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Clarify the meaning of branch hints #36

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yuri91 merged 1 commit into from
May 26, 2025
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Clarify the meaning of branch hints #36

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6 changes: 3 additions & 3 deletions document/metadata/code/binary.rst
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Expand Up @@ -45,7 +45,7 @@ A Branch Hint is a code metadata item with format *branch_hint*.

It can only be attached to |BRIF| and |IF| instructions.

Its payload indicates whether the branch is likely or unlikely to be taken.
Its payload indicates whether the branch's condition is likely or unlikely to be true.

All branch hints for a module are contained in a single code metadata section
with name *'metadata.code.branch_hint'*.
Expand All @@ -64,6 +64,6 @@ with name *'metadata.code.branch_hint'*.
\end{array}
.. index:: ! branch hint section

A value of |Blikely| means that the branch is likely to be taken, while a
A value of |Blikely| means that the branch's condition is likely to be true, while a
value of |Bunlikely| means the opposite. A branch with no hints is considered
equally likely to be taken or not.
equally likely to have its condition be true or not.
10 changes: 5 additions & 5 deletions proposals/branch-hinting/Overview.md
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Expand Up @@ -86,7 +86,7 @@ https://github.com/WebAssembly/meetings/blob/main/main/2021/CG-11-09.md
The *branch hint section* is a **custom section** whose name string is `metadata.code.branch_hint`.
The branch hints section should appear only once in a module, and only before the code section.

The purpose of this section is to aid the compilation of conditional branch instructions, by providing a hint that a branch is very likely (or unlikely) to be taken.
The purpose of this section is to aid the compilation of conditional branch instructions, by providing a hint that a branch's condition is very likely (or unlikely) to be true.

The section contains a vector of *function branch hints* each representing the branch hints for a single function.

Expand All @@ -104,10 +104,10 @@ Each *branch hint* structure consists of
* A |U32| with value `1`,
* a |U32| indicating the meaning of the hint:

| value | meaning |
|-------|-------------------|
| 0 | likely not taken |
| 1 | likely taken |
| value | meaning |
|-------|---------------------------|
| 0 | condition is likely false |
| 1 | condition is likely true |

Elements of the vector of *branch hint* must appear in increasing byte offset order,
and a byte offset can appear at most once. A |BRIF| or |IF| instruction must be present
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