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<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">It should not read global memory again. We already enable such kind of optimization pass in LLVM.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">And (a*b+c*d) should not calculate again. This is common-subexpression. Clang should do it easily. But I am not quite sure whether clang is affected
by -O2 or -O0. Anyone know details?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D">To check specific kernel. You may need to ¡®export OCL_OUTPUT_LLVM_AFTER_GEN=1¡¯ and build your program again to get the LLVM IR.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Beignet [mailto:beignet-bounces@lists.freedesktop.org]
<b>On Behalf Of </b></span><span style="font-size:10.0pt">Åíϯºº</span><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""><br>
<b>Sent:</b> Thursday, February 12, 2015 4:40 PM<br>
<b>To:</b> beignet@lists.freedesktop.org<br>
<b>Subject:</b> [Beignet] a question about default optimize option when building<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Hi:<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">My CL kernel program looks like as follow:<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">__global unsigned char *p;<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">int a, b, c, d;<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">res1 = *p * (a*b + c*d);<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><some code here><o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">res2 = *p * (a*b + c*d + 1);<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"> <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">If I use default build option, for res2, what will EU do? read global memory for pointer p again and do computing of "a*b + c*d" again? <o:p></o:p></span></p>
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