[flang] Improper casting of integer(2) selector for computed gotos

[VijayKandiah]

Reproducer:

program test
    implicit none
    integer(2) :: ix
    
    ix = 1
    goto(10) ix
  10 continue
    print *, 'success'
    
end program test

$ flang test.f90 
flang: llvm-project/llvm/lib/IR/Instructions.cpp:3041: static CastInst *llvm::CastInst::Create(Instruction::CastOps, Value *, Type *, const Twine &, InsertPosition): Assertion `castIsValid(op, S, Ty) && "Invalid cast!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.

Changing the selector ix's type to integer(4) works but using type integer(2) does not.

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Vijay Kandiah (VijayKandiah)

Reproducer:

program test
    implicit none
    integer(2) :: ix
    
    ix = 1
    goto(10) ix
  10 continue
    print *, 'success'
    
end program test

$ flang test.f90 
flang: llvm-project/llvm/lib/IR/Instructions.cpp:3041: static CastInst *llvm::CastInst::Create(Instruction::CastOps, Value *, Type *, const Twine &, InsertPosition): Assertion `castIsValid(op, S, Ty) && "Invalid cast!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.

Changing the selector ix's type to integer(4) works but using type integer(2) does not.

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: Vijay Kandiah (VijayKandiah)

Reproducer:

program test
    implicit none
    integer(2) :: ix
    
    ix = 1
    goto(10) ix
  10 continue
    print *, 'success'
    
end program test

$ flang test.f90 
flang: llvm-project/llvm/lib/IR/Instructions.cpp:3041: static CastInst *llvm::CastInst::Create(Instruction::CastOps, Value *, Type *, const Twine &, InsertPosition): Assertion `castIsValid(op, S, Ty) && "Invalid cast!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.

Changing the selector ix's type to integer(4) works but using type integer(2) does not.

[eugeneepshteyn]

I suspect the issue is in lowering. Perhaps creation of SelectOp assumes i32 type for some values, instead of getting i16 type from the value.

[vzakhari]

I think the issue is in CodeGen. fir.select allows any integer operand for the selector, and CodeGen fails to cast it to I32 properly.