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

[Ilia Mirkin]

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?

> +
> +   if (util_cpu_caps.has_3dnow_ext)
> +      MAttrs.push_back("+3dnowa");
> +   else if (util_cpu_caps.has_3dnow)
> +      MAttrs.push_back("+3dnow");
> +
>     StringRef MCPU = llvm::sys::getHostCPUName();
>     /*
>      * The cpu bits are no longer set automatically, so need to set mcpu manually.
> @@ -498,6 +526,7 @@ lp_build_create_jit_compiler_for_module(LLVMExecutionEngineRef *OutJIT,
>      */
>     builder.setMCPU(MCPU);
>  #endif
> +   builder.setMAttrs(MAttrs);
>
>     ShaderMemoryManager *MM = new ShaderMemoryManager();
>     *OutCode = MM->getGeneratedCode();
>
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