Topic: DMD0528
Math Unsigned Shift Right Operator
The Math Shift Right operator ( >>> ) causes the bits in left operand to be shifted to the right by the number of positions specified by the right operand. An Unsigned Right Shift is a logical shift which means that the bits that are shifted off the end are discarded. The bit positions that have been vacated by the Unsigned Right Shift operation are zero-filled.
The number of bit positions to shift should be between 1 and the maximum number of bit positions in the left operand. Executing an Unsigned Right Shift with a bit count higher than the number of bit positions in the left operand is not an error but will yield a result of 0. Executing an Unsigned Right Shift by 0 bits has no effect. Executing a Right Shift with a negative value for the bit count is undefined; the result will be 0.
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Unsigned Integers: assume V0 = 0x1234
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V1 = V0 >>> 5
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V1 = 0x1234 >>> 5
0000_0000_0000_0000_0001_0010_0011_0100 - initial bit pattern 0000_0000_0000_0000_0000_0000_1001_0001 - after 5th right shift
V1 = 0x91
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One operand is an unsigned integer memory locations, the other is an integer constant.
The 16-bit integer is sign-extended to 32-bits when it is loaded into the math stack.
The lower 5 bits are shifted out. The remaining 11 bits are shifted into the lowest 11 bit positions. The upper 5 positions are filled with 0's.
The result is placed in an unsigned integer memory location.
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Signed Integers: assume D0 = -12345678
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D1 = D0 >>> 5
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D1 = -12345678 >>> 5
1111_1111_0100_0011_1001_1110_1011_0010 - initial bit pattern 0000_0111_1111_1010_0001_1100_1111_0101 - after 5th right shift
D1 = 133831925
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One operand is an unsigned integer memory locations, the other is an integer constant.
The lower 5 bits are shifted out. The remaining 11 bits are shifted into the lowest 11 bit positions. The upper 5 positions are filled with 0's.
The result is placed in a signed integer memory location.
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N1 = N0 >>> 5
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N1 = -12345 >>> 5
1111_1111_1111_1111_1100_1111_1100_0111 - initial bit pattern 0000_0111_1111_1111_1111_1110_0111_1110 - after 5th right shift
N1 = -386
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One operand is an unsigned integer memory locations, the other is an integer constant.
The 16-bit integer is sign-extended to 32-bits when it is loaded into the math stack.
The lower 5 bits are shifted out. The remaining 11 bits are shifted into the lowest 11 bit positions. The upper 5 positions are filled with 0's.
The result is placed in a signed integer memory location.
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See Also:
Unsigned Shift Right
Related Topics: