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<p class=MsoNormal>Hi all,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>It looks like LLVM is quite eager to load values into
registers when they have multiple uses. Unfortunately, this increases register
pressure, specifically on x86. In my experience modern x86 processors are very
capable of using memory operands as source. In fact the only cases where a
register is preferred over repeatedly using the same memory operand is when
multiple instructions could use the value in the same clock cycle, or when it
significantly reduces code size.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I have found this to be mostly a concern with SIMD code (MMX
and SSE). So if anyone could tell me where to find the code that determines
whether to load a value into a register or leave it in memory, I could perform
some tests to see if a better heuristic exists.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Nicolas Capens<o:p></o:p></p>
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