vasilito
cb424d7448
verify-patch-sanity.py validates every active recipe .patch has internally- consistent hunk line counts — catching the 'malformed patch at line N' failure at commit/CI/preflight time instead of hours into a cook. This cycle hit that class three times (qtwaylandscanner, sddm, xwayland), each only discovered when cookbook tried to apply the patch. Running it across the repo found 29 latent malformed patches (validated against GNU patch: e.g. relibc/P3-sysv-ipc reproduces 'malformed patch at line 22'). They were harmless only because they sit in vendored recipes (baked, not re- applied) — but would fail on any version-bump re-derivation. --fix recounts the hunk headers (body untouched) and repaired all 29. Wired into build-preflight.sh (Phase 1.0D) and redbear-ci.yml, with a unit test (test-patch-sanity.sh). Skips archived/legacy trees and unvalidatable formats (empty placeholders, bare-@@ git hunks).
129 lines
4.7 KiB
ReStructuredText
129 lines
4.7 KiB
ReStructuredText
=========================
|
|
LLVM PC Sections Metadata
|
|
=========================
|
|
|
|
.. contents::
|
|
:local:
|
|
|
|
Introduction
|
|
============
|
|
|
|
PC Sections Metadata can be attached to instructions and functions, for which
|
|
addresses, viz. program counters (PCs), are to be emitted in specially encoded
|
|
binary sections. Metadata is assigned as an ``MDNode`` of the ``MD_pcsections``
|
|
(``!pcsections``) kind; the following section describes the metadata format.
|
|
|
|
Metadata Format
|
|
===============
|
|
|
|
An arbitrary number of interleaved ``MDString`` and constant operators can be
|
|
added, where a new ``MDString`` always denotes a section name, followed by an
|
|
arbitrary number of auxiliary constant data encoded along the PC of the
|
|
instruction or function. The first operator must be a ``MDString`` denoting the
|
|
first section.
|
|
|
|
.. code-block:: none
|
|
|
|
!0 = !{
|
|
!"<section#1>"
|
|
[ , !1 ... ]
|
|
[ !"<section#2">
|
|
[ , !2 ... ]
|
|
... ]
|
|
}
|
|
!1 = !{ iXX <aux-consts#1>, ... }
|
|
!2 = !{ iXX <aux-consts#2>, ... }
|
|
...
|
|
|
|
The occurrence of ``section#1``, ``section#2``, ..., ``section#N`` in the
|
|
metadata causes the backend to emit the PC for the associated instruction or
|
|
function to all named sections. For each emitted PC in a section #N, the
|
|
constants ``aux-consts#N`` in the tuple ``!N`` will be emitted after the PC.
|
|
Multiple tuples with constant data may be provided after a section name string
|
|
(e.g. ``!0 = !{"s1", !1, !2}``), and a single constant tuple may be reused for
|
|
different sections (e.g. ``!0 = !{"s1", !1, "s2", !1}``).
|
|
|
|
Binary Encoding
|
|
===============
|
|
|
|
*Instructions* result in emitting a single PC, and *functions* result in
|
|
emission of the start of the function and a 32-bit size. This is followed by
|
|
the auxiliary constants that followed the respective section name in the
|
|
``MD_pcsections`` metadata.
|
|
|
|
To avoid relocations in the final binary, each PC address stored at ``entry``
|
|
is a relative relocation, computed as ``pc - entry``. To decode, a user has to
|
|
compute ``entry + *entry``.
|
|
|
|
The size of each entry depends on the code model. With large and medium sized
|
|
code models, the entry size matches pointer size. For any smaller code model
|
|
the entry size is just 32 bits.
|
|
|
|
Encoding Options
|
|
----------------
|
|
|
|
Optional encoding options can be passed in the first ``MDString`` operator:
|
|
``<section>!<options>``. The following options are available:
|
|
|
|
* ``C`` -- Compress constant integers of size 2-8 bytes as ULEB128; this
|
|
includes the function size (but excludes the PC entry).
|
|
|
|
For example, ``foo!C`` will emit into section ``foo`` with all constants
|
|
encoded as ULEB128.
|
|
|
|
Guarantees on Code Generation
|
|
=============================
|
|
|
|
Attaching ``!pcsections`` metadata to LLVM IR instructions *shall not* affect
|
|
optimizations or code generation outside the requested PC sections.
|
|
|
|
While relying on LLVM IR metadata to request PC sections makes the above
|
|
guarantee relatively trivial, propagation of metadata through the optimization
|
|
and code generation pipeline has the following guarantees.
|
|
|
|
Metadata Propagation
|
|
--------------------
|
|
|
|
In general, LLVM *does not make any guarantees* about preserving IR metadata
|
|
(attached to an ``Instruction``) through IR transformations. When using PC
|
|
sections metadata, this guarantee is unchanged, and ``!pcsections`` metadata is
|
|
remains *optional* until lowering to machine IR (MIR).
|
|
|
|
Note for Code Generation
|
|
------------------------
|
|
|
|
As with other LLVM IR metadata, there are no requirements for LLVM IR
|
|
transformation passes to preserve ``!pcsections`` metadata, with the following
|
|
exceptions:
|
|
|
|
* The ``AtomicExpandPass`` shall preserve ``!pcsections`` metadata
|
|
according to the below rules 1-4.
|
|
|
|
When translating LLVM IR to MIR, the ``!pcsections`` metadata shall be copied
|
|
from the source ``Instruction`` to the target ``MachineInstr`` (set with
|
|
``MachineInstr::setPCSections()``). The instruction selectors and MIR
|
|
optimization passes shall preserve PC sections metadata as follows:
|
|
|
|
1. Replacements will preserve PC sections metadata of the replaced
|
|
instruction.
|
|
|
|
2. Duplications will preserve PC sections metadata of the copied
|
|
instruction.
|
|
|
|
3. Merging will preserve PC sections metadata of one of the two
|
|
instructions (no guarantee on which instruction's metadata is used).
|
|
|
|
4. Deletions will loose PC sections metadata.
|
|
|
|
This is similar to debug info, and the ``BuildMI()`` helper provides a
|
|
convenient way to propagate debug info and ``!pcsections`` metadata in the
|
|
``MIMetadata`` bundle.
|
|
|
|
Note for Metadata Users
|
|
-----------------------
|
|
|
|
Use cases for ``!pcsections`` metadata should either be fully tolerant to
|
|
missing metadata, or the passes inserting ``!pcsections`` metadata should run
|
|
*after* all LLVM IR optimization passes to preserve the metadata until being
|
|
translated to MIR.
|