This section contains significant known problems with the LLVM system, listed - by component. If you run into a problem, please check - the LLVM bug database and submit a bug if - there isn't already one.

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- Experimental features included with this release -

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The following components of this LLVM release are either untested, known to - be broken or unreliable, or are in early development. These components - should not be relied on, and bugs should not be filed against them, but they - may be useful to some people. In particular, if you would like to work on - one of these components, please contact us on - the LLVMdev - list.

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The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ and - XCore backends are experimental.
llc "-filetype=obj" is experimental on all targets other - than darwin and ELF X86 systems.

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- Known problems with the X86 back-end -

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The X86-64 backend does not yet support - the va_arg LLVM IR instruction. Currently, front-ends support - variadic argument constructs on X86-64 by lowering them manually.

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- Known problems with the PowerPC back-end -

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The PPC32/ELF support lacks PIC support.

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- Known problems with the ARM back-end -

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Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6 - processors, thumb programs can crash or produce wrong results - (PR1388).
Compilation for ARM Linux OABI (old ABI) is supported but not fully - tested.

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- Known problems with the SPARC back-end -

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The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not - support the 64-bit SPARC ABI (-m64).

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- Known problems with the MIPS back-end -

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64-bit MIPS targets are not supported yet.

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- Known problems with the Alpha back-end -

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On 21164s, some rare FP arithmetic sequences which may trap do not have - the appropriate nops inserted to ensure restartability.

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- Known problems with the C back-end -

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The C backend has numerous problems and is not being actively maintained. - Depending on it for anything serious is not advised.

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LLVM is generally a production quality compiler, and is used by a broad range + of applications and shipping in many products. That said, not every + subsystem is as mature as the aggregate, particularly the more obscure + targets. If you run into a problem, please check the LLVM bug database and submit a bug if + there isn't already one or ask on the LLVMdev + list.

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Known problem areas include:

The C backend has only basic support for - inline assembly code.
The C backend violates the ABI of common - C++ programs, preventing intermixing between C++ compiled by the CBE - and C++ code compiled with llc or native compilers.
The C backend does not support all exception handling constructs.
The C backend does not support arbitrary precision integers.
The Alpha, Blackfin, CellSPU, MSP430, PTX, SystemZ and + XCore backends are experimental, and several of these have already been + removed from mainline.
The integrated assembler, disassembler, and JIT is not supported by + several targets. If an integrated assembler is not supported, then a + system assembler is required. For more details, see the Target Features Matrix. +
The C backend has numerous problems and is not being actively maintained. + Depending on it for anything serious is not advised.