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| -rw-r--r-- | content/posts/pointer-tagging/index.md | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/content/posts/pointer-tagging/index.md b/content/posts/pointer-tagging/index.md index 3794ade..7835e3d 100644 --- a/content/posts/pointer-tagging/index.md +++ b/content/posts/pointer-tagging/index.md @@ -14,10 +14,10 @@ that can reduce memory footprint and boost performance. Despite having a widespread usage and long history[^tagarch], pointer tagging remains a relatively obscure topic. That's because most of its applications are very low level, -such as operating systems and programming language interpreters. +in operating systems and programming language interpreters. -We will look behind the scenes, analyzing and implementing them, -with a focus on applications in language development. +We will look behind the scenes, analyzing and implementing this technique, +with a focus on its uses in language development. ## Preliminary theory @@ -239,11 +239,17 @@ This is particularly used in languages where double is the dominant number type[ The V8 JavaScript engine uses **pointer compression**[^v8]. Instead of using real addresses, all the allocations are represented by 32-bit offsets in a 4 GiB heap. -By *compressing* the pointer size, the memory footprint is reduced by up to 40%. +By *compressing* the pointer size, the memory footprint can be reduced by up to 40%. ## Tagged union implementation +After all this theory and considerations, we can finally move on to the implementation. +But before delving into the pointer tagging techniques we just described, +let's start from the tagged union representation. +The implementation will be fairly trivial, but it will introduce the value types and +coding style that we will use from now on. + ```c typedef enum { |