[llvm-dev] Help: Implementing function call lowering for a Backend

Sat Apr 11 05:01:25 PDT 2020

Hi everyone,

I am currently working on a backend for my bachelor thesis, using the
patches by alex bradbury as a reference (
https://github.com/lowRISC/riscv-llvm).

However, whenever I try to lower the following file:

play/call.ll:
> declare i32 @external_function(i64)

> define i32 @test_call_external(i64 %a) nounwind {
>   %1 = add i64 %a, %a
>   %2 = call i32 @external_function(i64 %1)
>   ret i32 %2
> }

with
$ ./bin/llc -mtriple=via64 play/call.ll

TargetRegisterInfo::getMinimalPhysRegClass() fails because it could find an
appropriate Register Class.
I put a copy of the stack dump at the bottom.

The register i am passing should be i64 (i checked at runtime, and it is).
And my defined registers are all 64 bit as well.

Does anyone know what could be wrong?
I understand that this is probably not enough information to answer my
question, but I didn't exactly know what code to send.

Cheers,
Floris Westermann

Stack dump:

> $ ./bin/llc -mtriple=via64 play/call.ll
>
> llc: ../lib/CodeGen/TargetRegisterInfo.cpp:208: const
llvm::TargetRegisterClass
*llvm::TargetRegisterInfo::getMinimalPhysRegClass(unsigned int, llvm::MVT)
const: Assertion `BestRC && "Couldn't find the register class"' failed.
> Stack dump:
> 0. Program arguments: ./bin/llc -mtriple=via64 play/call.ll
> 1. Running pass 'Function Pass Manager' on module 'play/call.ll'.
> 2. Running pass 'VIA64 DAG->DAG Pattern Instruction Selection' on
function '@test_call_external'
>  #0 0x00007f5dfb508709 llvm::sys::PrintStackTrace(llvm::raw_ostream&)
/home/fooris/github/llvm/build/../lib/Support/Unix/Signals.inc:544:11
>  #1 0x00007f5dfb5088b9 PrintStackTraceSignalHandler(void*)
/home/fooris/github/llvm/build/../lib/Support/Unix/Signals.inc:605:1
>  #2 0x00007f5dfb5070b6 llvm::sys::RunSignalHandlers()
/home/fooris/github/llvm/build/../lib/Support/Signals.cpp:67:5
>  #3 0x00007f5dfb50904d SignalHandler(int)
/home/fooris/github/llvm/build/../lib/Support/Unix/Signals.inc:391:1
>  #4 0x00007f5dfa275890 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
>  #5 0x00007f5df9571e97 raise
/build/glibc-OTsEL5/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
>  #6 0x00007f5df9573801 abort
/build/glibc-OTsEL5/glibc-2.27/stdlib/abort.c:81:0
>  #7 0x00007f5df956339a __assert_fail_base
/build/glibc-OTsEL5/glibc-2.27/assert/assert.c:89:0
>  #8 0x00007f5df9563412 (/lib/x86_64-linux-gnu/libc.so.6+0x30412)
>  #9 0x00007f5dfe84376a
llvm::TargetRegisterInfo::getMinimalPhysRegClass(unsigned int, llvm::MVT)
const
/home/fooris/github/llvm/build/../lib/CodeGen/TargetRegisterInfo.cpp:209:10
> #10 0x00007f5dfbace437 CheckForPhysRegDependency(llvm::SDNode*,
llvm::SDNode*, unsigned int, llvm::TargetRegisterInfo const*,
llvm::TargetInstrInfo const*, unsigned int&, int&)
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp:133:32
> #11 0x00007f5dfbacdfeb llvm::ScheduleDAGSDNodes::AddSchedEdges()
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp:487:9
> #12 0x00007f5dfbace492
llvm::ScheduleDAGSDNodes::BuildSchedGraph(llvm::AAResults*)
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp:538:1
> #13 0x00007f5dfbab9d05 (anonymous
namespace)::ScheduleDAGRRList::Schedule()
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp:0:3
> #14 0x00007f5dfbacbcfd llvm::ScheduleDAGSDNodes::Run(llvm::SelectionDAG*,
llvm::MachineBasicBlock*)
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp:64:1
> #15 0x00007f5dfbbe0d70 llvm::SelectionDAGISel::CodeGenAndEmitDAG()
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:986:16
> #16 0x00007f5dfbbdf3e0
llvm::SelectionDAGISel::SelectBasicBlock(llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction,
true, false, void>, false, true>,
llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction,
true, false, void>, false, true>, bool&)
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:735:1
> #17 0x00007f5dfbbdeecd
llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&)
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:0:7
> #18 0x00007f5dfbbdc278
llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&)
/home/fooris/github/llvm/build/../lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:502:22
> #19 0x00007f5dfe50b4a2
llvm::MachineFunctionPass::runOnFunction(llvm::Function&)
/home/fooris/github/llvm/build/../lib/CodeGen/MachineFunctionPass.cpp:73:8
> #20 0x00007f5dfd9998ac
llvm::FPPassManager::runOnFunction(llvm::Function&)
/home/fooris/github/llvm/build/../lib/IR/LegacyPassManager.cpp:1648:23
> #21 0x00007f5dfd999cc5 llvm::FPPassManager::runOnModule(llvm::Module&)
/home/fooris/github/llvm/build/../lib/IR/LegacyPassManager.cpp:1684:16
> #22 0x00007f5dfd99a444 (anonymous
namespace)::MPPassManager::runOnModule(llvm::Module&)
/home/fooris/github/llvm/build/../lib/IR/LegacyPassManager.cpp:1749:23
> #23 0x00007f5dfd999f58 llvm::legacy::PassManagerImpl::run(llvm::Module&)
/home/fooris/github/llvm/build/../lib/IR/LegacyPassManager.cpp:1862:16
> #24 0x00007f5dfd99a9d1 llvm::legacy::PassManager::run(llvm::Module&)
/home/fooris/github/llvm/build/../lib/IR/LegacyPassManager.cpp:1893:3
> #25 0x000000000041fb11 compileModule(char**, llvm::LLVMContext&)
/home/fooris/github/llvm/build/../tools/llc/llc.cpp:605:41
> #26 0x000000000041e19d main
/home/fooris/github/llvm/build/../tools/llc/llc.cpp:355:13
> #27 0x00007f5df9554b97 __libc_start_main
/build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
> #28 0x000000000041d8da _start (./bin/llc+0x41d8da)
> [1]    24145 abort      ./bin/llc -mtriple=via64 play/call.ll
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