::countr_zero(Val);
-}
-
 /// Create a bitmask with the N right-most bits set to 1, and all other
 /// bits set to 0.  Only unsigned types are allowed.
 template <typename T> T maskTrailingOnes(unsigned N) {
@@ -132,21 +111,6 @@ template <typename T> T maskLeadingZeros(unsigned N) {
   return maskTrailingOnes<T>(CHAR_BIT * sizeof(T) - N);
 }
 
-/// Get the index of the last set bit starting from the least
-///   significant bit.
-///
-/// Only unsigned integral types are allowed.
-///
-/// \param ZB the behavior on an input of 0.
-template <typename T> T findLastSet(T Val, ZeroBehavior ZB = ZB_Max) {
-  if (ZB == ZB_Max && Val == 0)
-    return std::numeric_limits<T>::max();
-
-  // Use ^ instead of - because both gcc and llvm can remove the associated ^
-  // in the __builtin_clz intrinsic on x86.
-  return llvm::countl_zero(Val) ^ (std::numeric_limits<T>::digits - 1);
-}
-
 /// Macro compressed bit reversal table for 256 bits.
 ///
 /// http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable

llvm/unittests/Support/MathExtrasTest.cpp

@@ -90,46 +90,6 @@ TEST(MathExtras, onesMask) {
   EXPECT_EQ(0xFFFFFFFFFFFF0000ULL, maskLeadingOnes<uint64_t>(48U));
 }
 
-TEST(MathExtras, findFirstSet) {
-  uint8_t Z8 = 0;
-  uint16_t Z16 = 0;
-  uint32_t Z32 = 0;
-  uint64_t Z64 = 0;
-  EXPECT_EQ(0xFFULL, findFirstSet(Z8));
-  EXPECT_EQ(0xFFFFULL, findFirstSet(Z16));
-  EXPECT_EQ(0xFFFFFFFFULL, findFirstSet(Z32));
-  EXPECT_EQ(0xFFFFFFFFFFFFFFFFULL, findFirstSet(Z64));
-
-  uint8_t NZ8 = 42;
-  uint16_t NZ16 = 42;
-  uint32_t NZ32 = 42;
-  uint64_t NZ64 = 42;
-  EXPECT_EQ(1u, findFirstSet(NZ8));
-  EXPECT_EQ(1u, findFirstSet(NZ16));
-  EXPECT_EQ(1u, findFirstSet(NZ32));
-  EXPECT_EQ(1u, findFirstSet(NZ64));
-}
-
-TEST(MathExtras, findLastSet) {
-  uint8_t Z8 = 0;
-  uint16_t Z16 = 0;
-  uint32_t Z32 = 0;
-  uint64_t Z64 = 0;
-  EXPECT_EQ(0xFFULL, findLastSet(Z8));
-  EXPECT_EQ(0xFFFFULL, findLastSet(Z16));
-  EXPECT_EQ(0xFFFFFFFFULL, findLastSet(Z32));
-  EXPECT_EQ(0xFFFFFFFFFFFFFFFFULL, findLastSet(Z64));
-
-  uint8_t NZ8 = 42;
-  uint16_t NZ16 = 42;
-  uint32_t NZ32 = 42;
-  uint64_t NZ64 = 42;
-  EXPECT_EQ(5u, findLastSet(NZ8));
-  EXPECT_EQ(5u, findLastSet(NZ16));
-  EXPECT_EQ(5u, findLastSet(NZ32));
-  EXPECT_EQ(5u, findLastSet(NZ64));
-}
-
 TEST(MathExtras, isIntN) {
   EXPECT_TRUE(isIntN(16, 32767));
   EXPECT_FALSE(isIntN(16, 32768));