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R600 Gallium3D Disables LLVM Back-End By Default

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  • R600 Gallium3D Disables LLVM Back-End By Default

    Phoronix: R600 Gallium3D Disables LLVM Back-End By Default

    AMD has decided to disable the LLVM compiler back-end by default within the R600 era Gallium3D graphics driver...

    http://www.phoronix.com/vr.php?view=MTY2NjI

  • #2
    Does this means less performance? And are we talking about mesa 10.2?, because its not explained.
    Last edited by edoantonioco; 04-16-2014, 10:57 PM.

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    • #3
      Originally posted by edoantonioco View Post
      Does this means less performance? And are we talking about mesa 10.2?, because its not explained.
      It means worse performance, but better compatibility. And yes, we're talking about Mesa 10.2. Any change to Mesa that isn't a bug fix is assumed to be for the next version.

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      • #4
        Originally posted by Plombo View Post
        It means worse performance, but better compatibility. And yes, we're talking about Mesa 10.2. Any change to Mesa that isn't a bug fix is assumed to be for the next version.
        Are you sure there's a performance hit ? My recollection was that Vadim's "sb" option was running at about the same speed as llvm, and I believe it was enabled by default.

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        • #5
          Originally posted by bridgman View Post
          Are you sure there's a performance hit ? My recollection was that Vadim's "sb" option was running at about the same speed as llvm, and I believe it was enabled by default.
          Ah, you're probably right. I had forgotten about Vadim's compiler.

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          • #6
            On my previous a10-5800k APU, Vadim's SB compiler was much better than llvm. I tested it a lot.

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            • #7
              Originally posted by edoantonioco View Post
              Does this means less performance?
              That depends on the hardware I guess. On my card (HD 6950) LLVM causes more stuttering.

              Originally posted by bridgman View Post
              My recollection was that Vadim's "sb" option was running at about the same speed as llvm, and I believe it was enabled by default.
              But Vadim's "sb" option can be enabled with LLVM, too. IIRC it's a shader optimization that happens after the shader has been compiled.

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              • #8
                Does this also mean that r600 will never get FOSS OpenCL ?? (when and if ready)

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                • #9
                  " --enable-r600-llvm-compiler [...] but now not even that will disable the compiler back-end by default for this driver." IMHO it should say enable not disable otherwise I fail to find logical conclusion from that statement.

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                  • #10
                    Originally posted by 89c51 View Post
                    Does this also mean that r600 will never get FOSS OpenCL ?? (when and if ready)
                    No, it just disables the LLVM backend for the shader compiler. OpenCL is a different thing.

                    Originally posted by ryszardzonk View Post
                    " --enable-r600-llvm-compiler [...] but now not even that will disable the compiler back-end by default for this driver." IMHO it should say enable not disable otherwise I fail to find logical conclusion from that statement.
                    The statement is correct. If you compile mesa without --enable-r600-llvm-compiler you can't enable it at all. If you compile with --enable-r600-llvm-compiler it is still disabled by default but you're able to enable it with R600_DEBUG=llvm

                    //EDIT: In other words: --enable-r600-llvm-compiler compiles the support in (this is a compile-time switch) while R600_DEBUG=llvm enables it at runtime (it is a runtime switch).
                    Last edited by V10lator; 04-17-2014, 07:18 AM.

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