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<p class="MsoNormal"><span style="font-size:11.0pt;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";color:windowtext">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> Synth-diy [mailto:synth-diy-bounces@synth-diy.org]
<b>On Behalf Of </b>Steve via Synth-diy<br>
<br>
</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">>></span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">  You can force it to use registers by
 setting –O0 but then it doesn’t optimise the logic as you can’t switch optimisation levels inside functions.</span><o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-family:Wingdings;color:#1F497D"><span style="mso-list:Ignore">Ø<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]>I guess one could refactor something to have the bit that needs this trick as an inline function with a tagged __attribute__((optimize("O0"))) ?<br>
Never tried what happens there with inlines, whether the optimization level of the surrounding function overrides this... but just throwing this into GCC, it doesn't complain about this attribute being moot, like it tends to do when you do pointless stuff.<br>
<br>
<br>
<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">That doesn’t work I’m afraid.  It ignores it and swaps the register allocations, then in our case runs out of registers so uses a stack access.  I tore my hair
 out with the RP2040 toolset for several weeks trying to give it a try.  After almost a week of trial and error I eventually managed to get an AES (like SPDIF) receiver only one instruction more than Clang on gcc, but most other stuff was never in the ballpark,
 hence our use of cut, edit and pasting the assembly output from ARM compiler.  The sooner STM can supply proper MCUs again the better.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
<span style="color:#1F497D">> </span>I guess some people don't like being dependent on ever changing terms (read: the whims) of commercial tool vendors when avoidable.<span style="color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Never understood this myself.  We have to sell our products on performance and if a compiler gives us a competitive advantage we
 buy it, the same as we use a commercial PCB tool rather than Kicad.  And I’m not aware of any non-commercial EMI simulators, which tends to indicate to me that most people simply ignore EMI compliance.</span><br>
<br>
<o:p></o:p></p>
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