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</o:shapelayout></xml><![endif]--></head><body lang=SV link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Hi all,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span lang=EN-GB>I’m trying to implement mixed 32/64-bit pointers in the same translation unit. But right now, clang is doing something I don’t understand why.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>If I take this simple C++ code:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>#include <cstdint><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>template<typename T><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>using Addr32 = __attribute((address_space(32))) T;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>void Debug(Addr32<int>* p1, int* p2, int* p3, Addr32<int>* p4);<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>Addr32<int> i1 = 1234;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>Addr32<int>* p1;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>int main()<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>{<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB> p1 = &i1;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB> static_assert(sizeof(p1) == 4);<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>}<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>And compile it, I get the following IR without optimizations:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>@"\01?i1@@3HA" = addrspace(32) global i32 1234, align 4<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>@"\01?p1@@3PEAHEA" = global i32 addrspace(32)* null, align 4<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>; Function Attrs: norecurse nounwind uwtable<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>define i32 @main() #0<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>{<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB> store i32 addrspace(32)* @"\01?i1@@3HA", i32 addrspace(32)** @"\01?p1@@3PEAHEA", align 4<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB> ret i32 0<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>}<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>And with optimizations (-O3), it becomes <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>@"\01?i1@@3HA" = addrspace(32) global i32 1234, align 4<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>@"\01?p1@@3PEAHEA" = local_unnamed_addr global i32 addrspace(32)* null, align 8<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>; Function Attrs: norecurse nounwind uwtable<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>define i32 @main() local_unnamed_addr #0<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>{<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB> store i32 addrspace(32)* @"\01?i1@@3HA", i32 addrspace(32)** @"\01?p1@@3PEAHEA", align 8, !tbaa !8<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB> ret i32 0<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>}<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>Both of them produce the same assembly:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>lea rcx, [rip + "?i1@@3HA"]<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>mov qword ptr [rip + "?p1@@3PEAHEA"], rcx<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>So even though I have a 32-bit pointer (static_assert(sizeof(p1) == 4)) and alignment 4 (in the debug version), it gets treated as a 64-bit pointer with alignment 8 in the assembly. Clang also somehow optimizes the pointer by aligning it on a 8-byte boundary when optimizing.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>I’ve overridden TargetInfo::getPointerWidthV and TargetInfo::getPointerAlignV to properly return 32 bits for a pointer in address space 32. I’ve also modified the Pointers vector in the DataLayout to return 4 bytes for both size and alignment for address space 32. Is there something I’m missing? Why is clang treating the pointers as 64 bits?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal style='margin-top:12.0pt;page-break-after:avoid'><span style='font-size:12.0pt;font-family:"Calibri Light",sans-serif;color:#A5A5A5;mso-fareast-language:SV'>Regards,<o:p></o:p></span></p><p class=MsoNormal style='page-break-after:avoid'><span style='font-size:12.0pt;font-family:"Calibri Light",sans-serif;color:#A5A5A5;mso-fareast-language:SV'>Patrik Eklöf<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p></div></body></html>