[llvm] [VPlan] Add transform to replace VPWidenCanonicalIV with wide IV. (PR #194267)

Wed Apr 29 13:06:11 PDT 2026

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-expensive-checks-ubuntu` running on `as-builder-4` while building `llvm` at step 7 "test-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/187/builds/19595

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 7 (test-check-all) failure: Test just built components: check-all completed (failure)
******************** TEST 'LLVM :: Transforms/LoopVectorize/pr43166-fold-tail-by-masking.ll' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 2
/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt < /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/test/Transforms/LoopVectorize/pr43166-fold-tail-by-masking.ll -passes=loop-vectorize -force-vector-width=4 -S | /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/FileCheck /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/test/Transforms/LoopVectorize/pr43166-fold-tail-by-masking.ll
# executed command: /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt -passes=loop-vectorize -force-vector-width=4 -S
# .---command stderr------------
# | LastActiveLane operand vp<%11> must be prefix mask (a header mask or an EVL-derived mask currently)
# | LLVM ERROR: Broken VPlan found, compilation aborted!
# | PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
# | Stack dump:
# | 0.	Program arguments: /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt -passes=loop-vectorize -force-vector-width=4 -S
# | 1.	Running pass "function(loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>)" on module "<stdin>"
# | 2.	Running pass "loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>" on function "test1"
# |  #0 0x0000640a394b0998 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x5233998)
# |  #1 0x0000640a394ad7b1 llvm::sys::RunSignalHandlers() (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x52307b1)
# |  #2 0x0000640a394b1b31 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
# |  #3 0x000078d95cc45330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
# |  #4 0x000078d95cc9eb2c pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x9eb2c)
# |  #5 0x000078d95cc4527e raise (/lib/x86_64-linux-gnu/libc.so.6+0x4527e)
# |  #6 0x000078d95cc288ff abort (/lib/x86_64-linux-gnu/libc.so.6+0x288ff)
# |  #7 0x0000640a39475af5 llvm::report_fatal_error(llvm::Twine const&, bool) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x51f8af5)
# |  #8 0x0000640a39475936 (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x51f8936)
# |  #9 0x0000640a3ab6c2cd (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x68ef2cd)
# | #10 0x0000640a3ab42b63 llvm::LoopVectorizationPlanner::executePlan(llvm::ElementCount, unsigned int, llvm::VPlan&, llvm::InnerLoopVectorizer&, llvm::DominatorTree*, llvm::LoopVectorizationPlanner::EpilogueVectorizationKind) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x68c5b63)
# | #11 0x0000640a3ab4fb0d llvm::LoopVectorizePass::processLoop(llvm::Loop*) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x68d2b0d)
# | #12 0x0000640a3ab58f7b llvm::LoopVectorizePass::runImpl(llvm::Function&) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x68dbf7b)
# | #13 0x0000640a3ab59824 llvm::LoopVectorizePass::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x68dc824)
# | #14 0x0000640a3aa19a9d llvm::detail::PassModel<llvm::Function, llvm::LoopVectorizePass, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) PassBuilderPipelines.cpp:0:0
# | #15 0x0000640a396d6f87 llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x5459f87)
# | #16 0x0000640a3aa1708d llvm::detail::PassModel<llvm::Function, llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) PassBuilderPipelines.cpp:0:0
# | #17 0x0000640a396db9d1 llvm::ModuleToFunctionPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x545e9d1)
# | #18 0x0000640a3a9a6f7d llvm::detail::PassModel<llvm::Module, llvm::ModuleToFunctionPassAdaptor, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) NewPMDriver.cpp:0:0
# | #19 0x0000640a396d5d47 llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x5458d47)
# | #20 0x0000640a3a99f402 llvm::runPassPipeline(llvm::StringRef, llvm::Module&, llvm::TargetMachine*, llvm::TargetLibraryInfoImpl*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::StringRef, llvm::ArrayRef<llvm::PassPlugin>, llvm::ArrayRef<std::function<void (llvm::PassBuilder&)>>, llvm::opt_tool::OutputKind, llvm::opt_tool::VerifierKind, bool, bool, bool, bool, bool, bool, bool, bool) (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x6722402)
# | #21 0x0000640a3944ec68 optMain (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x51d1c68)
# | #22 0x000078d95cc2a1ca (/lib/x86_64-linux-gnu/libc.so.6+0x2a1ca)
# | #23 0x000078d95cc2a28b __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2a28b)
# | #24 0x0000640a39448725 _start (/home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/opt+0x51cb725)
# `-----------------------------
# error: command failed with exit status: -6
# executed command: /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/FileCheck /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/test/Transforms/LoopVectorize/pr43166-fold-tail-by-masking.ll
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/build/bin/FileCheck /home/buildbot/worker/as-builder-4/ramdisk/expensive-checks/llvm-project/llvm/test/Transforms/LoopVectorize/pr43166-fold-tail-by-masking.ll
# `-----------------------------
# error: command failed with exit status: 2

...

```

</details>

https://github.com/llvm/llvm-project/pull/194267