https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105231
--- Comment #21 from Eric Botcazou <ebotcazou at gcc dot gnu.org> --- > I'm not sure that's a general enough fix though since we seem to drop > the REG_EQUAL note and as soon as we do that there's a disconnect > between what CFG generation thinks throws and what combine thinks > is good enough to put a REG_EH_REGION note on. Yes, we actually drop 2 REG_EQUAL notes: (insn 22 17 78 3 (set (reg:SF 92) (mem/u/c:SF (symbol_ref/u:SI ("*.LC0") [flags 0x2]) [0 S4 A32])) "pr105231.c":6:3 142 {*movsf_internal} (expr_list:REG_EQUAL (const_double:SF 1.8446744073709551616e+19 [0x0.8p+65]) (nil))) (insn 78 22 24 3 (set (reg:XF 99) (float_extend:XF (reg:SF 92))) 166 {*extendsfxf2_i387} (expr_list:REG_DEAD (reg:SF 92) (expr_list:REG_EQUAL (const_double:XF 1.8446744073709551616e+19 [0x0.8p+65]) (nil)))) --> (insn 78 22 24 3 (set (reg:XF 99) (float_extend:XF (mem/u/c:SF (symbol_ref/u:SI ("*.LC0") [flags 0x2]) [0 S4 A32]))) 166 {*extendsfxf2_i387} (expr_list:REG_EH_REGION (const_int 1 [0x1]) (nil))) so an immediate solution would be to preserve the one on insn 78 (and arrange for the purge_dead_edge magic to trigger again).