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bug#65491: [PATCH] Improve performance allocating vectors
From: |
Stefan Monnier |
Subject: |
bug#65491: [PATCH] Improve performance allocating vectors |
Date: |
Sun, 17 Sep 2023 22:27:43 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) |
>> Even converting them back to their original pointer (which is what we do
>> with tag/untag pairs) is documented to be well-defined if you compile
>> using GCC.
> Only if the consequent pointer designates the same object as the initial
> pointer (of which I see no scrutable definition within GCC's
> documentation.)
IIUC the "if" here is talking about the fact that if the object is
deallocated between the two casts, then you're on your own, of course.
>> In contrast the pointer arithmetic on NULL pointers appears to be
>> something which compilers have started to (ab)use as an assumption for
>> their optimizations. Hence the need to update our code.
> Hmm? Where in this thread was that fact established?
IIUC Mattias bumped into this after he made a few "innocent looking"
changes to the vector allocation code.
Stefan
- bug#65491: [PATCH] Improve performance allocating vectors, Mattias Engdegård, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Eli Zaretskii, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Eli Zaretskii, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Mattias Engdegård, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Eli Zaretskii, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Mattias Engdegård, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Eli Zaretskii, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Po Lu, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Stefan Monnier, 2023/09/17
- bug#65491: [PATCH] Improve performance allocating vectors, Po Lu, 2023/09/17
- bug#65491: [PATCH] Improve performance allocating vectors,
Stefan Monnier <=
- bug#65491: [PATCH] Improve performance allocating vectors, Po Lu, 2023/09/17
- bug#65491: [PATCH] Improve performance allocating vectors, Stefan Monnier, 2023/09/18
- bug#65491: [PATCH] Improve performance allocating vectors, Mattias Engdegård, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Eli Zaretskii, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Mattias Engdegård, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Eli Zaretskii, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Mattias Engdegård, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Paul Eggert, 2023/09/16
- bug#65491: [PATCH] Improve performance allocating vectors, Eli Zaretskii, 2023/09/17
- bug#65491: [PATCH] Improve performance allocating vectors, Paul Eggert, 2023/09/17