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Note:
Alpha implementations will impose a significant performance penalty when accessing longwords that are not naturally aligned. (A naturally aligned longword datum has zero as the
2.2.8 Quadword Integer Format in Floating-Point Unit
A quadword integer operand occupies 64 bits in memory, arranged as shown in Figure
Figure 2–21: Quadword Integer Datum
31 30 | 0 |
S
Integer Lo | :A |
Integer Hi | :A+4 |
A quadword integer operand occupies 64 bits in a floating register, arranged as shown in Fig- ure
Figure 2–22: Quadword Integer Floating-Register Format
63 62 | 32 31 | 0 |
S
Integer Hi
Integer Lo
:Fx
There is no explicit quadword load or store instruction; the T_floating load/store instructions are used to move quadword data between memory and the floating registers. (The ITOFT and FTOIT are used to move quadword data between integer and floating registers.)
The T_floating load instruction performs no bit reordering on input. The T_floating store instruction performs no bit reordering on output. This instruction does no checking of the data; when used to store quadwords, the preceding operation should have specified a quadword result.
Note:
Alpha implementations will impose a significant performance penalty when accessing quadwords that are not naturally aligned. (A naturally aligned quadword datum has zero as the
2.2.9Data Types with No Hardware Support
•The following VAX data types are not directly supported in Alpha hardware. Octaword
•H_floating
•D_floating (except load/store and convert to/from G_floating)
•
•Character String