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Add some comments to assembler.c #1

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@pablogsal
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@pablogsal pablogsal commented Dec 18, 2019

Meanwhile I familiarise myself with the design, here is a first batch of comments that will help reading the source in the future.

@pablogsal pablogsal force-pushed the pablogsal:better-code-generation branch from 7f967e6 to 06a7f4a Dec 18, 2019
@markshannon markshannon force-pushed the markshannon:better-code-generation branch from b97c765 to 925ac6c Dec 22, 2019
@pablogsal pablogsal force-pushed the pablogsal:better-code-generation branch from 06a7f4a to 6144691 Dec 26, 2019
@markshannon markshannon force-pushed the markshannon:better-code-generation branch 3 times, most recently from bcf616d to f09a15f Jan 7, 2020
markshannon pushed a commit that referenced this pull request Jun 22, 2020
```
Direct leak of 8 byte(s) in 1 object(s) allocated from:
    #0 0x7f008bf19667 in __interceptor_malloc (/lib64/libasan.so.6+0xb0667)
    #1 0x7f007a0bee4a in subprocess_fork_exec /home/heimes/dev/python/cpython/Modules/_posixsubprocess.c:774
    python#2 0xe0305b in cfunction_call Objects/methodobject.c:546
```

Signed-off-by: Christian Heimes <christian@python.org>
@pablogsal pablogsal closed this Nov 16, 2020
@pablogsal pablogsal deleted the pablogsal:better-code-generation branch Nov 16, 2020
markshannon pushed a commit that referenced this pull request Nov 23, 2020
* bpo-40791: Make compare_digest more constant-time.

The existing volatile `left`/`right` pointers guarantee that the reads will all occur, but does not guarantee that they will be _used_. So a compiler can still short-circuit the loop, saving e.g. the overhead of doing the xors and especially the overhead of the data dependency between `result` and the reads. That would change performance depending on where the first unequal byte occurs. This change removes that optimization.

(This is change #1 from https://bugs.python.org/issue40791 .)
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