Array access
Accessing memory in an array includes performing a first instruction, including by determining whether an index used by the first instruction is within a valid range and in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index. Accessing memory in the array further includes, in the event that the index is within a valid range, performing a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction.
1. A method of accessing memory in an array, comprising:
performing a first instruction, including:
determining whether an index used by the first instruction is within a valid range; and
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within a valid range, performing a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein the first instruction does not include an array length field.
2. A method as recited in claim 1 , wherein performing the first instruction further includes, in the event that the index is not within the valid range, indicating that an error has occurred.
3. A method as recited in claim 1 , wherein determining whether the index used by the first instruction is within the valid range includes sign extending the index.
4. A method as recited in claim 1 , wherein determining whether the index used by the first instruction is within the valid range includes comparing the index with the array length field.
5. A method as recited in claim 1 , wherein determining whether the index used by the first instruction is within the valid range includes performing an unsigned comparison of the index and the array length field.
6. A method as recited in claim 1 , wherein determining whether the index used by the first instruction is within the valid range includes comparing the index with a minimum valid index and with a maximum valid index.
7. A method as recited in claim 6 , wherein the minimum valid index has a default value of zero.
8. A method as recited in claim 1 , wherein the first instruction includes an index field, an array address field, and a register field for storing the determined memory address.
9. A method as recited in claim 1 , wherein accessing the array element includes reading a value from the array element.
10. A method as recited in claim 1 , wherein accessing the array element includes storing a value to the array element.
11. A method as recited in claim 1 , wherein the second instruction determines an address of the array element based on an offset field and the memory address determined by the first instruction.
12. A method as recited in claim 11 , wherein the second instruction determines the address of the array element by adding the offset to the memory address determined by the first instruction.
13. A method as recited in claim 11 , wherein the second instruction determines the address of the array element by scaling the offset and adding the scaled offset to the memory address determined by the first instruction.
14. A method as recited in claim 1 , wherein the first and the second instructions each performs exactly one memory access operation.
15. A method as recited in claim 1 , wherein the first instruction and the second instruction are selected from a plurality of instructions, and the selection being dependent at least in part on the size of the array element.
16. A method of accessing memory in an array, comprising:
performing a first instruction, including:
determining whether an index used by the first instruction is within a valid range; and
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within a valid range, performing a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein the first instruction is provided with an array address field indicating the address of an array data structure, and determining whether the index used by the first instruction is within the valid range includes loading a length value stored at a fixed offset from the address of the array data structure.
17. A method of accessing memory in an array, comprising:
performing a first instruction, including:
determining whether an index used by the first instruction is within a valid range; and
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within a valid range, performing a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein the first instruction is provided with an array address field indicating the address of an array data structure, and determining whether the index used by the first instruction is within the valid range includes loading a minimum valid range value stored at a fixed offset from the address of the array data structure.
18. A method of accessing memory in an array, comprising:
performing a first instruction, including:
determining whether an index used by the first instruction is within a valid range; and
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within a valid range, performing a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein the first instruction is provided with an array address field indicating the address of an array data structure, and determining whether the index used by the first instruction is within range includes loading a maximum valid range value stored in memory at a fixed offset from the address of the array data structure.
19. A method of accessing memory in an array, comprising:
performing a first instruction, including:
determining whether an index used by the first instruction is within a valid range; and
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within a valid range, performing a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein determining the memory address related to the array element includes shifting the index to obtain a shifted value that equals the index multiplied by the size of an element in the array, and adding the shifted value to a reference.
20. A processor comprising:
a logical unit configured to access an array, including to:
perform a first instruction, including:
determining whether an index used by the first instruction is within a valid range,
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within the valid range, perform a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein the first instruction does not include an array length field; and
a memory coupled to the logic unit, configured to store the array.
21. The processor of claim 20 , wherein performing the first instruction further includes, in the event that the index is not within the valid range, indicating that an error has occurred.
22. The processor of claim 20 , wherein determining whether the index used by the first instruction is within the valid range includes sign extending the index.
23. The processor of claim 20 , wherein determining whether the index used by the first instruction is within the valid range includes comparing the index with the array length field.
24. The processor of claim 20 , wherein determining whether the index used by the first instruction is within the valid range includes performing an unsigned comparison of the index and the array length field.
25. The processor of claim 20 , wherein the first instruction includes an index field, an array address field, and a register field for storing the determined memory address.
26. The processor of claim 20 , wherein the first and the second instructions each performs exactly one memory access operation.
27. The processor of claim 20 , wherein the first instruction and the second instruction are selected from a plurality of instructions, and the selection being dependent at least in part on the size of the array element.
28. A system for accessing memory in an array, comprising:
a processor configured to:
perform a first instruction, including:
determining whether an index used by the first instruction is within a valid range,
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within the valid range, perform a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein the first instruction does not include an array length field; and
a memory coupled to the processor, configured to the provide the processor with the first and the second instruction.
29. The system of claim 28 , wherein performing the first instruction further includes, in the event that the index is not within the valid range, indicating that an error has occurred.
30. The system of claim 28 , wherein determining whether the index used by the first instruction is within the valid range includes sign extending the index.
31. The system of claim 28 , wherein determining whether the index used by the first instruction is within the valid range includes comparing the index with the array length field.
32. The system of claim 28 , wherein determining whether the index used by the first instruction is within the valid range includes performing an unsigned comparison of the index and the array length field.
33. The system of claim 28 , wherein the first instruction includes an index field, an array address field, and a register field for storing the determined memory address.
34. The system of claim 28 , wherein the first and the second instructions each performs exactly one memory access operation.
35. The system of claim 28 , wherein the first instruction and the second instruction are selected from a plurality of instructions, and the selection being dependent at least in part on the size of the array element.
36. A processor comprising:
a logical unit configured to access an array, including to:
perform a first instruction, including:
determining whether an index used by the first instruction is within a valid range,
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within the valid range, perform a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein the first instruction is provided with an array address field indicating the address of an array data structure, and determining whether the index used by the first instruction is within the valid range includes loading a length value stored at a fixed offset from the address of the array data structure; and
a memory coupled to the logic unit, configured to store the array.
37. A system for accessing memory in an array, comprising:
a processor configured to:
perform a first instruction, including:
determining whether an index used by the first instruction is within a valid range,
in the event that the index is within a valid range, determining a memory address related to an array element that corresponds to the index; and
in the event that the index is within the valid range, perform a second instruction to access the array element, the access being based at least in part on the memory address determined by the first instruction;
wherein the first instruction is provided with an array address field indicating the address of an array data structure, and determining whether the index used by the first instruction is within the valid range includes loading a length value stored at a fixed offset from the address of the array data structure; and
a memory coupled to the processor, configured to the provide the processor with the first and the second instruction.