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POProblem with Link Time Optimization causing undefined symbols with ASM constants
 

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  1. POProblem with Link Time Optimization causing undefined symbols with ASM constants
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    <p>I am compiling mplayer with llvm-gcc-4.2.1. </p> <p>With '-O1' (which disables link time optimization), the program successfully compiles and links. With '-O2' or '-O1 -flto', ld complains of undefined symbols:</p> <pre> Undefined symbols for architecture x86_64: "_MM_FIX_0_707106781", referenced from: _filter in vf_fspp.o "_MM_FIX_0_541196100", referenced from: _filter in vf_fspp.o ld: symbol(s) not found for architecture x86_64 collect2: ld returned 1 exit status </pre> <p>fyi, my version of ld: </p> <pre><code>@(#)PROGRAM:ld PROJECT:ld64-123.2 llvm version 2.9svn, from Apple Clang 2.0 (build 137) </code></pre> <p>I'll focus just on MM_FIX_0_707106781, as the other constants all follow the same procedure.</p> <p>MM_FIX_0_707106781 is initialized with the macro: </p> <pre><code>DECLARE_ASM_CONST(8, uint64_t, MM_FIX_0_707106781)=FIX64(0.707106781, 14); </code></pre> <p>which evaluates to: </p> <pre><code>static const uint64_t __attribute__((used, aligned (8))) MM_FIX_0_707106781=0x2d412d412d412d41; </code></pre> <p>These constants are used in asm code:</p> <pre> #define MANGLE(a) "_" #a "(%%rip)" __asm__ volatile( ... "pmulhw "MANGLE(MM_FIX_0_707106781)", %%mm7 \n\t" ... ); </pre> <p>I had a similar (the same?) problem with asm functions that I was able to resolve by adding:<br> <code>".globl "LABLE_MANGLE(functionnamehere)"\n\t"</code><br> before each label, but that knowledge has not helped me with these ASM constants.</p> <p>That is as much information as I can provide, I'm afraid. Once again, with -O1 the code compiles, links, and runs. With -O2 the linker fails to find these asm constants. </p> <p>Can anyone offer a solution to this problem? Thanks.</p>
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