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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas">// Test case:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas">typedef struct { int a; int b; int c; int d; int e; int f; } T;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas">extern int foo(T a);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas">extern T blah;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas">int boo() {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas"> return foo(blah);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt;font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas">// Generated code (Clang -O3) – trunk, 10.0.0 (</span><a href="https://godbolt.org/">https://godbolt.org/</a><span style="font-size:12.0pt;font-family:Consolas">):<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:teal">boo:</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:green"># @boo</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">subq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:#3030C0">$56</span><span style="font-family:"Consolas,",serif;color:black">, </span><span style="font-family:"Consolas,",serif;color:#4864AA">%rsp</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">movq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:teal">blah</span><span style="font-family:"Consolas,",serif;color:black">+</span><span style="font-family:"Consolas,",serif;color:#098658">16</span><span style="font-family:"Consolas,",serif;color:black">(</span><span style="font-family:"Consolas,",serif;color:#4864AA">%rip</span><span style="font-family:"Consolas,",serif;color:black">), </span><span style="font-family:"Consolas,",serif;color:#4864AA">%rax</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue;background:yellow;mso-highlight:yellow">movq</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow"> </span><span style="font-family:"Consolas,",serif;color:#4864AA;background:yellow;mso-highlight:yellow">%rax</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">, </span><span style="font-family:"Consolas,",serif;color:#098658;background:yellow;mso-highlight:yellow">48</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">(</span><span style="font-family:"Consolas,",serif;color:#4864AA;background:yellow;mso-highlight:yellow">%rsp</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">)</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">movups</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:teal">blah</span><span style="font-family:"Consolas,",serif;color:black">(</span><span style="font-family:"Consolas,",serif;color:#4864AA">%rip</span><span style="font-family:"Consolas,",serif;color:black">), </span><span style="font-family:"Consolas,",serif;color:#4864AA">%xmm0</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue;background:yellow;mso-highlight:yellow">movaps</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow"> </span><span style="font-family:"Consolas,",serif;color:#4864AA;background:yellow;mso-highlight:yellow">%xmm0</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">, </span><span style="font-family:"Consolas,",serif;color:#098658;background:yellow;mso-highlight:yellow">32</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">(</span><span style="font-family:"Consolas,",serif;color:#4864AA;background:yellow;mso-highlight:yellow">%rsp</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">)</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue;background:yellow;mso-highlight:yellow">movq</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow"> </span><span style="font-family:"Consolas,",serif;color:#098658;background:yellow;mso-highlight:yellow">48</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">(</span><span style="font-family:"Consolas,",serif;color:#4864AA;background:yellow;mso-highlight:yellow">%rsp</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">), </span><span style="font-family:"Consolas,",serif;color:#4864AA;background:yellow;mso-highlight:yellow">%rax</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">movq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:#4864AA">%rax</span><span style="font-family:"Consolas,",serif;color:black">, </span><span style="font-family:"Consolas,",serif;color:#098658">16</span><span style="font-family:"Consolas,",serif;color:black">(</span><span style="font-family:"Consolas,",serif;color:#4864AA">%rsp</span><span style="font-family:"Consolas,",serif;color:black">)<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue;background:yellow;mso-highlight:yellow">movaps</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow"> </span><span style="font-family:"Consolas,",serif;color:#098658;background:yellow;mso-highlight:yellow">32</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">(</span><span style="font-family:"Consolas,",serif;color:#4864AA;background:yellow;mso-highlight:yellow">%rsp</span><span style="font-family:"Consolas,",serif;color:black;background:yellow;mso-highlight:yellow">), </span><span style="font-family:"Consolas,",serif;color:#4864AA;background:yellow;mso-highlight:yellow">%xmm0</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">movups</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:#4864AA">%xmm0</span><span style="font-family:"Consolas,",serif;color:black">, (</span><span style="font-family:"Consolas,",serif;color:#4864AA">%rsp</span><span style="font-family:"Consolas,",serif;color:black">)<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">callq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:teal">foo</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">addq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:#3030C0">$56</span><span style="font-family:"Consolas,",serif;color:black">, </span><span style="font-family:"Consolas,",serif;color:#4864AA">%rsp</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">retq<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas">// Generated code (gcc -O3) – 7.3.0 (</span><a href="https://godbolt.org/">https://godbolt.org/</a><span style="font-size:12.0pt;font-family:Consolas">):<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:teal">boo:</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">subq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:#3030C0">$40</span><span style="font-family:"Consolas,",serif;color:black">, </span><span style="font-family:"Consolas,",serif;color:#4864AA">%rsp</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">movq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:teal">blah</span><span style="font-family:"Consolas,",serif;color:black">+</span><span style="font-family:"Consolas,",serif;color:#098658">16</span><span style="font-family:"Consolas,",serif;color:black">(</span><span style="font-family:"Consolas,",serif;color:#4864AA">%rip</span><span style="font-family:"Consolas,",serif;color:black">), </span><span style="font-family:"Consolas,",serif;color:#4864AA">%rax</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">movdqu</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:teal">blah</span><span style="font-family:"Consolas,",serif;color:black">(</span><span style="font-family:"Consolas,",serif;color:#4864AA">%rip</span><span style="font-family:"Consolas,",serif;color:black">), </span><span style="font-family:"Consolas,",serif;color:#4864AA">%xmm0</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">movq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:#4864AA">%rax</span><span style="font-family:"Consolas,",serif;color:black">, </span><span style="font-family:"Consolas,",serif;color:#098658">16</span><span style="font-family:"Consolas,",serif;color:black">(</span><span style="font-family:"Consolas,",serif;color:#4864AA">%rsp</span><span style="font-family:"Consolas,",serif;color:black">)<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">movups</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:#4864AA">%xmm0</span><span style="font-family:"Consolas,",serif;color:black">, (</span><span style="font-family:"Consolas,",serif;color:#4864AA">%rsp</span><span style="font-family:"Consolas,",serif;color:black">)<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">call</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:teal">foo</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">addq</span><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:#3030C0">$40</span><span style="font-family:"Consolas,",serif;color:black">, </span><span style="font-family:"Consolas,",serif;color:#4864AA">%rsp</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"> </span><span style="font-family:"Consolas,",serif;color:blue">ret</span><span style="font-family:"Consolas,",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:#FFFFFE"><span style="font-family:"Consolas,",serif;color:black">Why is clang generating all those instructions (which seem to be just unnecessary
<span style="background:yellow;mso-highlight:yellow">spills</span> of the registers: %rax and %xmm0)?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Consolas"><o:p> </o:p></span></p>
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