inline asm: asm("// %0\n" : "=r"(a) : "0"(a)) crashes on an array variable

[mariete1223]

When compiling the following C++ code that contains inline assembly intended for ARM, Clang crashes with an internal compiler error during instruction selection:

Assertion

clang++: /root/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:530: void getCopyToParts(llvm::SelectionDAG&, const llvm::SDLoc&, llvm::SDValue, llvm::SDValue*, unsigned int, llvm::MVT, const llvm::Value*, std::optional<unsigned int>, llvm::ISD::NodeType): Assertion `NumParts == 1 && "No-op copy with multiple parts!"' failed.

Stack dump

Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -x c++ <source>
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '<source>'.
4.	Running pass 'X86 DAG->DAG Instruction Selection' on function '@main'
 #0 0x0000000003f8ac78 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f8ac78)
 #1 0x0000000003f88904 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f88904)
 #2 0x0000000003ecd6f8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x0000754065042520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007540650969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x0000754065042476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007540650287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x000075406502871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x0000754065039e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x0000000005238227 getCopyToParts(llvm::SelectionDAG&, llvm::SDLoc const&, llvm::SDValue, llvm::SDValue*, unsigned int, llvm::MVT, llvm::Value const*, std::optional<unsigned int>, llvm::ISD::NodeType) SelectionDAGBuilder.cpp:0:0
#10 0x0000000005238409 llvm::RegsForValue::getCopyToRegs(llvm::SDValue, llvm::SelectionDAG&, llvm::SDLoc const&, llvm::SDValue&, llvm::SDValue*, llvm::Value const*, llvm::ISD::NodeType) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5238409)
#11 0x0000000005258810 llvm::SelectionDAGBuilder::visitInlineAsm(llvm::CallBase const&, llvm::BasicBlock const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5258810)
#12 0x000000000527af47 llvm::SelectionDAGBuilder::visitCall(llvm::CallInst const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x527af47)
#13 0x000000000528e76f llvm::SelectionDAGBuilder::visit(llvm::Instruction const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x528e76f)
#14 0x000000000531d3cd llvm::SelectionDAGISel::SelectBasicBlock(llvm::ilist_iterator_w_bits<llvm::ilist_detail::node_options<llvm::Instruction, true, false, void, true, llvm::BasicBlock>, false, true>, llvm::ilist_iterator_w_bits<llvm::ilist_detail::node_options<llvm::Instruction, true, false, void, true, llvm::BasicBlock>, false, true>, bool&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x531d3cd)
#15 0x000000000531e295 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x531e295)
#16 0x000000000531f5d5 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x531f5d5)
#17 0x000000000530fe5f llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x530fe5f)
#18 0x00000000032ad66a llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#19 0x00000000038cfc9f llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x38cfc9f)
#20 0x00000000038d0051 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x38d0051)
#21 0x00000000038d08f1 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x38d08f1)
#22 0x000000000424368e 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+++0x424368e)
#23 0x000000000492f380 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x492f380)
#24 0x000000000660cd6c clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x660cd6c)
#25 0x000000000492f768 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x492f768)
#26 0x0000000004c254a5 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4c254a5)
#27 0x0000000004ba434e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4ba434e)
#28 0x0000000004d191b9 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4d191b9)
#29 0x0000000000da8bdf cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda8bdf)
#30 0x0000000000d9edaa ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#31 0x0000000004996369 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
#32 0x0000000003ecdb94 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ecdb94)
#33 0x000000000499697f 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
#34 0x0000000004958d9d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4958d9d)
#35 0x0000000004959e2e 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+++0x4959e2e)
#36 0x0000000004961c85 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4961c85)
#37 0x0000000000da4b48 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda4b48)
#38 0x0000000000c2a384 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc2a384)
#39 0x0000754065029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#40 0x0000754065029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#41 0x0000000000d9e855 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xd9e855)

Program

#include <iostream>
using namespace std;
int main(void) {
int a[4] = {1,2,3,4};
int b;
int c;
__asm__ __volatile__("ldr %1, [%0, 1] \n"
                     : "=r"(a), "=r"(b)
                     : "0"(a));
}

To reproduce

https://gcc.godbolt.org/z/zahxKxnM1

Generated by fuzzer

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: None (mariete1223)

When compiling the following C++ code that contains inline assembly intended for ARM, Clang crashes with an internal compiler error during instruction selection:

Assertion

clang++: /root/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:530: void getCopyToParts(llvm::SelectionDAG&, const llvm::SDLoc&, llvm::SDValue, llvm::SDValue*, unsigned int, llvm::MVT, const llvm::Value*, std::optional<unsigned int>, llvm::ISD::NodeType): Assertion `NumParts == 1 && "No-op copy with multiple parts!"' failed.

Stack dump

Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -x c++ <source>
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '<source>'.
4.	Running pass 'X86 DAG-&gt;DAG Instruction Selection' on function '@<!-- -->main'
 #<!-- -->0 0x0000000003f8ac78 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f8ac78)
 #<!-- -->1 0x0000000003f88904 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3f88904)
 #<!-- -->2 0x0000000003ecd6f8 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #<!-- -->3 0x0000754065042520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #<!-- -->4 0x00007540650969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #<!-- -->5 0x0000754065042476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #<!-- -->6 0x00007540650287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #<!-- -->7 0x000075406502871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #<!-- -->8 0x0000754065039e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #<!-- -->9 0x0000000005238227 getCopyToParts(llvm::SelectionDAG&amp;, llvm::SDLoc const&amp;, llvm::SDValue, llvm::SDValue*, unsigned int, llvm::MVT, llvm::Value const*, std::optional&lt;unsigned int&gt;, llvm::ISD::NodeType) SelectionDAGBuilder.cpp:0:0
#<!-- -->10 0x0000000005238409 llvm::RegsForValue::getCopyToRegs(llvm::SDValue, llvm::SelectionDAG&amp;, llvm::SDLoc const&amp;, llvm::SDValue&amp;, llvm::SDValue*, llvm::Value const*, llvm::ISD::NodeType) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5238409)
#<!-- -->11 0x0000000005258810 llvm::SelectionDAGBuilder::visitInlineAsm(llvm::CallBase const&amp;, llvm::BasicBlock const*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5258810)
#<!-- -->12 0x000000000527af47 llvm::SelectionDAGBuilder::visitCall(llvm::CallInst const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x527af47)
#<!-- -->13 0x000000000528e76f llvm::SelectionDAGBuilder::visit(llvm::Instruction const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x528e76f)
#<!-- -->14 0x000000000531d3cd llvm::SelectionDAGISel::SelectBasicBlock(llvm::ilist_iterator_w_bits&lt;llvm::ilist_detail::node_options&lt;llvm::Instruction, true, false, void, true, llvm::BasicBlock&gt;, false, true&gt;, llvm::ilist_iterator_w_bits&lt;llvm::ilist_detail::node_options&lt;llvm::Instruction, true, false, void, true, llvm::BasicBlock&gt;, false, true&gt;, bool&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x531d3cd)
#<!-- -->15 0x000000000531e295 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x531e295)
#<!-- -->16 0x000000000531f5d5 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x531f5d5)
#<!-- -->17 0x000000000530fe5f llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x530fe5f)
#<!-- -->18 0x00000000032ad66a llvm::MachineFunctionPass::runOnFunction(llvm::Function&amp;) (.part.0) MachineFunctionPass.cpp:0:0
#<!-- -->19 0x00000000038cfc9f llvm::FPPassManager::runOnFunction(llvm::Function&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x38cfc9f)
#<!-- -->20 0x00000000038d0051 llvm::FPPassManager::runOnModule(llvm::Module&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x38d0051)
#<!-- -->21 0x00000000038d08f1 llvm::legacy::PassManagerImpl::run(llvm::Module&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x38d08f1)
#<!-- -->22 0x000000000424368e clang::emitBackendOutput(clang::CompilerInstance&amp;, clang::CodeGenOptions&amp;, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr&lt;llvm::vfs::FileSystem&gt;, std::unique_ptr&lt;llvm::raw_pwrite_stream, std::default_delete&lt;llvm::raw_pwrite_stream&gt;&gt;, clang::BackendConsumer*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x424368e)
#<!-- -->23 0x000000000492f380 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x492f380)
#<!-- -->24 0x000000000660cd6c clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x660cd6c)
#<!-- -->25 0x000000000492f768 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x492f768)
#<!-- -->26 0x0000000004c254a5 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4c254a5)
#<!-- -->27 0x0000000004ba434e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4ba434e)
#<!-- -->28 0x0000000004d191b9 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4d191b9)
#<!-- -->29 0x0000000000da8bdf cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda8bdf)
#<!-- -->30 0x0000000000d9edaa ExecuteCC1Tool(llvm::SmallVectorImpl&lt;char const*&gt;&amp;, llvm::ToolContext const&amp;) driver.cpp:0:0
#<!-- -->31 0x0000000004996369 void llvm::function_ref&lt;void ()&gt;::callback_fn&lt;clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const::'lambda'()&gt;(long) Job.cpp:0:0
#<!-- -->32 0x0000000003ecdb94 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ecdb94)
#<!-- -->33 0x000000000499697f clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const (.part.0) Job.cpp:0:0
#<!-- -->34 0x0000000004958d9d clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4958d9d)
#<!-- -->35 0x0000000004959e2e clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4959e2e)
#<!-- -->36 0x0000000004961c85 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x4961c85)
#<!-- -->37 0x0000000000da4b48 clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xda4b48)
#<!-- -->38 0x0000000000c2a384 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xc2a384)
#<!-- -->39 0x0000754065029d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#<!-- -->40 0x0000754065029e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#<!-- -->41 0x0000000000d9e855 _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xd9e855)

Program

#include <iostream>
using namespace std;
int main(void) {
int a[4] = {1,2,3,4};
int b;
int c;
__asm__ __volatile__("ldr %1, [%0, 1] \n"
                     : "=r"(a), "=r"(b)
                     : "0"(a));
}

To reproduce

https://gcc.godbolt.org/z/zahxKxnM1

Generated by fuzzer

[brad0]

cc @MaskRay

[MaskRay]

"No-op copy with multiple parts!" when a tied operand has a size (128-bit) larger than the register size (64-bit).

% cat x86.c
int main(void) {
  int a[4] = {1,2,3,4};
  int b;
  asm("// %0\n" : "=r"(a) : "0"(a));
}
% clang -O1 -S x86.c
clang: /home/ray/llvm/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:530: void getCopyToParts(SelectionDAG &, const SDLoc &, SDValue, SDValue *, unsigned int, MVT, const Value *, std::optional<CallingConv::ID>, ISD::NodeType): Assertion `NumParts == 1 && "No-op copy with multi
ple parts!"' failed.
...