> On 09/22/14 08:40, Felix Yang wrote: > > Hi, > > > > I find that update_equiv_regs in ira.c sets the wrong EQUIV > > reg-note for pseudo with more than one definiton in certain situation. > > Here is a simplified RTL snippet after this function finishs handling: > > > > (insn 77 37 78 2 (set (reg:SI 171) > > (const_int 0 [0])) ticket151.c:33 52 {movsi_internal_dsp} > > (expr_list:REG_EQUAL (const_int 0 [0]) > > (nil))) > > > > ...... > > > > (insn 79 50 53 2 (set (mem/c:SI (reg/f:SI 136) [2 g_728+0 S4 A64]) > > (reg:SI 171)) ticket151.c:33 52 {movsi_internal_dsp} > > (expr_list:REG_DEAD (reg:SI 171) > > (nil))) > > (insn 53 79 54 2 (set (mem/c:SI (reg/f:SI 162) [4 g_163+0 S4 A32]) > > (reg:SI 163)) 52 {movsi_internal_dsp} > > (expr_list:REG_DEAD (reg:SI 163) > > (expr_list:REG_DEAD (reg/f:SI 162) > > (nil)))) > > (insn 54 53 14 2 (set (reg:SI 171) > > (mem/u/c:SI (symbol_ref/u:SI ("*.LC8") [flags 0x2]) [4 S4 > > A32])) ticket151.c:49 52 {movsi_internal_dsp} > > (expr_list:REG_EQUIV (mem/u/c:SI (symbol_ref/u:SI ("*.LC8") > > [flags 0x2]) [4 S4 A32]) > > (expr_list:REG_EQUAL (mem/u/c:SI (symbol_ref/u:SI ("*.LC8") > > [flags 0x2]) [4 S4 A32]) > > (nil)))) > > > > > > The REG_EQUIV of insn 54 is not correct as pseudo 171 is defined > > in insn 77 with a differerent value. > > This may causes reload replacing pseudo 171 with mem/u/c:SI > > (symbol_ref/u:SI ("*.LC8"), which is wrong. > > A proposed patch for this issue, please comment: > Is it possible it's the conditional just above this one that is incorrect? > > if (DF_REG_DEF_COUNT (regno) != 1 > && (! note > || rtx_varies_p (XEXP (note, 0), 0) > || (reg_equiv[regno].replacement > && ! rtx_equal_p (XEXP (note, 0), > > reg_equiv[regno].replacement)))) > { > no_equiv (dest, set, NULL); > continue; > } > > > ISTM the only time a multiply-set register can have a valid REG_EQUIV note is > if > each and every assignment to that pseudo has the same RHS. > > Jeff
Thanks Jeff. Yes, I agree that this is a better place to consider. I am thinking of a better way to fix this. Vladimir, can you shed light on this and give me some suggestions? Thank you.