Compiler may fail with "Bad kind" diagnostic when using --neon and unaligned data

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    • Type: Bug
    • Resolution: Fixed
    • Priority: Medium
    • Code Generation Tools
    • CODEGEN-7623
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      ARM_18.12.0.LTS
      ARM_20.2.0.LTS
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      ARM_18.12.0.LTS ARM_20.2.0.LTS
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      ARM_18.12.7.LTS*
      ARM_20.2.2.LTS*
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      ARM_18.12.7.LTS* ARM_20.2.2.LTS*
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      Add "#pragma UNROLL(1)" (up to UNROLL(4), but definitely not UNROLL(8)) to the for-loop in ComputeChecksum().

      Or, compile at -o1 or less, or don't use --neon.
      Show
      Add "#pragma UNROLL(1)" (up to UNROLL(4), but definitely not UNROLL(8)) to the for-loop in ComputeChecksum(). Or, compile at -o1 or less, or don't use --neon.
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      When compiling with '-mv7a8 --neon' and optimisation, the compiler will try to vectorise data accesses to take advantage of the Neon capabilities. If it creates an unaligned access of more than 32 bits, the compiler may abort with the one-line diagnostic "TP>> internal error: Bad kind: TYPE::elem_type()".

      In this particular test case, the compiler is making a 64-bit vector from chars that start at an offset in a struct, by unrolling a loop that operates on chars. The solution is to avoid making vectors more than 32 bits, by controlling the unroll amount, via the UNROLL pragma or the optimisation level.
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      When compiling with '-mv7a8 --neon' and optimisation, the compiler will try to vectorise data accesses to take advantage of the Neon capabilities. If it creates an unaligned access of more than 32 bits, the compiler may abort with the one-line diagnostic "TP>> internal error: Bad kind: TYPE::elem_type()". In this particular test case, the compiler is making a 64-bit vector from chars that start at an offset in a struct, by unrolling a loop that operates on chars. The solution is to avoid making vectors more than 32 bits, by controlling the unroll amount, via the UNROLL pragma or the optimisation level.

      Use the attached files ...

      % armcl -@options.txt --diag_suppress=179 try1.cpp
TP>> internal error: Bad kind:  TYPE::elem_type()

>> Compilation failure

      One workaround is to use --opt_level=2 or lower.

      The forum customer originally reported the problem against version 17.9.0.STS. That version fails with a different diagnostic.

      % armcl -@options.txt --diag_suppress=179 try1.cpp
>> try1.cpp, line 53340: INTERNAL ERROR: no match for SCONV


This may be a serious problem.  Please contact customer support with a
description of this problem and a sample of the source files that caused this
INTERNAL ERROR message to appear.

Cannot continue compilation - ABORTING!


>> Compilation failure

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            TI User
            Reporter:
            TI User
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                Connection: Intermediate to External PROD System
                EXTSYNC-2337 - Compiler may fail with "Bad kind" d...
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