[llvm] [VPlan] Treat VPVector(End)PointerRecipe as single-scalar, if ops are. (PR #169249)
Alexander Kornienko via llvm-commits
llvm-commits at lists.llvm.org
Sun Nov 30 16:17:35 PST 2025
alexfh wrote:
Hi @fhahn, this seems to trigger assertion failures in Clang: https://gcc.godbolt.org/z/87jE85Tdq
```
clang++: /root/llvm-project/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:7205: llvm::VectorizationFactor llvm::LoopVectorizationPlanner::computeBestVF(): Assertion `(BestFactor.Width == LegacyVF.Width || BestPlan.hasEarlyExit() || !Legal->getLAI()->getSymbolicStrides().empty() || UsesEVLGatherScatter || planContainsAdditionalSimplifications( getPlanFor(BestFactor.Width), CostCtx, OrigLoop, BestFactor.Width) || planContainsAdditionalSimplifications( getPlanFor(LegacyVF.Width), CostCtx, OrigLoop, LegacyVF.Width)) && " VPlan cost model and legacy cost model disagreed"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0. Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang++ -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fverbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -xir -O3 <source>
1. Optimizer
2. Running pass "function<eager-inv>(drop-unnecessary-assumes,float2int,lower-constant-intrinsics,chr,loop(loop-rotate<header-duplication;no-prepare-for-lto>,loop-deletion),loop-distribute,inject-tli-mappings,loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>,drop-unnecessary-assumes,infer-alignment,loop-load-elim,instcombine<max-iterations=1;no-verify-fixpoint>,simplifycfg<bonus-inst-threshold=1;forward-switch-cond;switch-range-to-icmp;switch-to-arithmetic;switch-to-lookup;no-keep-loops;hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>,slp-vectorizer,vector-combine,instcombine<max-iterations=1;no-verify-fixpoint>,loop-unroll<O3>,transform-warning,sroa<preserve-cfg>,infer-alignment,instcombine<max-iterations=1;no-verify-fixpoint>,loop-mssa(licm<allowspeculation>),alignment-from-assumptions,loop-sink,instsimplify,div-rem-pairs,tailcallelim,simplifycfg<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;switch-to-arithmetic;no-switch-to-lookup;keep-loops;no-hoist-common-insts;hoist-loads-stores-with-cond-faulting;no-sink-common-insts;speculate-blocks;simplify-cond-branch;speculate-unpredictables>)" on module "<source>"
3. Running pass "loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>" on function "eggs"
#0 0x0000000004279728 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4279728)
#1 0x0000000004276b54 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4276b54)
#2 0x00000000041ba888 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
#3 0x00007d8f25c42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
#4 0x00007d8f25c969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
#5 0x00007d8f25c42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
#6 0x00007d8f25c287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
#7 0x00007d8f25c2871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
#8 0x00007d8f25c39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
#9 0x0000000005dff188 llvm::LoopVectorizationPlanner::computeBestVF() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5dff188)
#10 0x0000000005e0134c llvm::LoopVectorizePass::processLoop(llvm::Loop*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5e0134c)
#11 0x0000000005e03f10 llvm::LoopVectorizePass::runImpl(llvm::Function&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5e03f10)
#12 0x0000000005e0463b llvm::LoopVectorizePass::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5e0463b)
#13 0x0000000005447e9e llvm::detail::PassModel<llvm::Function, llvm::LoopVectorizePass, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5447e9e)
#14 0x0000000003bcba31 llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bcba31)
#15 0x000000000126188e llvm::detail::PassModel<llvm::Function, llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x126188e)
#16 0x0000000003bca0fa llvm::ModuleToFunctionPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bca0fa)
#17 0x0000000001261b7e llvm::detail::PassModel<llvm::Module, llvm::ModuleToFunctionPassAdaptor, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x1261b7e)
#18 0x0000000003bc9ab1 llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3bc9ab1)
#19 0x0000000004534203 (anonymous namespace)::EmitAssemblyHelper::RunOptimizationPipeline(clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>&, std::unique_ptr<llvm::ToolOutputFile, std::default_delete<llvm::ToolOutputFile>>&, clang::BackendConsumer*) BackendUtil.cpp:0:0
#20 0x00000000045378d9 clang::emitBackendOutput(clang::CompilerInstance&, clang::CodeGenOptions&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>, clang::BackendConsumer*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x45378d9)
#21 0x0000000004bc947f clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4bc947f)
#22 0x0000000004eb4455 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4eb4455)
#23 0x0000000004e3460e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4e3460e)
#24 0x0000000004fad48d clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4fad48d)
#25 0x0000000000dc7780 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdc7780)
#26 0x0000000000dbe1fa ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>) driver.cpp:0:0
#27 0x0000000000dbe37d int llvm::function_ref<int (llvm::SmallVectorImpl<char const*>&)>::callback_fn<clang_main(int, char**, llvm::ToolContext const&)::'lambda'(llvm::SmallVectorImpl<char const*>&)>(long, llvm::SmallVectorImpl<char const*>&) driver.cpp:0:0
#28 0x0000000004c313d9 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#29 0x00000000041bad24 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x41bad24)
#30 0x0000000004c319ef clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (.part.0) Job.cpp:0:0
#31 0x0000000004bf21e2 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4bf21e2)
#32 0x0000000004bf318e clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4bf318e)
#33 0x0000000004bfa5c5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4bfa5c5)
#34 0x0000000000dc3ba1 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdc3ba1)
#35 0x0000000000c72574 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc72574)
#36 0x00007d8f25c29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#37 0x00007d8f25c29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#38 0x0000000000dbdc95 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xdbdc95)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
```
A reduced test case:
```
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%struct.foo.7 = type <{ %struct.eggs, i32, [4 x i8] }>
%struct.eggs = type { ptr, i64 }
%struct.wibble = type { ptr, i64 }
define ptr @foo(ptr %arg, i64 %arg1) {
bb:
%alloca = alloca i64, align 8
store i64 %arg1, ptr %alloca, align 8
%load = load ptr, ptr %arg, align 8
%load2 = load i64, ptr %alloca, align 8
%getelementptr = getelementptr i8, ptr %load, i64 %load2
ret ptr %getelementptr
}
define ptr @ham(ptr %arg) {
bb:
store ptr @wombat, ptr %arg, align 8
ret ptr null
}
declare ptr @wombat()
define i64 @eggs(ptr %arg) {
bb:
%alloca = alloca i32, align 4
store i32 0, ptr %alloca, align 4
br label %bb1
bb1: ; preds = %bb3, %bb
%load = load i32, ptr %alloca, align 4
%icmp = icmp slt i32 %load, 32
br i1 %icmp, label %bb3, label %bb2
bb2: ; preds = %bb1
ret i64 0
bb3: ; preds = %bb1
%load4 = load i32, ptr %alloca, align 4
store i32 %load4, ptr %arg, align 4
%load5 = load i32, ptr %arg, align 4
%call = call ptr @barney(ptr %arg, i32 %load5)
%load6 = load i32, ptr %alloca, align 4
%add = add i32 %load6, 1
store i32 %add, ptr %alloca, align 4
br label %bb1
}
define ptr @barney(ptr %arg, i32 %arg1) {
bb:
%alloca = alloca %struct.foo.7, align 8
%mul = mul i32 %arg1, 128
store ptr %alloca, ptr %arg, align 8
%load = load ptr, ptr %arg, align 8
%getelementptr = getelementptr %struct.foo.7, ptr %load, i32 0, i32 1
store i32 %mul, ptr %getelementptr, align 8
%call = call ptr @bar(ptr %arg, ptr %alloca)
ret ptr %call
; uselistorder directives
uselistorder ptr %arg, { 2, 1, 0 }
}
define ptr @bar(ptr noalias %arg, ptr %arg1) {
bb:
call void @wombat.1(ptr %arg, ptr %arg1)
ret ptr null
}
define void @wombat.1(ptr %arg, ptr %arg1) {
bb:
%alloca = alloca i32, align 4
store i32 0, ptr %alloca, align 4
br label %bb2
bb2: ; preds = %bb4, %bb
%load = load i32, ptr %alloca, align 4
%icmp = icmp slt i32 %load, 64
br i1 %icmp, label %bb4, label %bb3
bb3: ; preds = %bb2
ret void
bb4: ; preds = %bb2
%load5 = load i32, ptr %alloca, align 4
%call = call i1 @barney.2(ptr %arg1, i32 %load5)
%load6 = load i32, ptr %alloca, align 4
%sext = sext i32 %load6 to i64
%call7 = call ptr @snork(ptr %arg, i64 %sext)
%zext = zext i1 %call to i8
store i8 %zext, ptr %call7, align 1
%load8 = load i32, ptr %alloca, align 4
%add = add i32 %load8, 1
store i32 %add, ptr %alloca, align 4
br label %bb2
}
define i1 @barney.2(ptr %arg, i32 %arg1) {
bb:
%alloca = alloca ptr, align 8
%alloca2 = alloca %struct.wibble, align 8
store ptr %arg, ptr %arg, align 8
%load = load ptr, ptr %arg, align 8
%getelementptr = getelementptr %struct.foo.7, ptr %load, i32 0, i32 1
%load3 = load i32, ptr %getelementptr, align 8
%add = add i32 %load3, %arg1
store i32 %add, ptr %arg, align 4
%call = call ptr @ham(ptr %alloca2)
call void @pluto(ptr %alloca2, ptr %arg)
%load4 = load i8, ptr %arg, align 1
%trunc = trunc i8 %load4 to i1
ret i1 %trunc
}
define ptr @snork(ptr %arg, i64 %arg1) {
bb:
%alloca = alloca ptr, align 8
%alloca2 = alloca i64, align 8
store ptr %arg, ptr %alloca, align 8
store i64 %arg1, ptr %alloca2, align 8
%load = load ptr, ptr %alloca, align 8
%load3 = load i64, ptr %alloca2, align 8
%getelementptr = getelementptr [64 x i8], ptr %load, i64 0, i64 %load3
ret ptr %getelementptr
}
define void @pluto(ptr %arg, ptr %arg1) {
bb:
%alloca = alloca i32, align 4
%load = load i32, ptr %arg1, align 4
%sdiv = sdiv i32 %load, 8
store i32 %sdiv, ptr %alloca, align 4
%load2 = load i32, ptr %alloca, align 4
%sext = sext i32 %load2 to i64
%call = call ptr @foo(ptr %arg, i64 %sext)
%load3 = load i8, ptr %call, align 1
store i8 %load3, ptr %arg, align 1
%load4 = load i8, ptr %arg, align 1
store i8 %load4, ptr %arg1, align 1
ret void
}
```
https://github.com/llvm/llvm-project/pull/169249
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