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<p class="MsoNormal">I’m just diving into LLVM. What does it mean when LoadInst::getAlignment() returns 0? Unknown alignment, use default alignment of the type for the load, something else?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In particular, clang appears to set to 0 the alignment of the load instruction that results from accessing the lvalue returned by a call. Is this the intended behavior?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For example:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">const double &foo(void *p);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">double ans;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">void bar()<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">{<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> ans = foo(0);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">}<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Produces:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">2:32:32-f64:64:64-v64:64:64-v128:64:128-a0:0:64-n32-S64"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">target triple = "armv4t---eabi"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">@ans = global double 0.000000e+00, align 8<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">define void @_Z3barv() {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">entry:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> %call = call double* @_Z3fooPv(i8* null)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> %0 = load double* %call<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> store double %0, double* @ans, align 8<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> ret void<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">declare double* @_Z3fooPv(i8*)<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Notice that the load does not have an alignment specification.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks for your help,<o:p></o:p></p>
<p class="MsoNormal">Jon<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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