http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49798
--- Comment #15 from H.J. Lu <hjl.tools at gmail dot com> 2011-07-21 17:24:01 UTC --- Another example: [hjl@gnu-6 pr49798]$ cat y.i union U { int *m; long long d; }; extern int xxxx; long long foo () { union U v = { &xxxx}; return v.d; } [hjl@gnu-6 pr49798]$ /export/build/gnu/gcc/build-x86_64-linux/gcc/xgcc -B/export/build/gnu/gcc/build-x86_64-linux/gcc/ -S -o y.s -mx32 -O -msse4 y.i -da [hjl@gnu-6 pr49798]$ cat y.s .file "y.i" .text .globl foo .type foo, @function foo: .LFB0: .cfi_startproc movl $xxxx, %eax ret .cfi_endproc .LFE0: .size foo, .-foo .ident "GCC: (GNU) 4.7.0 20110720 (experimental)" .section .note.GNU-stack,"",@progbits [hjl@gnu-6 pr49798]$ cat y.i.223r.final ;; Function foo (foo, funcdef_no=0, decl_uid=1711, cgraph_uid=0) (note 1 0 3 NOTE_INSN_DELETED) (note 3 1 24 2 [bb 2] NOTE_INSN_BASIC_BLOCK) (note 24 3 2 2 NOTE_INSN_PROLOGUE_END) (note 2 24 17 2 NOTE_INSN_FUNCTION_BEG) (insn 17 2 20 2 (set (reg/i:DI 0 ax) (symbol_ref:DI ("xxxx") [flags 0x40] <var_decl 0x7ffdb52bb140 xxxx>)) y.i:12 62 {*movdi_internal_rex64} (nil)) (insn 20 17 25 2 (use (reg/i:DI 0 ax)) y.i:12 -1 (nil)) (note 25 20 26 2 NOTE_INSN_EPILOGUE_BEG) (jump_insn 26 25 27 2 (return) y.i:12 645 {return_internal} (nil)) (barrier 27 26 23) (note 23 27 0 NOTE_INSN_DELETED) [hjl@gnu-6 pr49798]$