Let me revive this thread and ask for suggestions/tips on the issue below.
Cheers, PMatos On 16/03/11 18:19, Paulo J. Matos wrote:
Hi, I have touched this subject before: http://thread.gmane.org/gmane.comp.gcc.devel/116198/focus=116200 Now, at the time I didn't pursue this issue but now with 4.4.4 this keeps happening and I traced it to the cprop_hardreg replacing a register which makes the set insn having the same source and dest. Here's insn 32 from pass 183:ce3 (insn 32 31 33 4 h.c:51 (set (reg:QI 1 AL) (reg/f:QI 8 @H'fff9 [33])) 4 {*movqi} (expr_list:REG_DEAD (reg/f:QI 8 @H'fff9 [33]) (expr_list:REG_EQUAL (plus:QI (reg/f:QI 6 Y) (const_int 1 [0x1])) (nil)))) Now the same insn after the following pass 185:cprop_hardreg insn 32: replaced reg 8 with 1 ... (insn 32 31 33 4 h.c:51 (set (reg:QI 1 AL) (reg/f:QI 1 AL [33])) 4 {*movqi} (expr_list:REG_DEAD (reg/f:QI 8 @H'fff9 [33]) (expr_list:REG_EQUAL (plus:QI (reg/f:QI 6 Y) (const_int 1 [0x1])) (nil)))) This stays as is until assembler generation, which is really annoying cause it generates an instruction (which is basically a nop) like: ... mov AL,AL ... Is this a known issue? I can't see how this is a problem with my backend but might as well be. Maybe cprop_regmove should check if it is making the src equal to dest and if it is remove the insn? Any suggestions? -- PMatos
