New answers tagged design-choices
2
votes
Why does the x86 not have an instruction to obtain its instruction pointer?
OP specifically clarifies interest in a historical reason. Intel would have to give their exact reasoning but the following points are worth noting.
Intel's 8086 and 8088 were outgrowths of their ...
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3
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Why does the x86 not have an instruction to obtain its instruction pointer?
There's a highly-upvoted comment, also requoted in this question's highest-voted answer, saying What would you need it for?
So let me tell you about the coolest piece of code I ever wrote, because ...
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11
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Why does the x86 not have an instruction to obtain its instruction pointer?
So long as a stack exists, the IP address may easily be obtained via the byte sequence "E8 00 00 5B" [CALL $+3 : POP BX] because near calls use PC-relative addressing. On the other hand, ...
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10
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Why does the x86 not have an instruction to obtain its instruction pointer?
On 8086 the instruction pointer is not a general purpose register you can freely access for reading. On earlier 808x models this was also the case, even though program counter was directly used to ...
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15
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Accepted
Why does the x86 not have an instruction to obtain its instruction pointer?
As Thorbjørn Ravn Andersen already put it nicely:
What would you need it for?
There is almost no practical (*1) need to obtain the PC address at runtime (*2) - it's a value to be obtained during ...
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