[clang] [clang] Introduce elementwise ctlz/cttz builtins (PR #131995)

[Fraser Cormack via cfe-commits]

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@@ -860,3 +860,41 @@ static_assert(__builtin_elementwise_sub_sat(0U, 1U) == 0U);
 static_assert(__builtin_bit_cast(unsigned, __builtin_elementwise_sub_sat((vector4char){5, 4, 3, 2}, (vector4char){1, 1, 1, 1})) == (LITTLE_END ? 0x01020304 : 0x04030201));
 static_assert(__builtin_bit_cast(unsigned, __builtin_elementwise_sub_sat((vector4uchar){5, 4, 3, 2}, (vector4uchar){1, 1, 1, 1})) == (LITTLE_END ? 0x01020304U : 0x04030201U));
 static_assert(__builtin_bit_cast(unsigned long long, __builtin_elementwise_sub_sat((vector4short){(short)0x8000, (short)0x8001, (short)0x8002, (short)0x8003}, (vector4short){7, 8, 9, 10}) == (LITTLE_END ? 0x8000800080008000 : 0x8000800080008000)));
+
+static_assert(__builtin_elementwise_ctlz(2) == 30);
+static_assert(__builtin_elementwise_ctlz(2, 8) == 30);
+static_assert(__builtin_elementwise_ctlz(0, 8) == 8);
+static_assert(__builtin_elementwise_ctlz((char)2) == 6);
+static_assert(__builtin_elementwise_ctlz((short)2) == 14);
+static_assert(__builtin_elementwise_ctlz((char)1) == 0x7);
+static_assert(__builtin_elementwise_ctlz((char)4) == 0x5);
+static_assert(__builtin_elementwise_ctlz((char)127) == 0x1);
+static_assert(__builtin_elementwise_ctlz((char)128) == 0x0);
+static_assert(__builtin_bit_cast(unsigned, __builtin_elementwise_ctlz((vector4char){1, 4, 127, (char)128})) == (LITTLE_END ? 0x00010507 : 0x07050100));
+
+constexpr int clz0 = __builtin_elementwise_ctlz(0);
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frasercrmck wrote:

Good idea, I've added those tests now.

https://github.com/llvm/llvm-project/pull/131995