You are experiencing a crash (segfault) ... I'm quite puzzled about the references at both llvm39 and llvm34 libs.
Unless you really need it, please try to remove llvm34.
Code:
[LIST=1]
[*][ 5938.093] (II) glamor: OpenGL accelerated X.org driver based.
[*][ 5938.321] (EE)
[*][ 5938.321] (EE) Backtrace:
[*][ 5938.322] (EE) 0: /usr/local/bin/X (OsInit+0x38a) [0x5abfba]
[*][ 5938.322] (EE) 1: /lib/libthr.so.3 (_pthread_sigmask+0x50d) [0x802daebbd]
[*][ 5938.323] (EE) 2: /lib/libthr.so.3 (_pthread_getspecific+0xe9f) [0x802daeacf]
[*][ 5938.324] (EE) 3: ? (?+0xe9f) [0x800000000032]
[*][ 5938.325] (EE) 4: /usr/local/llvm39/lib/libLLVM-3.9.so (_ZN4llvm13StringMapImpl15LookupBucketForENS_9StringRefE+0x99) [0x8098c02e9]
[*][ 5938.325] (EE) 5: /usr/local/llvm39/lib/libLLVM-3.9.so (LLVMParseCommandLineOptions+0x7cf) [0x80988497f]
[*][ 5938.326] (EE) 6: /usr/local/llvm39/lib/libLLVM-3.9.so (LLVMParseCommandLineOptions+0x92c) [0x809884c1c]
[*][ 5938.327] (EE) 7: /usr/local/llvm39/lib/libLLVM-3.9.so (_ZN4llvm2cl6Option11addArgumentEv+0x7c) [0x809878dec]
[*][ 5938.328] (EE) 8: /usr/local/llvm34/lib/libLLVM-3.4.so (_ZN4llvm16PPCTargetMachine17addAnalysisPassesERNS_6legacy15PassManagerBaseE+0x262) [0x80e5e4ad2]
[*][ 5938.329] (EE) 9: /usr/local/llvm34/lib/libLLVM-3.4.so (LLVMInitializeARMTargetInfo+0x122) [0x80e5eaa84]
[*][ 5938.330] (EE) 10: /usr/local/llvm34/lib/libLLVM-3.4.so (_init+0xe) [0x80d967d44]
[*][ 5938.331] (EE) 11: ? (_rtld_is_dlopened+0x1532) [0x80081a3e2]
[*][ 5938.331] (EE) 12: ? (dlopen+0x191) [0x800816311]
[*][ 5938.332] (EE) 13: /usr/local/lib/libgbm.so.1 (gbm_surface_has_free_buffers+0xf1d) [0x807df55dd]
[*][ 5938.333] (EE) 14: /usr/local/lib/libgbm.so.1 (gbm_surface_has_free_buffers+0xbfb) [0x807df506b]
[*][ 5938.333] (EE) 15: /usr/local/lib/libgbm.so.1 (gbm_surface_has_free_buffers+0x11a) [0x807df39ca]
[*][ 5938.334] (EE) 16: /usr/local/lib/libgbm.so.1 (gbm_create_device+0x39) [0x807df3629]
[*][ 5938.335] (EE) 17: /usr/local/lib/xorg/modules/libglamoregl.so (glamor_egl_init+0x82) [0x807bc7542]
[*][ 5938.335] (EE) 18: /usr/local/lib/xorg/modules/drivers/radeon_drv.so (_init+0x52b22) [0x806faa7c2]
[*][ 5938.336] (EE) 19: /usr/local/lib/xorg/modules/drivers/radeon_drv.so (_init+0x45ae7) [0x806f900e7]
[*][ 5938.337] (EE) 20: /usr/local/bin/X (InitOutput+0xa7f) [0x47f35f]
[*][ 5938.338] (EE) 21: /usr/local/bin/X (remove_fs_handlers+0x38b) [0x43b48b]
[*][ 5938.338] (EE) 22: /usr/local/bin/X (_start+0x17f) [0x42506f]
[*][ 5938.339] (EE) 23: ? (?+0x17f) [0x80083817f]
[*][ 5938.339] (EE)
[*][ 5938.339] (EE) Segmentation fault at address 0x0
[*][ 5938.339] (EE)
[*]Fatal server error:
[*][ 5938.339] (EE) Caught signal 11 (Segmentation fault). Server aborting
[*][ 5938.339] (EE)
[/LIST]