`RegisterClassInfo` was supposed to be kept alive between pass runs,
which wasn't being done leading to recomputations increasing the compile
time.
Now the Impl class is a member of the legacy and new passes so that it
is not reconstructed on every pass run.
---------
Co-authored-by: Christudasan Devadasan <christudasan.devadasan@amd.com>
This patch implements an LLVM IR pass, named kernel-info, that reports
various statistics for codes compiled for GPUs. The ultimate goal of
these statistics to help identify bad code patterns and ways to mitigate
them. The pass operates at the LLVM IR level so that it can, in theory,
support any LLVM-based compiler for programming languages supporting
GPUs. It has been tested so far with LLVM IR generated by Clang for
OpenMP offload codes targeting NVIDIA GPUs and AMD GPUs.
By default, the pass runs at the end of LTO, and options like
``-Rpass=kernel-info`` enable its remarks. Example `opt` and `clang`
command lines appear in `llvm/docs/KernelInfo.rst`. Remarks include
summary statistics (e.g., total size of static allocas) and individual
occurrences (e.g., source location of each alloca). Examples of its
output appear in tests in `llvm/test/Analysis/KernelInfo`.
Original commit: eb63cd62a4a1907dbd58f12660efd8244e7d81e9
Previously reverted due to non-negligible compile-time impact in
stage1-ReleaseLTO-g scenario. The issue has been addressed by
always reusing previously computed MemorySSA results, and request
new ones only when `isMemorySSAEnabled` is set.
Co-authored-by: Momchil Velikov <momchil.velikov@arm.com>
This is glue code to convert LowerAllowCheckPass from a FUNCTION_PASS to
FUNCTION_PASS_WITH_PARAMS. The parameters are currently unused.
Future work will plumb `-fsanitize-skip-hot-cutoff` (introduced in
https://github.com/llvm/llvm-project/pull/121619) to
LowerAllowCheckOptions.
And use that as an argument for
allow_ubsan_check when needed.
Other ubsan checks use SanitizerKind,
but those are known to the clang only.
So make it a parameter in LLVM.
#120613 removed -ubsan-unique-traps and replaced it with
-fno-sanitize-merge (introduced in #120511), which allows fine-grained
control of which UBSan checks to prevent merging. This analogous patch
removes -bound-checking-unique-traps, and allows it to be controlled via
-fno-sanitize-merge=local-bounds.
Most of this patch is simply plumbing through the compiler flags into
the bounds checking pass.
Note: this patch subtly changes -fsanitize-merge (the default) to also
include -fsanitize-merge=local-bounds. This is different from the
previous behavior, where -fsanitize-merge (or the old
-ubsan-unique-traps) did not affect local-bounds (requiring the separate
-bounds-checking-unique-traps). However, we argue that the new behavior
is more intuitive.
Removing -bounds-checking-unique-traps and merging its functionality
into -fsanitize-merge breaks backwards compatibility; we hope that this
is acceptable since '-mllvm -bounds-checking-unique-traps' was an
experimental flag.
This was introduced ~5yrs ago (by me), and has never really gotten
any adoption. By now, it's significantly out of sync with new/changed
poison propoagation rules. The idea is still reasonable, but the
imagined use case is largely covered by alive2 these days anyways.
This patch introduces the LLVM components of a type sanitizer: a
sanitizer for type-based aliasing violations.
It is based on Hal Finkel's https://reviews.llvm.org/D32198.
C/C++ have type-based aliasing rules, and LLVM's optimizer can exploit
these given TBAA metadata added by Clang. Roughly, a pointer of given
type cannot be used to access an object of a different type (with, of
course, certain exceptions). Unfortunately, there's a lot of code in the
wild that violates these rules (e.g. for type punning), and such code
often must be built with -fno-strict-aliasing. Performance is often
sacrificed as a result. Part of the problem is the difficulty of finding
TBAA violations. Hopefully, this sanitizer will help.
For each TBAA type-access descriptor, encoded in LLVM's IR using
metadata, the corresponding instrumentation pass generates descriptor
tables. Thus, for each type (and access descriptor), we have a unique
pointer representation. Excepting anonymous-namespace types, these
tables are comdat, so the pointer values should be unique across the
program. The descriptors refer to other descriptors to form a type
aliasing tree (just like LLVM's TBAA metadata does). The instrumentation
handles the "fast path" (where the types match exactly and no
partial-overlaps are detected), and defers to the runtime to handle all
of the more-complicated cases. The runtime, of course, is also
responsible for reporting errors when those are detected.
The runtime uses essentially the same shadow memory region as tsan, and
we use 8 bytes of shadow memory, the size of the pointer to the type
descriptor, for every byte of accessed data in the program. The value 0
is used to represent an unknown type. The value -1 is used to represent
an interior byte (a byte that is part of a type, but not the first
byte). The instrumentation first checks for an exact match between the
type of the current access and the type for that address recorded in the
shadow memory. If it matches, it then checks the shadow for the
remainder of the bytes in the type to make sure that they're all -1. If
not, we call the runtime. If the exact match fails, we next check if the
value is 0 (i.e. unknown). If it is, then we check the shadow for the
remainder of the byes in the type (to make sure they're all 0). If
they're not, we call the runtime. We then set the shadow for the access
address and set the shadow for the remaining bytes in the type to -1
(i.e. marking them as interior bytes). If the type indicated by the
shadow memory for the access address is neither an exact match nor 0, we
call the runtime.
The instrumentation pass inserts calls to the memset intrinsic to set
the memory updated by memset, memcpy, and memmove, as well as
allocas/byval (and for lifetime.start/end) to reset the shadow memory to
reflect that the type is now unknown. The runtime intercepts memset,
memcpy, etc. to perform the same function for the library calls.
The runtime essentially repeats these checks, but uses the full TBAA
algorithm, just as the compiler does, to determine when two types are
permitted to alias. In a situation where access overlap has occurred and
aliasing is not permitted, an error is generated.
Clang's TBAA representation currently has a problem representing unions,
as demonstrated by the one XFAIL'd test in the runtime patch. We'll
update the TBAA representation to fix this, and at the same time, update
the sanitizer.
When the sanitizer is active, we disable actually using the TBAA
metadata for AA. This way we're less likely to use TBAA to remove memory
accesses that we'd like to verify.
As a note, this implementation does not use the compressed shadow-memory
scheme discussed previously
(http://lists.llvm.org/pipermail/llvm-dev/2017-April/111766.html). That
scheme would not handle the struct-path (i.e. structure offset)
information that our TBAA represents. I expect we'll want to further
work on compressing the shadow-memory representation, but I think it
makes sense to do that as follow-up work.
It goes together with the corresponding clang changes
(https://github.com/llvm/llvm-project/pull/76260) and compiler-rt
changes (https://github.com/llvm/llvm-project/pull/76261)
PR: https://github.com/llvm/llvm-project/pull/76259
The existing analysis was already a pimpl wrapper.
I have extracted legacy pass logic to a LDVImpl wrapper named
`LiveDebugVariables` which is the analysis::Result now. This controls
whether to activate the LDV (depending on `-live-debug-variables` and
DIsubprogram) itself.
The legacy and new analysis only construct the LiveDebugVariables.
VirtRegRewriter will test this.
`IRNormalizer` will reorder instructions. Thus, we need to invalidate
analyses. Done in cd500d28cba3177c213f2f2faf50f14ea56e230b. This should
resolve the [BuildBot
failure](https://github.com/llvm/llvm-project/pull/68176#issuecomment-2428243474).
---
Original PR: #68176
Original commit: 1295d2e6da2fe90f3b770ab1d35bf5caecd38bed
Reverted with: 8a12e0131f3d84b470fac63af042aa96a1b19f56
---
Add the llvm-canon tool. Description from the [original
PR](https://reviews.llvm.org/D66029#change-wZv3yOpDdxIu):
> Added a new llvm-canon tool which aims to transform LLVM Modules into
a canonical form by reordering and renaming instructions while
preserving the same semantics. This tool makes it easier to spot
semantic differences while diffing two modules which have undergone
different transformation passes.
The current version of this tool can:
- Reorder instructions within a function.
- Rename instructions based on the operands.
- Sort commutative operands.
This code was originally written by @michalpaszkowski and [submitted to
mainline
LLVM](14d358537f).
However, it was quickly
[reverted](335de55fa3)
to do BuildBot errors.
Michal presented his version of the tool in [LLVM-Canon: Shooting for
Clear Diffs](https://www.youtube.com/watch?v=c9WMijSOEUg).
@AidanGoldfarb and I ported the code to the new pass manager, added more
tests, and fixed some bugs related to PHI nodes that may have been the
root cause of the BuildBot errors that caused the patch to be reverted.
Additionally, we rewrote the implementation of instruction reordering to
fix cases where the original algorithm would break use-def chains.
Note that this is @AidanGoldfarb and I's first time submitting to LLVM.
Please liberally critique the PR!
CC @plotfi for initial review.
---------
Co-authored-by: Aidan <aidan.goldfarb@mail.mcgill.ca>
This implements a global function merging pass. Unlike traditional
function merging passes that use IR comparators, this pass employs a
structurally stable hash to identify similar functions while ignoring
certain constant operands. These ignored constants are tracked and
encoded into a stable function summary. When merging, instead of
explicitly folding similar functions and their call sites, we form a
merging instance by supplying different parameters via thunks. The
actual size reduction occurs when identically created merging instances
are folded by the linker.
Currently, this pass is wired to a pre-codegen pass, enabled by the
`-enable-global-merge-func` flag.
In a local merging mode, the analysis and merging steps occur
sequentially within a module:
- `analyze`: Collects stable function hashes and tracks locations of
ignored constant operands.
- `finalize`: Identifies merge candidates with matching hashes and
computes the set of parameters that point to different constants.
- `merge`: Uses the stable function map to optimistically create a
merged function.
We can enable a global merging mode similar to the global function
outliner
(https://discourse.llvm.org/t/rfc-enhanced-machine-outliner-part-2-thinlto-nolto/78753/),
which will perform the above steps separately.
- `-codegen-data-generate`: During the first round of code generation,
we analyze local merging instances and publish their summaries.
- Offline using `llvm-cgdata` or at link-time, we can finalize all these
merging summaries that are combined to determine parameters.
- `-codegen-data-use`: During the second round of code generation, we
optimistically create merging instances within each module, and finally,
the linker folds identically created merging instances.
Depends on #112664
This is a patch for
https://discourse.llvm.org/t/rfc-global-function-merging/82608.
This reverts commit c31014322c0b5ae596da129cbb844fb2198b4ef4.
Based on the discussions in #112772, this pass is not needed after the
introduction of `llvm.threadlocal.address` intrinsic.
Fixes https://github.com/llvm/llvm-project/issues/112771.
This computes a structural hash while allowing for selective ignoring of
certain operands based on a custom function that is provided. Instead of
a single hash value, it now returns FunctionHashInfo which includes a
hash value, an instruction mapping, and a map to track the operand
location and its corresponding hash value that is ignored.
Depends on https://github.com/llvm/llvm-project/pull/112621.
This is a patch for
https://discourse.llvm.org/t/rfc-global-function-merging/82608.
Add the llvm-canon tool. Description from the [original
PR](https://reviews.llvm.org/D66029#change-wZv3yOpDdxIu):
> Added a new llvm-canon tool which aims to transform LLVM Modules into
a canonical form by reordering and renaming instructions while
preserving the same semantics. This tool makes it easier to spot
semantic differences while diffing two modules which have undergone
different transformation passes.
The current version of this tool can:
- Reorder instructions within a function.
- Rename instructions based on the operands.
- Sort commutative operands.
This code was originally written by @michalpaszkowski and [submitted to
mainline
LLVM](14d358537f).
However, it was quickly
[reverted](335de55fa3)
to do BuildBot errors.
Michal presented his version of the tool in [LLVM-Canon: Shooting for
Clear Diffs](https://www.youtube.com/watch?v=c9WMijSOEUg).
@AidanGoldfarb and I ported the code to the new pass manager, added more
tests, and fixed some bugs related to PHI nodes that may have been the
root cause of the BuildBot errors that caused the patch to be reverted.
Additionally, we rewrote the implementation of instruction reordering to
fix cases where the original algorithm would break use-def chains.
Note that this is @AidanGoldfarb and I's first time submitting to LLVM.
Please liberally critique the PR!
CC @plotfi for initial review.
---------
Co-authored-by: Aidan <aidan.goldfarb@mail.mcgill.ca>
