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| author | Johannes Stoelp <johannes.stoelp@gmail.com> | 2022-08-24 18:29:49 +0200 |
|---|---|---|
| committer | Johannes Stoelp <johannes.stoelp@gmail.com> | 2022-08-24 18:30:00 +0200 |
| commit | e3e0053fbe27a3c2e537f5ab5866aa620631d66f (patch) | |
| tree | 6555c6c0382c63d530b90a6d57729caa10f2d302 /src/development/gcc.md | |
| parent | 087e4222f1964de9fbef1b11f1344b0f93cefbe2 (diff) | |
| download | notes-e3e0053fbe27a3c2e537f5ab5866aa620631d66f.tar.gz notes-e3e0053fbe27a3c2e537f5ab5866aa620631d66f.zip | |
gcc: Enhance builtin_expect description
Diffstat (limited to 'src/development/gcc.md')
| -rw-r--r-- | src/development/gcc.md | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/src/development/gcc.md b/src/development/gcc.md index 88e44fc..39ae753 100644 --- a/src/development/gcc.md +++ b/src/development/gcc.md @@ -29,6 +29,10 @@ Give the compiler a hint which branch is hot, so it can lay out the code accordingly to reduce number of jump instructions. See on [compiler explorer](https://godbolt.org/z/MbTHAP). +The semantics of this hint are as follows, the compiler prioritises `expr == +cond`. So `__builtin_expect(expr, 0)` means that we expect the `expr` to be `0` +most of the time. + ```bash echo " extern void foo(); |