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Change bold code snippets to inline code blocks

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James Gregory 2013-12-31 17:12:29 +11:00
commit 3c76d884ef
185 changed files with 1772 additions and 1772 deletions
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16
16-04.md
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@ -47,18 +47,18 @@ CMP DH,[EBX+EAX]
Harmless enough, save for two things. First, EBX happened to be zero at
this point (a leftover from an earlier version of the code, as it turned
out), so it was superfluous as a memory-addressing component; this made
it possible to use base-only addressing (**[EAX]**) rather than
base+index addressing (**[EBX+EAX]**), which saves a cycle on the 386.
Second: Changing the instruction to **CMP [EAX],DH** saved 2 cycles—just
it possible to use base-only addressing (`[EAX]`) rather than
base+index addressing (`[EBX+EAX]`), which saves a cycle on the 386.
Second: Changing the instruction to `CMP [EAX],DH` saved 2 cycles—just
enough, by good fortune, to speed up the whole program by 5 percent.
> ![](images/i.jpg)
> **CMP reg,[mem]** takes 6 cycles on the 386, but **CMP [ mem ],reg**
> takes only 5 cycles; you should always perform**CMP** with the memory
> `CMP reg,[mem]` takes 6 cycles on the 386, but `CMP [ mem ],reg`
> takes only 5 cycles; you should always perform`CMP` with the memory
> operand on the left on the 386.
(Granted, **CMP [*mem*],*reg*** is 1 cycle slower than **CMP
*reg*,[*mem*]** on the 286, and they're both the same on the 8088; in
(Granted, `CMP [*mem*],*reg*` is 1 cycle slower than `CMP
*reg*,[*mem*]` on the 286, and they're both the same on the 8088; in
this case, though, the code was specific to the 386. In case you're
curious, both forms take 2 cycles on the 486; quite a lot faster, eh?)
@ -69,7 +69,7 @@ no longer be valid from the 8088/286 world into the wonderful new world
of 386 native-mode programming. The second lesson is that after you've
slaved over your code for a while, you're in no shape to see its flaws,
or to be able to get the new perspectives needed to speed it up. I'll
bet Terje looked at that **[EBX+EAX]** addressing a hundred times while
bet Terje looked at that `[EBX+EAX]` addressing a hundred times while
trying to speed up his code, but he didn't really see what it did;
instead, he saw what it was supposed to do. Mental shortcuts like this
are what enable us to deal with the complexities of assembly language