[Mesa-dev] [PATCH v3 12/25] configure.ac: Move gallium LLVM checks

[Jose Fonseca]

On 12/10/16 19:30, Emil Velikov wrote:
> On 12 October 2016 at 19:14, Tobias Droste <tdroste at gmx.de> wrote:
>> Am Mittwoch, 12. Oktober 2016, 10:42:19 CEST schrieb Emil Velikov:
>>> On 12 October 2016 at 00:02, Tobias Droste <tdroste at gmx.de> wrote:
>>>>
>>>>  gallium_require_llvm() {
>>>>
>>>> -    if test "x$MESA_LLVM" = x0; then
>>>> -        case "$host" in *gnux32) return;; esac
>>>> -        case "$host_cpu" in
>>>> -        i*86|x86_64|amd64) AC_MSG_ERROR([LLVM is required to build $1 on
>>>> x86 and x86_64]);; -        esac
>>>> -    fi
>>>> +    case "$host" in *gnux32) return;; esac
>>>> +    case "$host_cpu" in
>>>> +    i*86|x86_64|amd64)
>>>> +        LLVM_REQUIRED_VERSION_MAJOR="3"
>>>> +        LLVM_REQUIRED_VERSION_MINOR="3"
>>>> +        if test "$LLVM_VERSION_INT" -lt
>>>> "${LLVM_REQUIRED_VERSION_MAJOR}0${LLVM_REQUIRED_VERSION_MINOR}"; then +
>>>>          AC_MSG_ERROR([LLVM
>>>> $LLVM_REQUIRED_VERSION_MAJOR.$LLVM_REQUIRED_VERSION_MINOR or newer is
>>>> required]) +        fi
>>>> +        ;;
>>>> +    esac
>>>>
>>>>  }
>>>
>>> The function it quite "ugly" as-is and this patch changes things in a fun
>>> way.
>>>
>>> Namely: before you'll get the minimum required version check
>>> regardless of host_cpu for everyone, while now you get the opposite -
>>> everyone is 'constrained' by the host_cpu check. Admittedly I've have
>>> not idea if llvmpipe is a thing on outside x86 land.
>>>
>>> Checking the gallium_require_llvm users we want:
>>>  - swr -> bail out if host_cpu !x86/x86-64 or gallium-llvm toggle is
>>> off || llvm version req. is not met
>>>  - r300 -> on host_cpu eq. x86/x86-64, check the gallium-llvm toggle
>>> (this is 'premature' optimisation which we might want to rework/drop
>>> in the long run)
>>
>> Right now --enable-gallium-llvm will be set to no if it is "auto" on non x86.
>
>> gallivm/llvm use the x86 target
> I haven't look too closely at the llvm code but there's nothing in
> scons/automake which supports this, perhaps Jose can confirm.
>
> Jose, does the gallium llvm code require the x86 target or can it work
> with other as well ? At least in theory.

At VMware we only use llvmpipe + LLVM with x86: we have CI in place to 
make sure it works.

I understand others have it working with PowerPC and ARM.  The code is 
there.  So we shouln't forbid people from enabling if they want.

(In fact, in theory llvmpipe should work any CPU that's supported by 
LLVM.  But I wouldn't be surprised if there are bugs in practice.)


I'm not involved in these porting efforts myself.  I don't know how 
stable llvmpipe on PowerPC/ARM is kept (whether there's any CI in 
place), and therefore I can't say it's OK to enable LLVM by default 
outside x86 or not.


Jose