| 1 |
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| 2 | Some notes on implementing bit-wise operations in CIVL:
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| 3 |
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| 4 | Read C11 6.2.6 on Representation of Types, esp. integer types.
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| 5 |
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| 6 | 6.5.7 Bitwise shift operators
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| 7 |
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| 8 | The integer promotions are performed on each of the operands.
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| 9 | The type of the result is that of the promoted left operand.
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| 10 | If the value of the right operand is negative or is
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| 11 | greater than or equal to the width of the promoted left operand,
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| 12 | the behavior is undefined.
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| 13 |
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| 14 | The result of E1 << E2 is E1 left-shifted E2 bit positions;
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| 15 | vacated bits are filled with zeros. If E1 has an unsigned type,
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| 16 | the value of the result is E1 * 2^E2, reduced modulo one more
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| 17 | than the maximum value representable in the result type.
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| 18 | If E1 has a signed type and nonnegative value, and E1 * 2^E2
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| 19 | is representable in the result type, then that is the resulting
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| 20 | value; otherwise, the behavior is undefined.
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| 21 |
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| 22 | The result of E1 >> E2 is E1 right-shifted E2 bit positions.
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| 23 | If E1 has an unsigned type or if E1 has a signed type and a
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| 24 | nonnegative value, the value of the result is the integral
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| 25 | part of the quotient of E1 / 2E2. If E1 has a signed type
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| 26 | and a negative value, the resulting value is
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| 27 | implementation-defined.
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| 28 |
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| 29 | See 6.5.10--12 for the bit-wise and, inclusive or, exclusive or
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| 30 | operations. But all it says is that these are the bit-wise
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| 31 | operations.
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