Hello! The allocator function does mention "cleared".
2012-11-06 Uros Bizjak <ubiz...@gmail.com> * config/i386/i386.c (ix86_init_machine_status): Do not explicitly clear tls_descriptor_call_expanded_p again. Tested on x86_64-pc-linux-gnu {,-m32}, committed to mainline SVN, will be backported to 4.7. Uros. Index: i386.c =================================================================== --- i386.c (revision 193244) +++ i386.c (working copy) @@ -23415,7 +23417,6 @@ ix86_init_machine_status (void) f = ggc_alloc_cleared_machine_function (); f->use_fast_prologue_epilogue_nregs = -1; - f->tls_descriptor_call_expanded_p = 0; f->call_abi = ix86_abi; f->optimize_mode_switching[AVX_U128] = TARGET_VZEROUPPER;