<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>The attached code is miscompiled when targeting big-endian AArch64 at all optimisation levels except for -O0. This should print "checksum = 00000008", but actually prints "checksum = 00000000". It is correctly compiled if I change the statement just before the function call from l_15.f0 to l_15.f1 (the result of this expression is unused). The only change this causes in the IR is to change the parameter in the call to func_13 from 0x800000180 to 0x800018000.<br><br>The problem seems to be in llvm/lib/Transforms/Scalar/SROA.cpp. The ‘Scalar Replacement Of Aggregates’ pass takes into account endianness, thus adds a shift instruction when inserting an integer to an alloca store:<o:p></o:p></p><p class=MsoNormal> if(DL.isBigEndian())<o:p></o:p></p><p class=MsoNormal> ShAmt = 8 * (DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);<o:p></o:p></p><p class=MsoNormal>In this particular example an integer value of wrong size ({i32}) is passed as parameter to the function that computes the shift amount (‘insertInteger’). This causes a zero shift amount since IntTy = {i64}, Ty = {i32}, and offset = 4 bytes. My patch passes a parameter of Ty = {i24} to ‘insertInteger’.<o:p></o:p></p><p class=MsoNormal><br>Alexandros Lamprineas<o:p></o:p></p></div></body></html>