(SPARC) Specify code address space.
The following table lists the values for v.
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The default is -xcode=abs32 for 32–bit architectures. The default for 64–bit architectures is-xcode=abs44.
When building shared dynamic libraries, the default -xcode values of abs44 and abs32 will not work with 64–bit architectures. Specify -xcode=pic13 or -xcode=pic32 instead. Two nominal performance costs with -xcode=pic13 and -xcode=pic32 on SPARC are:.
A routine compiled with either -xcode=pic13 or -xcode=pic32 executes a few extra instructions upon entry to set a register to point at a table (_GLOBAL_OFFSET_TABLE_) used for accessing a shared library’s global or static variables.
Each access to a global or static variable involves an extra indirect memory reference through _GLOBAL_OFFSET_TABLE_. If the compilation includes -xcode=pic32, there are two additional instructions per global and static memory reference.
When considering these costs, remember that the use of -xcode=pic13 and -xcode=pic32 can significantly reduce system memory requirements due to the effect of library code sharing. Every page of code in a shared library compiled -xcode=pic13 or -xcode=pic32 can be shared by every process that uses the library. If a page of code in a shared library contains even a single non-pic (that is, absolute) memory reference, the page becomes nonsharable, and a copy of the page must be created each time a program using the library is executed.
The easiest way to tell whether a .o file has been compiled with -xcode=pic13 or -xcode=pic32 is by using the nm command:
% nm file.o | grep _GLOBAL_OFFSET_TABLE_ U _GLOBAL_OFFSET_TABLE_
A .o file containing position-independent code contains an unresolved external reference to _GLOBAL_OFFSET_TABLE_, as indicated by the letter U.
To determine whether to use -xcode=pic13 or -xcode=pic32, check the size of the Global Offset Table (GOT) by using elfdump -c looking for the section header sh_name: .got. The sh_size value is the size of the GOT. If the GOT is less than 8,192 bytes, specify -xcode=pic13. Otherwise specify -xcode=pic32.See the elfdump(1) man page for more information.
Follow these guidelines to determine how you should use -xcode:
If you are building an executable, do not use -xcode=pic13 or -xcode=pic32.
If you are building an archive library only for linking into executables, do not use -xcode=pic13 or -xcode=pic32.
If you are building a shared library, start with -xcode=pic13 and, once the GOT size exceeds 8,192 bytes, use -xcode=pic32.
If you are building an archive library for linking into shared libraries, use -xcode=pic32.