18 - Introducing to Y86 1 Topics...

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1 Introducing to Y86
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2 Topics Y86 instruction set architecture Suggested Reading: 4.1
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Goal Understanding the instruction encodings Preparing for designing your computer
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Y86 Processor State Program Registers Same 8 as with IA32.  Each 32 bits Condition Codes Single-bit flags set by arithmetic or logical  instructions OF: Overflow ZF: Zero SF: Negative Program Counter Indicates address of instruction Memory Byte-addressable storage array Words stored in little-endian byte order %eax %ecx %edx %ebx %esi %edi %esp %ebp Program registers Condition codes PC Memory OF ZF SF
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Y86 Instructions Format (P259) 1--6 bytes of information read from memory Can determine instruction length from first byte Not as many instruction types, and simpler encoding than with IA32 Each accesses and modifies some part(s) of the program state Errata: JXX and call are 5 bytes long.
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Encoding Registers Each register has 4-bit ID Same encoding as in IA32, but IA32 using only 3-bit ID Register ID 8 indicates “no register” Will use this in our hardware design in multiple places %eax %ecx %edx %ebx %esi %edi %esp %ebp 0 1 2 3 6 7 4 5 1
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Instruction Example Addition Instruction Add value in register rA to that in register rB Store result in register rB Note that Y86 only allows addition to be applied to register data Set condition codes based on result Encoded Representation Generic Form
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This note was uploaded on 10/19/2011 for the course CS 000 taught by Professor Jing during the Fall '10 term at Fudan University.

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18 - Introducing to Y86 1 Topics...

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