http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58831
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Component|tree-optimization |rtl-optimization --- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- It's instruction scheduling which in fn1 changes .L8: movq $d, (%rsi) movq $d, b(%rip) cmpq $0, r(%rip) je .L15 // assert-fail to .L8: cmpq $0, r(%rip) movq $d, (%rsi) movq $d, b(%rip) je .L15 but %rsi points to r. Before sched2 we have (note 22 21 23 4 [bb 4] NOTE_INSN_BASIC_BLOCK) (insn 23 22 24 4 (set (mem/f:DI (reg/v/f:DI 4 si [orig:90 p2 ] [90]) [3 *p2_9(D)+0 S8 A64]) (symbol_ref:DI ("d") <var_decl 0x7f8900812720 d>)) t.c:12 85 {*movdi_internal} (expr_list:REG_DEAD (reg/v/f:DI 4 si [orig:90 p2 ] [90]) (nil))) (insn 24 23 25 4 (set (mem/f/c:DI (symbol_ref:DI ("b") <var_decl 0x7f89008125f0 b>) [3 b+0 S8 A64]) (symbol_ref:DI ("d") <var_decl 0x7f8900812720 d>)) t.c:12 85 {*movdi_internal} (nil)) (insn 25 24 26 4 (set (reg:CCZ 17 flags) (compare:CCZ (mem/f/c:DI (symbol_ref:DI ("r") <var_decl 0x7f8900812a18 r>) [3 r+0 S8 A64]) (const_int 0 [0]))) t.c:14 4 {*cmpdi_ccno_1} (nil)) (jump_insn 26 25 35 4 (set (pc) seems to be dependent on code-changes in random places :/ Somewhat shorter testcase: #include<assert.h> int a, *b, c, d, f, **i, p, q, *r; short o, j; static int __attribute__((noinline, noclone)) fn1 (int *p1, int **p2) { int **e = &b; for (; p; p++) *p1 = 1; *e = *p2 = &d; assert (r); return c; } static int ** __attribute__((noinline, noclone)) fn2 () { for (f = 0; f != 42; f++) { int *g[3] = {0, 0, 0}; for (o = 0; o; o--) for (; a > 1;) { int **h[1] = { &g[2] }; } } return &r; } int main () { i = fn2 (); fn1 (b, i); return 0; }