[all-commits] [llvm/llvm-project] 7e3735: Reapply [CaptureTracking][FunctionAttrs] Add suppo...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7e3735d1a1b85cea48feb45cb7c2b5d8eaa216ae
      https://github.com/llvm/llvm-project/commit/7e3735d1a1b85cea48feb45cb7c2b5d8eaa216ae
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2025-02-14 (Fri, 14 Feb 2025)

  Changed paths:
    M clang/test/CodeGen/allow-ubsan-check.c
    M clang/test/CodeGenCXX/RelativeVTablesABI/dynamic-cast.cpp
    M clang/test/CodeGenCXX/RelativeVTablesABI/type-info.cpp
    M clang/test/CodeGenOpenCL/amdgcn-buffer-rsrc-type.cl
    M clang/test/CodeGenOpenCL/as_type.cl
    M llvm/include/llvm/Analysis/CaptureTracking.h
    M llvm/include/llvm/IR/InstrTypes.h
    M llvm/include/llvm/Support/ModRef.h
    M llvm/lib/Analysis/AliasAnalysis.cpp
    M llvm/lib/Analysis/CaptureTracking.cpp
    M llvm/lib/Analysis/InstructionSimplify.cpp
    M llvm/lib/IR/Instructions.cpp
    M llvm/lib/Transforms/IPO/AttributorAttributes.cpp
    M llvm/lib/Transforms/IPO/FunctionAttrs.cpp
    M llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
    M llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
    M llvm/test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll
    M llvm/test/Transforms/FunctionAttrs/arg_returned.ll
    M llvm/test/Transforms/FunctionAttrs/nocapture.ll
    M llvm/test/Transforms/FunctionAttrs/nonnull.ll
    M llvm/test/Transforms/FunctionAttrs/noundef.ll
    M llvm/test/Transforms/FunctionAttrs/readattrs.ll
    M llvm/test/Transforms/FunctionAttrs/stats.ll
    M llvm/test/Transforms/PhaseOrdering/AArch64/block_scaling_decompr_8bit.ll
    M llvm/test/Transforms/PhaseOrdering/bitcast-store-branch.ll
    M llvm/test/Transforms/PhaseOrdering/dce-after-argument-promotion-loads.ll
    M llvm/test/Transforms/PhaseOrdering/enable-loop-header-duplication-oz.ll
    M llvm/unittests/Analysis/CaptureTrackingTest.cpp

  Log Message:
  -----------
  Reapply [CaptureTracking][FunctionAttrs] Add support for CaptureInfo (#125880)

Relative to the previous attempt, this adjusts isEscapeSource()
to not treat calls with captures(ret: address, provenance) or similar
arguments as escape sources. This addresses the miscompile reported at:
https://github.com/llvm/llvm-project/pull/125880#issuecomment-2656632577

The implementation uses a helper function on CallBase to make this
check a bit more efficient (e.g. by skipping the byval checks) as
checking attributes on all arguments if fairly expensive.

------

This extends CaptureTracking to support inferring non-trivial
CaptureInfos. The focus of this patch is to only support FunctionAttrs,
other users of CaptureTracking will be updated in followups.

The key API changes here are:

* DetermineUseCaptureKind() now returns a UseCaptureInfo where the UseCC
component specifies what is captured at that Use and the ResultCC
component specifies what may be captured via the return value of the
User. Usually only one or the other will be used (corresponding to
previous MAY_CAPTURE or PASSTHROUGH results), but both may be set for
call captures.
* The CaptureTracking::captures() extension point is passed this
UseCaptureInfo as well and then can decide what to do with it by
returning an Action, which is one of: Stop: stop traversal.
ContinueIgnoringReturn: continue traversal but don't follow the
instruction return value. Continue: continue traversal and follow the
instruction return value if it has additional CaptureComponents.

For now, this patch retains the (unsound) special logic for comparison
of null with a dereferenceable pointer. I'd like to switch key code to
take advantage of address/address_is_null before dropping it.

This PR mainly intends to introduce necessary API changes and basic
inference support, there are various possible improvements marked with
TODOs.



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