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JustinKim98 opened this issue Apr 15, 2025 · 3 comments · Fixed by #135838
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[clang][llc][AArch64] Instruction selection failure when targeting aarch64 architecture with 16bit vector types #135776

JustinKim98 opened this issue Apr 15, 2025 · 3 comments · Fixed by #135838
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crash Prefer [crash-on-valid] or [crash-on-invalid] llvm:SelectionDAG SelectionDAGISel as well

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@JustinKim98
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JustinKim98 commented Apr 15, 2025 •
edited by davemgreen
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While I was trying to cross-compile following llvm IR bit cast using llc with following command in debug mode towards aarch64 architecture.

llc example.ll --mtriple=aarch64-linux-gnu -o example.s

(LLVM IR I'm trying to compile)
https://godbolt.org/z/Ejzcj6GY9

; example.ll
target triple = "aarch64-unknown-linux-gnu"

define i32 @bitcast_failure(ptr %0, <1 x i16> %1) {
  %3 = bitcast <1 x i16> %1 to <1 x half>
  %4 = extractelement <1 x half> %3, i64 0
  store half %4, ptr %0, align 2
  ret i32 0
}

I'm encountering some kind of weird error. Is this a bug in LLVM? It seems like there's a problem when trying to scalarize 16 bit data types.
I'm using the newest llvm version that I just cloned from main branch.

# llc --version
LLVM (http://llvm.org/):
  LLVM version 21.0.0git
  DEBUG build with assertions.
  Default target: x86_64-unknown-linux-gnu
  Host CPU: znver4

Is this a bug in LLVM? or am I doing something wrong?

Here's the error log

llc: /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h:161: const llvm::SDValue& llvm::DAGTypeLegalizer::getSDValue(llvm::DAGTypeLegalizer::TableId&): Assertion `Id && "TableId should be non-zero"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: ./llvm-build-debug/bin/llc example2.ll --mtriple=aarch64-linux-gnu
1.	Running pass 'Function Pass Manager' on module 'example2.ll'.
2.	Running pass 'AArch64 Instruction Selection' on function '@bitcast_failure'
 #0 0x000064116e051396 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/jwkim98/llvm_test/llvm-project/llvm/lib/Support/Unix/Signals.inc:804:22
 #1 0x000064116e0517b7 PrintStackTraceSignalHandler(void*) /home/jwkim98/llvm_test/llvm-project/llvm/lib/Support/Unix/Signals.inc:880:1
 #2 0x000064116e04ebe5 llvm::sys::RunSignalHandlers() /home/jwkim98/llvm_test/llvm-project/llvm/lib/Support/Signals.cpp:105:20
 #3 0x000064116e050c05 SignalHandler(int, siginfo_t*, void*) /home/jwkim98/llvm_test/llvm-project/llvm/lib/Support/Unix/Signals.inc:418:13
 #4 0x0000782303a42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #5 0x0000782303a969fc __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #6 0x0000782303a969fc __pthread_kill_internal ./nptl/pthread_kill.c:78:10
 #7 0x0000782303a969fc pthread_kill ./nptl/pthread_kill.c:89:10
 #8 0x0000782303a42476 gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #9 0x0000782303a287f3 abort ./stdlib/abort.c:81:7
#10 0x0000782303a2871b _nl_load_domain ./intl/loadmsgcat.c:1177:9
#11 0x0000782303a39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
#12 0x000064116de34302 llvm::DAGTypeLegalizer::getSDValue(unsigned int&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h:162:31
#13 0x000064116de92ad3 llvm::DAGTypeLegalizer::GetScalarizedVector(llvm::SDValue) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h:851:51
#14 0x000064116de53763 llvm::DAGTypeLegalizer::ScalarizeVecRes_BITCAST(llvm::SDNode*) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp:406:29
#15 0x000064116de51b47 llvm::DAGTypeLegalizer::ScalarizeVectorResult(llvm::SDNode*, unsigned int) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp:57:59
#16 0x000064116de2eeaa llvm::DAGTypeLegalizer::run() /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp:281:17
#17 0x000064116de33624 llvm::SelectionDAG::LegalizeTypes() /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp:1060:37
#18 0x000064116dd8250e llvm::SelectionDAGISel::CodeGenAndEmitDAG() /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:979:36
#19 0x000064116dd81a23 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&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:877:1
#20 0x000064116dd878ed llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:1906:33
#21 0x000064116dd8010b llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:615:7
#22 0x0000641169bb141a (anonymous namespace)::AArch64DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp:61:0
#23 0x000064116dd7ee62 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:374:40
#24 0x000064116c98b2dc llvm::MachineFunctionPass::runOnFunction(llvm::Function&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/MachineFunctionPass.cpp:108:30
#25 0x000064116d248162 llvm::FPPassManager::runOnFunction(llvm::Function&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1406:20
#26 0x000064116d248438 llvm::FPPassManager::runOnModule(llvm::Module&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1452:13
#27 0x000064116d248899 (anonymous namespace)::MPPassManager::runOnModule(llvm::Module&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1521:20
#28 0x000064116d2438e1 llvm::legacy::PassManagerImpl::run(llvm::Module&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:539:13
#29 0x000064116d24918f llvm::legacy::PassManager::run(llvm::Module&) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1649:1
#30 0x000064116955118a compileModule(char**, llvm::LLVMContext&) /home/jwkim98/llvm_test/llvm-project/llvm/tools/llc/llc.cpp:755:34
#31 0x000064116954e810 main /home/jwkim98/llvm_test/llvm-project/llvm/tools/llc/llc.cpp:400:35
#32 0x0000782303a29d90 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#33 0x0000782303a29e40 call_init ./csu/../csu/libc-start.c:128:20
#34 0x0000782303a29e40 __libc_start_main ./csu/../csu/libc-start.c:379:5
#35 0x000064116954d3e5 _start (./llvm-build-debug/bin/llc+0xf613e5)
Aborted
@JustinKim98 JustinKim98 changed the title Instruction selection failure when targetting aarch64 architecture with 16bit vector types [clang] Instruction selection failure when targetting aarch64 architecture with 16bit vector types Apr 15, 2025
@JustinKim98 JustinKim98 changed the title [clang] Instruction selection failure when targetting aarch64 architecture with 16bit vector types Instruction selection failure when targetting aarch64 architecture with 16bit vector types Apr 15, 2025
@JustinKim98 JustinKim98 changed the title Instruction selection failure when targetting aarch64 architecture with 16bit vector types [clang] Instruction selection failure when targetting aarch64 architecture with 16bit vector types Apr 15, 2025
@JustinKim98 JustinKim98 changed the title [clang] Instruction selection failure when targetting aarch64 architecture with 16bit vector types [clang][llc] Instruction selection failure when targetting aarch64 architecture with 16bit vector types Apr 15, 2025
@JustinKim98 JustinKim98 changed the title [clang][llc] Instruction selection failure when targetting aarch64 architecture with 16bit vector types [clang][llc] Instruction selection failure when targeting aarch64 architecture with 16bit vector types Apr 15, 2025
@JustinKim98 JustinKim98 changed the title [clang][llc] Instruction selection failure when targeting aarch64 architecture with 16bit vector types [clang][llc][AArch64] Instruction selection failure when targeting aarch64 architecture with 16bit vector types Apr 15, 2025
@EugeneZelenko EugeneZelenko added backend:AArch64 crash Prefer [crash-on-valid] or [crash-on-invalid] and removed new issue labels Apr 15, 2025
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llvmbot commented Apr 15, 2025

@llvm/issue-subscribers-backend-aarch64

Author: Justin Kim (JustinKim98)

While I was trying to cross-compile following llvm IR bit cast using llc with following command in debug mode towards aarch64 architecture. 
llc example.ll --mtriple=aarch64-linux-gnu -o example.s

(LLVM IR I'm trying to compile)

; example.ll
target triple = "aarch64-unknown-linux-gnu"

define i32 @<!-- -->bitcast_failure(ptr %0, &lt;1 x i16&gt; %1) {
  %3 = bitcast &lt;1 x i16&gt; %1 to &lt;1 x half&gt;
  %4 = extractelement &lt;1 x half&gt; %3, i64 0
  store half %4, ptr %0, align 2
  ret i32 0
}

I'm encountering some kind of weird error. Is this a bug in LLVM? It seems like there's a problem when trying to scalarize 16 bit data types.
I'm using the newest llvm version that I just cloned from main branch.

# llc --version
LLVM (http://llvm.org/):
  LLVM version 21.0.0git
  DEBUG build with assertions.
  Default target: x86_64-unknown-linux-gnu
  Host CPU: znver4

Is this a bug in LLVM? or am I doing something wrong?

Here's the error log

llc: /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h:161: const llvm::SDValue&amp; llvm::DAGTypeLegalizer::getSDValue(llvm::DAGTypeLegalizer::TableId&amp;): Assertion `Id &amp;&amp; "TableId should be non-zero"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: ./llvm-build-debug/bin/llc example2.ll --mtriple=aarch64-linux-gnu
1.	Running pass 'Function Pass Manager' on module 'example2.ll'.
2.	Running pass 'AArch64 Instruction Selection' on function '@<!-- -->bitcast_failure'
 #<!-- -->0 0x000064116e051396 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) /home/jwkim98/llvm_test/llvm-project/llvm/lib/Support/Unix/Signals.inc:804:22
 #<!-- -->1 0x000064116e0517b7 PrintStackTraceSignalHandler(void*) /home/jwkim98/llvm_test/llvm-project/llvm/lib/Support/Unix/Signals.inc:880:1
 #<!-- -->2 0x000064116e04ebe5 llvm::sys::RunSignalHandlers() /home/jwkim98/llvm_test/llvm-project/llvm/lib/Support/Signals.cpp:105:20
 #<!-- -->3 0x000064116e050c05 SignalHandler(int, siginfo_t*, void*) /home/jwkim98/llvm_test/llvm-project/llvm/lib/Support/Unix/Signals.inc:418:13
 #<!-- -->4 0x0000782303a42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #<!-- -->5 0x0000782303a969fc __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #<!-- -->6 0x0000782303a969fc __pthread_kill_internal ./nptl/pthread_kill.c:78:10
 #<!-- -->7 0x0000782303a969fc pthread_kill ./nptl/pthread_kill.c:89:10
 #<!-- -->8 0x0000782303a42476 gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #<!-- -->9 0x0000782303a287f3 abort ./stdlib/abort.c:81:7
#<!-- -->10 0x0000782303a2871b _nl_load_domain ./intl/loadmsgcat.c:1177:9
#<!-- -->11 0x0000782303a39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
#<!-- -->12 0x000064116de34302 llvm::DAGTypeLegalizer::getSDValue(unsigned int&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h:162:31
#<!-- -->13 0x000064116de92ad3 llvm::DAGTypeLegalizer::GetScalarizedVector(llvm::SDValue) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h:851:51
#<!-- -->14 0x000064116de53763 llvm::DAGTypeLegalizer::ScalarizeVecRes_BITCAST(llvm::SDNode*) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp:406:29
#<!-- -->15 0x000064116de51b47 llvm::DAGTypeLegalizer::ScalarizeVectorResult(llvm::SDNode*, unsigned int) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp:57:59
#<!-- -->16 0x000064116de2eeaa llvm::DAGTypeLegalizer::run() /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp:281:17
#<!-- -->17 0x000064116de33624 llvm::SelectionDAG::LegalizeTypes() /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp:1060:37
#<!-- -->18 0x000064116dd8250e llvm::SelectionDAGISel::CodeGenAndEmitDAG() /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:979:36
#<!-- -->19 0x000064116dd81a23 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;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:877:1
#<!-- -->20 0x000064116dd878ed llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:1906:33
#<!-- -->21 0x000064116dd8010b llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:615:7
#<!-- -->22 0x0000641169bb141a (anonymous namespace)::AArch64DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp:61:0
#<!-- -->23 0x000064116dd7ee62 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:374:40
#<!-- -->24 0x000064116c98b2dc llvm::MachineFunctionPass::runOnFunction(llvm::Function&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/CodeGen/MachineFunctionPass.cpp:108:30
#<!-- -->25 0x000064116d248162 llvm::FPPassManager::runOnFunction(llvm::Function&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1406:20
#<!-- -->26 0x000064116d248438 llvm::FPPassManager::runOnModule(llvm::Module&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1452:13
#<!-- -->27 0x000064116d248899 (anonymous namespace)::MPPassManager::runOnModule(llvm::Module&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1521:20
#<!-- -->28 0x000064116d2438e1 llvm::legacy::PassManagerImpl::run(llvm::Module&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:539:13
#<!-- -->29 0x000064116d24918f llvm::legacy::PassManager::run(llvm::Module&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1649:1
#<!-- -->30 0x000064116955118a compileModule(char**, llvm::LLVMContext&amp;) /home/jwkim98/llvm_test/llvm-project/llvm/tools/llc/llc.cpp:755:34
#<!-- -->31 0x000064116954e810 main /home/jwkim98/llvm_test/llvm-project/llvm/tools/llc/llc.cpp:400:35
#<!-- -->32 0x0000782303a29d90 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#<!-- -->33 0x0000782303a29e40 call_init ./csu/../csu/libc-start.c:128:20
#<!-- -->34 0x0000782303a29e40 __libc_start_main ./csu/../csu/libc-start.c:379:5
#<!-- -->35 0x000064116954d3e5 _start (./llvm-build-debug/bin/llc+0xf613e5)
Aborted

@topperc topperc self-assigned this Apr 15, 2025
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topperc commented Apr 15, 2025

I see the problem and I'm working on a fix.

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topperc commented Apr 15, 2025

This should fix it

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index f934d8b37561..a01e1cff7456 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -400,9 +400,7 @@ SDValue DAGTypeLegalizer::ScalarizeVecRes_MERGE_VALUES(SDNode *N,
 
 SDValue DAGTypeLegalizer::ScalarizeVecRes_BITCAST(SDNode *N) {
   SDValue Op = N->getOperand(0);
-  if (Op.getValueType().isVector()
-      && Op.getValueType().getVectorNumElements() == 1
-      && !isSimpleLegalType(Op.getValueType()))
+  if (getTypeAction(Op.getValueType()) == TargetLowering::TypeScalarizeVector)
     Op = GetScalarizedVector(Op);
   EVT NewVT = N->getValueType(0).getVectorElementType();
   return DAG.getNode(ISD::BITCAST, SDLoc(N),

topperc added a commit to topperc/llvm-project that referenced this issue Apr 15, 2025
@topperc
[LegalizeTypes] Check getTypeAction before calling GetScalarizedVector.
80d8029 
Use getTypeAction instead of trying to guess how a type will be
legalized. On AArch64, v1f16 is scalarized but v1f16 is widened.

Fixes llvm#135776
@topperc topperc mentioned this issue Apr 15, 2025
Merged
@EugeneZelenko EugeneZelenko added llvm:SelectionDAG SelectionDAGISel as well and removed backend:AArch64 labels Apr 15, 2025
var-const pushed a commit to ldionne/llvm-project that referenced this issue Apr 17, 2025
@topperc @var-const
[LegalizeTypes] Check getTypeAction before calling GetScalarizedVecto…

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O Apple Inc.
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Learn about vigilant mode
ddae1e7 
…r. (llvm#135838)

Use getTypeAction instead of trying to guess how a type will be
legalized. On AArch64, v1f16 is scalarized but v1f16 is widened.

Fixes llvm#135776
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[LegalizeTypes] Check getTypeAction before calling GetScalarizedVector. topperc/llvm-project
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