[Mesa-dev] [PATCH] gallivm: force sse instructions for llvm 3.5+

[Jose Fonseca]

On 02/10/14 03:09, Ilia Mirkin wrote:
> On Wed, Oct 1, 2014 at 10:56 AM, Maarten Lankhorst
> <maarten at mblankhorst.nl> wrote:
>> This fixes a crash when llvmpipe tries to use sse instructions,
>> but llvm detects a cpu that doesn't support them.
>>
>> Fixes for example piglit/bin/amd_seamless_cubemap_per_texture -fbo -auto
>> on i386 when run inside "qemu -cpu qemu32", which would otherwise error with:
>> "LLVM ERROR: Do not know how to split the result of this operator!"
>>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
>> ---
>>
>> diff --git a/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp b/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp
>> index 55aa8b9..f2f8906 100644
>> --- a/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp
>> +++ b/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp
>> @@ -479,10 +479,38 @@ lp_build_create_jit_compiler_for_module(LLVMExecutionEngineRef *OutJIT,
>>         if (util_cpu_caps.has_f16c) {
>>            MAttrs.push_back("+f16c");
>>         }
>> -      builder.setMAttrs(MAttrs);
>>      }
>>
>>   #if HAVE_LLVM >= 0x0305
>> +   /*
>> +    * llvm 3.5 no longer supports cpuid based autodetect.
>> +    * This breaks on "qemu -cpu qemu32" which is detected as pentium2 by llvm's
>> +    * sys::getHostCPUName(), but does support sse2.
>> +    *
>> +    * For this reason force the use of sse extensions when available, so our
>> +    * understanding of the cpu is in sync with llvm's.
>> +    */
>> +
>> +   else if (util_cpu_caps.has_sse4_2)
>> +      MAttrs.push_back("+sse42");
>> +   else if (util_cpu_caps.has_sse4_1)
>> +      MAttrs.push_back("+sse41");
>> +   else if (util_cpu_caps.has_ssse3)
>> +      MAttrs.push_back("+ssse3");
>> +   else if (util_cpu_caps.has_sse3)
>> +      MAttrs.push_back("+sse3");
>> +   else if (util_cpu_caps.has_sse2)
>> +      MAttrs.push_back("+sse2");
>> +   else if (util_cpu_caps.has_sse)
>> +      MAttrs.push_back("+sse");
>> +   else if (util_cpu_caps.has_mmx)
>> +      MAttrs.push_back("+sse");
>
> I'm not familiar with LLVM, but if this isn't a typo (i.e. "+mmx"),
> this probably deserves a comment. Also does +sse42 imply all the other
> "lower" SSE instructions?

Actually, I think it's better not to enable MMX, 3DNow, or anything that 
operates on XMM registers, as mixing code that operates on SSE and MMX 
registers is complicated and inefficient.

Jose