[DirectX] PHI Node operand in @llvm.dx.resource.casthandle causing assertion error in DXIL Op Lowering

[Icohedron]

DML shaders of the name ArgOpMultiDimsArg* (16 total) are failing to compile due to an assertion error being triggered by line 181 of DXILOpLowering.cpp.

It appears to be caused by a PHI Node appearing as an operand of @llvm.dx.resource.casthandle.s_dx.types.Handles.tdx.RawBuffer_f16_1_0t

  %35 = phi target("dx.RawBuffer", half, 1, 0) [ %1, %entry.if.end.i_crit_edge ], [ %1, %if.then.i ]
  ...
  %46 = call %dx.types.Handle @llvm.dx.resource.casthandle.s_dx.types.Handles.tdx.RawBuffer_f16_1_0t(target("dx.RawBuffer", half, 1, 0) %35)

This shader used to compile successfully in the past. Running git bisect reveals the first "bad" commit:

87e1da3f2e95fef052e2f7b4167ede0838be24d0 is the first bad commit
commit 87e1da3f2e95fef052e2f7b4167ede0838be24d0
Author: Finn Plummer <mail@inbelic.dev>
Date:   Mon Sep 22 12:18:28 2025 -0700

    [HLSL] Mark `GroupMemoryBarrierWithGroupSync` as `convergent` (#160175)

    `GroupMemoryBarrierWithGroupSync` is required to be marked as convergent
    so that it can't generate duplicate calls or be moved to identical
    control flow.

    Without it, we generate undefined behaviour during optimization. For
    instance: https://godbolt.org/z/9j3vsq1h3.

    Testing that the convergent attribute is added is sufficient. There
    already exists testing,
    [here](https://github.com/inbelic/llvm-project/blob/main/llvm/test/Transforms/SimplifyCFG/attr-convergent.ll),
    that it will not be moved as described in the above link.

clang/lib/Headers/hlsl/hlsl_alias_intrinsics.h                       | 2 +-
clang/test/CodeGenHLSL/builtins/GroupMemoryBarrierWithGroupSync.hlsl | 2 +-
llvm/include/llvm/IR/IntrinsicsDirectX.td                            | 3 ++-
llvm/include/llvm/IR/IntrinsicsSPIRV.td                              | 3 ++-
4 files changed, 6 insertions(+), 4 deletions(-)
bisect found first bad commit

Sample Reproduction

❯ /workspace/llvm-project/build/bin/clang-dxc /mnt/c/workspace/DirectML/Product/Shaders/Generated/ArgOpMultiDimsArgMax_float16_native_accum32_uint32_native_8.hlsl -E CSMain -T cs_6_2  -enable-16bit-types  -O3 -D DXC_COMPILER=1 -D __SHADER_TARGET_MAJOR=6 -D __SHADER_TARGET_MINOR=2 -Vd -I /mnt/c/workspace/DirectML/Product/Shaders/                                            clang-dxc: warning: argument unused during compilation: '-Vd' [-Wunused-command-line-argument]
In file included from /mnt/c/workspace/DirectML/Product/Shaders/Generated/ArgOpMultiDimsArgMax_float16_native_accum32_uint32_native_8.hlsl:51:
In file included from /mnt/c/workspace/DirectML/Product/Shaders/ArgOpMultiDims.hlsl:13:
/mnt/c/workspace/DirectML/Product/Shaders/ShaderIncludes.hlsl:1721:12: warning: 'max<int, 4U>' is deprecated: In 202x mismatched vector/scalar lowering for max is
      deprecated. Explicitly cast parameters. [-Wdeprecated-declarations]
 1721 |     return max(a, s);
      |            ^
/workspace/llvm-project/build/lib/clang/22/include/hlsl/hlsl_compat_overloads.h:404:1: note: 'max<int, 4U>' has been explicitly marked deprecated here
  404 | _DXC_DEPRECATED_VEC_SCALAR_FN(max)
      | ^
/workspace/llvm-project/build/lib/clang/22/include/hlsl/hlsl_compat_overloads.h:28:5: note: expanded from macro '_DXC_DEPRECATED_VEC_SCALAR_FN'
   28 |   [[deprecated("In 202x mismatched vector/scalar lowering for " #fn " is "     \
      |     ^
In file included from /mnt/c/workspace/DirectML/Product/Shaders/Generated/ArgOpMultiDimsArgMax_float16_native_accum32_uint32_native_8.hlsl:51:
In file included from /mnt/c/workspace/DirectML/Product/Shaders/ArgOpMultiDims.hlsl:13:
/mnt/c/workspace/DirectML/Product/Shaders/ShaderIncludes.hlsl:1727:17: warning: 'max<int, 4U>' is deprecated: In 202x mismatched vector/scalar lowering for max is
      deprecated. Explicitly cast parameters. [-Wdeprecated-declarations]
 1727 |     output[0] = max(a[0], s);
      |                 ^
/workspace/llvm-project/build/lib/clang/22/include/hlsl/hlsl_compat_overloads.h:404:1: note: 'max<int, 4U>' has been explicitly marked deprecated here
  404 | _DXC_DEPRECATED_VEC_SCALAR_FN(max)
      | ^
/workspace/llvm-project/build/lib/clang/22/include/hlsl/hlsl_compat_overloads.h:28:5: note: expanded from macro '_DXC_DEPRECATED_VEC_SCALAR_FN'
   28 |   [[deprecated("In 202x mismatched vector/scalar lowering for " #fn " is "     \
      |     ^
In file included from /mnt/c/workspace/DirectML/Product/Shaders/Generated/ArgOpMultiDimsArgMax_float16_native_accum32_uint32_native_8.hlsl:51:
In file included from /mnt/c/workspace/DirectML/Product/Shaders/ArgOpMultiDims.hlsl:13:
/mnt/c/workspace/DirectML/Product/Shaders/ShaderIncludes.hlsl:1728:17: warning: 'max<int, 4U>' is deprecated: In 202x mismatched vector/scalar lowering for max is
      deprecated. Explicitly cast parameters. [-Wdeprecated-declarations]
 1728 |     output[1] = max(a[1], s);
      |                 ^
/workspace/llvm-project/build/lib/clang/22/include/hlsl/hlsl_compat_overloads.h:404:1: note: 'max<int, 4U>' has been explicitly marked deprecated here
  404 | _DXC_DEPRECATED_VEC_SCALAR_FN(max)
      | ^
/workspace/llvm-project/build/lib/clang/22/include/hlsl/hlsl_compat_overloads.h:28:5: note: expanded from macro '_DXC_DEPRECATED_VEC_SCALAR_FN'
   28 |   [[deprecated("In 202x mismatched vector/scalar lowering for " #fn " is "     \
      |     ^
clang-dxc: /workspace/llvm-project/llvm/include/llvm/Support/Casting.h:573: decltype(auto) llvm::cast(From *) [To = llvm::CallInst, From = llvm::Value]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' 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: /workspace/llvm-project/build/bin/clang-dxc /mnt/c/workspace/DirectML/Product/Shaders/Generated/ArgOpMultiDimsArgMax_float16_native_accum32_uint32_native_8.hlsl -E CSMain -T cs_6_2 -enable-16bit-types -O3 -D DXC_COMPILER=1 -D __SHADER_TARGET_MAJOR=6 -D __SHADER_TARGET_MINOR=2 -Vd -I /mnt/c/workspace/DirectML/Product/Shaders/
1.      <eof> parser at end of file
2.      Code generation
3.      Running pass 'DXIL Op Lowering' on module '/mnt/c/workspace/DirectML/Product/Shaders/Generated/ArgOpMultiDimsArgMax_float16_native_accum32_uint32_native_8.hlsl'.
 #0 0x00005a1af7610f2b llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /workspace/llvm-project/llvm/lib/Support/Unix/Signals.inc:834:13
 #1 0x00005a1af760e8c3 llvm::sys::RunSignalHandlers() /workspace/llvm-project/llvm/lib/Support/Signals.cpp:105:18
 #2 0x00005a1af757a9e0 (anonymous namespace)::CrashRecoveryContextImpl::HandleCrash(int, unsigned long) /workspace/llvm-project/llvm/lib/Support/CrashRecoveryContext.cpp:73:5
 #3 0x00005a1af757a9e0 CrashRecoverySignalHandler(int) /workspace/llvm-project/llvm/lib/Support/CrashRecoveryContext.cpp:390:51
 #4 0x00007fbe4e4419c0 __restore_rt (/nix/store/lmn7lwydprqibdkghw7wgcn21yhllz13-glibc-2.40-66/lib/libc.so.6+0x419c0)
 #5 0x00007fbe4e49cf3c __pthread_kill_implementation (/nix/store/lmn7lwydprqibdkghw7wgcn21yhllz13-glibc-2.40-66/lib/libc.so.6+0x9cf3c)
 #6 0x00007fbe4e44190e gsignal (/nix/store/lmn7lwydprqibdkghw7wgcn21yhllz13-glibc-2.40-66/lib/libc.so.6+0x4190e)
 #7 0x00007fbe4e428942 abort (/nix/store/lmn7lwydprqibdkghw7wgcn21yhllz13-glibc-2.40-66/lib/libc.so.6+0x28942)
 #8 0x00007fbe4e42885e _nl_load_domain.cold (/nix/store/lmn7lwydprqibdkghw7wgcn21yhllz13-glibc-2.40-66/lib/libc.so.6+0x2885e)
 #9 0x00007fbe4e4396f7 (/nix/store/lmn7lwydprqibdkghw7wgcn21yhllz13-glibc-2.40-66/lib/libc.so.6+0x396f7)
#10 0x00005a1af62926ee (anonymous namespace)::OpLowerer::lowerIntrinsics() /workspace/llvm-project/llvm/lib/Target/DirectX/DXILOpLowering.cpp:0:0
#11 0x00005a1af62978fd (anonymous namespace)::DXILOpLoweringLegacy::runOnModule(llvm::Module&) /workspace/llvm-project/llvm/lib/Target/DirectX/DXILOpLowering.cpp:994:42
#12 0x00005a1af70b0674 (anonymous namespace)::MPPassManager::runOnModule(llvm::Module&) /workspace/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:0:27
#13 0x00005a1af70b0674 llvm::legacy::PassManagerImpl::run(llvm::Module&) /workspace/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:531:44
#14 0x00005a1af7d5fd50 (anonymous namespace)::EmitAssemblyHelper::RunCodegenPipeline(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>>&) /workspace/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1259:9
#15 0x00005a1af7d5fd50 (anonymous namespace)::EmitAssemblyHelper::emitAssembly(clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>, clang::BackendConsumer*) /workspace/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1282:3
#16 0x00005a1af7d5fd50 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*) /workspace/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1452:13
#17 0x00005a1af7d73a18 std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>::~unique_ptr() /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-gcc-14.3.0/include/c++/14.3.0/bits/unique_ptr.h:398:6
#18 0x00005a1af7d73a18 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) /workspace/llvm-project/clang/lib/CodeGen/CodeGenAction.cpp:312:3
#19 0x00005a1af989e3e9 __gnu_cxx::__normal_iterator<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>*, std::vector<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>, std::allocator<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>>>>::__normal_iterator(std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>* const&) /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-gcc-14.3.0/include/c++/14.3.0/bits/stl_iterator.h:1068:20
#20 0x00005a1af989e3e9 std::vector<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>, std::allocator<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>>>::begin() /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-gcc-14.3.0/include/c++/14.3.0/bits/stl_vector.h:887:16
#21 0x00005a1af989e3e9 void clang::finalize<std::vector<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>, std::allocator<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>>>>(std::vector<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>, std::allocator<std::unique_ptr<clang::TemplateInstantiationCallback, std::default_delete<clang::TemplateInstantiationCallback>>>>&, clang::Sema const&) /workspace/llvm-project/clang/include/clang/Sema/TemplateInstCallback.h:54:16
#22 0x00005a1af989e3e9 clang::ParseAST(clang::Sema&, bool, bool) /workspace/llvm-project/clang/lib/Parse/ParseAST.cpp:190:3
#23 0x00005a1af82b86df clang::HLSLFrontendAction::ExecuteAction() /workspace/llvm-project/clang/lib/Frontend/FrontendActions.cpp:0:35
#24 0x00005a1af827ea57 clang::FrontendAction::Execute() /workspace/llvm-project/clang/lib/Frontend/FrontendAction.cpp:1318:10
#25 0x00005a1af81ea55d llvm::Error::getPtr() const /workspace/llvm-project/llvm/include/llvm/Support/Error.h:278:42
#26 0x00005a1af81ea55d llvm::Error::operator bool() /workspace/llvm-project/llvm/include/llvm/Support/Error.h:241:16
#27 0x00005a1af81ea55d clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) /workspace/llvm-project/clang/lib/Frontend/CompilerInstance.cpp:1007:23
#28 0x00005a1af8373f91 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) /workspace/llvm-project/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp:310:25
#29 0x00005a1af613921a cc1_main(llvm::ArrayRef<char const*>, char const*, void*) /workspace/llvm-project/clang/tools/driver/cc1_main.cpp:300:15
#30 0x00005a1af6135622 ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>) /workspace/llvm-project/clang/tools/driver/driver.cpp:225:12
#31 0x00005a1af61379ec clang_main(int, char**, llvm::ToolContext const&)::$_0::operator()(llvm::SmallVectorImpl<char const*>&) const /workspace/llvm-project/clang/tools/driver/driver.cpp:0:12
#32 0x00005a1af61379ec int llvm::function_ref<int (llvm::SmallVectorImpl<char const*>&)>::callback_fn<clang_main(int, char**, llvm::ToolContext const&)::$_0>(long, llvm::SmallVectorImpl<char const*>&) /workspace/llvm-project/llvm/include/llvm/ADT/STLFunctionalExtras.h:46:12
#33 0x00005a1af805b70e clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*,
bool*) const::$_0::operator()() const /workspace/llvm-project/clang/lib/Driver/Job.cpp:436:30
#34 0x00005a1af805b70e void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::$_0>(long) /workspace/llvm-project/llvm/include/llvm/ADT/STLFunctionalExtras.h:46:12
#35 0x00005a1af757a5d9 llvm::function_ref<void ()>::operator()() const /workspace/llvm-project/llvm/include/llvm/ADT/STLFunctionalExtras.h:0:12
#36 0x00005a1af757a5d9 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) /workspace/llvm-project/llvm/lib/Support/CrashRecoveryContext.cpp:426:3
#37 0x00005a1af805ace9 clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*,bool*) const /workspace/llvm-project/clang/lib/Driver/Job.cpp:436:7
#38 0x00005a1af801be36 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const /workspace/llvm-project/clang/lib/Driver/Compilation.cpp:196:15
#39 0x00005a1af801c0a8 clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const /workspace/llvm-project/clang/lib/Driver/Compilation.cpp:246:13
#40 0x00005a1af8035269 llvm::SmallVectorBase<unsigned int>::empty() const /workspace/llvm-project/llvm/include/llvm/ADT/SmallVector.h:82:46
#41 0x00005a1af8035269 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) /workspace/llvm-project/clang/lib/Driver/Driver.cpp:2244:23
#42 0x00005a1af6134fa3 clang_main(int, char**, llvm::ToolContext const&) /workspace/llvm-project/clang/tools/driver/driver.cpp:407:21
#43 0x00005a1af614512f main /workspace/llvm-project/build/tools/clang/tools/driver/clang-driver.cpp:17:10
#44 0x00007fbe4e42a4d8 __libc_start_call_main (/nix/store/lmn7lwydprqibdkghw7wgcn21yhllz13-glibc-2.40-66/lib/libc.so.6+0x2a4d8)
#45 0x00007fbe4e42a59b __libc_start_main@GLIBC_2.2.5 (/nix/store/lmn7lwydprqibdkghw7wgcn21yhllz13-glibc-2.40-66/lib/libc.so.6+0x2a59b)
#46 0x00005a1af6132f25 _start (/workspace/llvm-project/build/bin/clang-dxc+0x2dd2f25)
clang-dxc: error: clang frontend command failed with exit code 134 (use -v to see invocation)
clang version 22.0.0git (git@github.com:llvm/llvm-project 5843ffb14940920f72516dfe18ed657bee23d1c5)
Target: dxilv1.2-unknown-shadermodel6.2-compute
Thread model: posix
InstalledDir: /workspace/llvm-project/build/bin
Build config: +assertions

I tried using a test case reducer to get a minimal reproduction of the problematic shader code, but even the minimal version is rather large and potentially reveals too much about the original shader source code to publicly share.

[damyanp]

@farzonl to do initial investigation.