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Urgau opened this issue May 10, 2025 · 1 comment · Fixed by #142170
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[aarch64] Cannot select: constant:i128<0> for llvm.maximum.f128 #139380

Urgau opened this issue May 10, 2025 · 1 comment · Fixed by #142170
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@nikic
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backend:AArch64 crash Prefer [crash-on-valid] or [crash-on-invalid] llvm:SelectionDAG SelectionDAGISel as well

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@Urgau
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Urgau commented May 10, 2025

I'm seeing an error when trying to use llvm.minimum.f128 and llvm.maximum.f128 on aarch64.

define fp128 @call_maximum_fp128(fp128 %x, fp128 %y) unnamed_addr #0 {
start:
  %0 = tail call fp128 @llvm.maximum.f128(fp128 %x, fp128 %y) #2
  ret fp128 %0
}

; Function Attrs: mustprogress nofree nosync nounwind readnone speculatable willreturn
declare fp128 @llvm.maximum.f128(fp128, fp128)
LLVM ERROR: Cannot select: 0x10c8bea0: i32 = setcc 0x10c888c0, Constant:i128<0>, seteq:ch
  0x10c888c0: i128 = bitcast 0x10c87fd8
    0x10c87fd8: f128,ch = CopyFromReg 0x10c105c0, Register:f128 %1
      0x10c87f60: f128 = Register %1
  0x10c8bbd0: i128 = Constant<0>
In function: call_maximum_fp128
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-trunk/bin/llc -o /app/output.s -x86-asm-syntax=intel <source>
1.	Running pass 'Function Pass Manager' on module '<source>'.
2.	Running pass 'AArch64 Instruction Selection' on function '@call_maximum_fp128'
 #0 0x0000000003b49548 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-trunk/bin/llc+0x3b49548)
 #1 0x0000000003b47104 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #2 0x000073d283c42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #3 0x000073d283c969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #4 0x000073d283c42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #5 0x000073d283c287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #6 0x0000000000784592 llvm::UniqueStringSaver::save(llvm::Twine const&) (.cold) StringSaver.cpp:0:0
 #7 0x00000000038f0888 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) (/opt/compiler-explorer/clang-trunk/bin/llc+0x38f0888)
 #8 0x00000000038f6bf9 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/opt/compiler-explorer/clang-trunk/bin/llc+0x38f6bf9)
 #9 0x0000000000bfa944 (anonymous namespace)::AArch64DAGToDAGISel::Select(llvm::SDNode*) AArch64ISelDAGToDAG.cpp:0:0
#10 0x00000000038edd74 llvm::SelectionDAGISel::DoInstructionSelection() (/opt/compiler-explorer/clang-trunk/bin/llc+0x38edd74)
#11 0x00000000038fc882 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/opt/compiler-explorer/clang-trunk/bin/llc+0x38fc882)
#12 0x00000000038ff1fa llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/opt/compiler-explorer/clang-trunk/bin/llc+0x38ff1fa)
#13 0x00000000039010d6 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-trunk/bin/llc+0x39010d6)
#14 0x00000000038ed8f1 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-trunk/bin/llc+0x38ed8f1)
#15 0x0000000002bb4a78 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#16 0x0000000003135322 llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-trunk/bin/llc+0x3135322)
#17 0x00000000031355b1 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-trunk/bin/llc+0x31355b1)
#18 0x0000000003136f19 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-trunk/bin/llc+0x3136f19)
#19 0x00000000008bec3f compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#20 0x000000000079977e main (/opt/compiler-explorer/clang-trunk/bin/llc+0x79977e)
#21 0x000073d283c29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#22 0x000073d283c29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#23 0x00000000008b6705 _start (/opt/compiler-explorer/clang-trunk/bin/llc+0x8b6705)
Program terminated with signal: SIGSEGV
Compiler returned: 139

https://godbolt.org/z/YWdK1ecM5
@Urgau Urgau mentioned this issue May 10, 2025
Merged
@frederick-vs-ja frederick-vs-ja added backend:AArch64 crash Prefer [crash-on-valid] or [crash-on-invalid] llvm:SelectionDAG SelectionDAGISel as well and removed new issue labels May 10, 2025
@llvmbot
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llvmbot commented May 10, 2025

@llvm/issue-subscribers-backend-aarch64

Author: None (Urgau)

I'm seeing an error when trying to use `llvm.minimum.f128` and `llvm.maximum.f128` on aarch64. 
define fp128 @<!-- -->call_maximum_fp128(fp128 %x, fp128 %y) unnamed_addr #<!-- -->0 {
start:
  %0 = tail call fp128 @<!-- -->llvm.maximum.f128(fp128 %x, fp128 %y) #<!-- -->2
  ret fp128 %0
}

; Function Attrs: mustprogress nofree nosync nounwind readnone speculatable willreturn
declare fp128 @<!-- -->llvm.maximum.f128(fp128, fp128)
LLVM ERROR: Cannot select: 0x10c8bea0: i32 = setcc 0x10c888c0, Constant:i128&lt;0&gt;, seteq:ch
  0x10c888c0: i128 = bitcast 0x10c87fd8
    0x10c87fd8: f128,ch = CopyFromReg 0x10c105c0, Register:f128 %1
      0x10c87f60: f128 = Register %1
  0x10c8bbd0: i128 = Constant&lt;0&gt;
In function: call_maximum_fp128
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-trunk/bin/llc -o /app/output.s -x86-asm-syntax=intel &lt;source&gt;
1.	Running pass 'Function Pass Manager' on module '&lt;source&gt;'.
2.	Running pass 'AArch64 Instruction Selection' on function '@<!-- -->call_maximum_fp128'
 #<!-- -->0 0x0000000003b49548 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/compiler-explorer/clang-trunk/bin/llc+0x3b49548)
 #<!-- -->1 0x0000000003b47104 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #<!-- -->2 0x000073d283c42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #<!-- -->3 0x000073d283c969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #<!-- -->4 0x000073d283c42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #<!-- -->5 0x000073d283c287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #<!-- -->6 0x0000000000784592 llvm::UniqueStringSaver::save(llvm::Twine const&amp;) (.cold) StringSaver.cpp:0:0
 #<!-- -->7 0x00000000038f0888 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) (/opt/compiler-explorer/clang-trunk/bin/llc+0x38f0888)
 #<!-- -->8 0x00000000038f6bf9 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/opt/compiler-explorer/clang-trunk/bin/llc+0x38f6bf9)
 #<!-- -->9 0x0000000000bfa944 (anonymous namespace)::AArch64DAGToDAGISel::Select(llvm::SDNode*) AArch64ISelDAGToDAG.cpp:0:0
#<!-- -->10 0x00000000038edd74 llvm::SelectionDAGISel::DoInstructionSelection() (/opt/compiler-explorer/clang-trunk/bin/llc+0x38edd74)
#<!-- -->11 0x00000000038fc882 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/opt/compiler-explorer/clang-trunk/bin/llc+0x38fc882)
#<!-- -->12 0x00000000038ff1fa llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&amp;) (/opt/compiler-explorer/clang-trunk/bin/llc+0x38ff1fa)
#<!-- -->13 0x00000000039010d6 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/compiler-explorer/clang-trunk/bin/llc+0x39010d6)
#<!-- -->14 0x00000000038ed8f1 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/compiler-explorer/clang-trunk/bin/llc+0x38ed8f1)
#<!-- -->15 0x0000000002bb4a78 llvm::MachineFunctionPass::runOnFunction(llvm::Function&amp;) (.part.0) MachineFunctionPass.cpp:0:0
#<!-- -->16 0x0000000003135322 llvm::FPPassManager::runOnFunction(llvm::Function&amp;) (/opt/compiler-explorer/clang-trunk/bin/llc+0x3135322)
#<!-- -->17 0x00000000031355b1 llvm::FPPassManager::runOnModule(llvm::Module&amp;) (/opt/compiler-explorer/clang-trunk/bin/llc+0x31355b1)
#<!-- -->18 0x0000000003136f19 llvm::legacy::PassManagerImpl::run(llvm::Module&amp;) (/opt/compiler-explorer/clang-trunk/bin/llc+0x3136f19)
#<!-- -->19 0x00000000008bec3f compileModule(char**, llvm::LLVMContext&amp;) llc.cpp:0:0
#<!-- -->20 0x000000000079977e main (/opt/compiler-explorer/clang-trunk/bin/llc+0x79977e)
#<!-- -->21 0x000073d283c29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#<!-- -->22 0x000073d283c29e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#<!-- -->23 0x00000000008b6705 _start (/opt/compiler-explorer/clang-trunk/bin/llc+0x8b6705)
Program terminated with signal: SIGSEGV
Compiler returned: 139

https://godbolt.org/z/YWdK1ecM5

This was referenced May 14, 2025
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Open
@nikic nikic self-assigned this May 30, 2025
@nikic nikic mentioned this issue Jun 2, 2025
Merged
nikic added a commit that referenced this issue Jun 2, 2025
@nikic
[SDAG] Fix fmaximum legalization errors (#142170)
58cc167 
FMAXIMUM is currently legalized via IS_FPCLASS for the signed zero
handling. This is problematic, because it assumes the equivalent integer
type is legal. Many targets have legal fp128, but illegal i128, so this
results in legalization failures.

Fix this by replacing IS_FPCLASS with checking the bitcast to integer
instead. In that case it is sufficient to use any legal integer type, as
we're just interested in the sign bit. This can be obtained via a stack
temporary cast. There is existing FloatSignAsInt functionality used for
legalization of FABS and similar we can use for this purpose.

Fixes #139380.
Fixes #139381.
Fixes #140445.
llvm-sync bot pushed a commit to arm/arm-toolchain that referenced this issue Jun 2, 2025
@nikic @github-actions
Automerge: [SDAG] Fix fmaximum legalization errors (#142170)
1c7a1a1 
FMAXIMUM is currently legalized via IS_FPCLASS for the signed zero
handling. This is problematic, because it assumes the equivalent integer
type is legal. Many targets have legal fp128, but illegal i128, so this
results in legalization failures.

Fix this by replacing IS_FPCLASS with checking the bitcast to integer
instead. In that case it is sufficient to use any legal integer type, as
we're just interested in the sign bit. This can be obtained via a stack
temporary cast. There is existing FloatSignAsInt functionality used for
legalization of FABS and similar we can use for this purpose.

Fixes llvm/llvm-project#139380.
Fixes llvm/llvm-project#139381.
Fixes llvm/llvm-project#140445.
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[SDAG] Fix fmaximum legalization errors nikic/llvm-project
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