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if_then_else usage in attribute computation
- From: Ilya Enkovich <enkovich dot gnu at gmail dot com>
- To: gcc at gcc dot gnu dot org
- Date: Tue, 23 Jul 2013 15:01:42 +0400
- Subject: if_then_else usage in attribute computation
Hi,
Recently I found a weird behavior in attribute computation when
if_then_else is used. It may be easily demonstrated on i386 jump
instruction. It's original length attribute definition is following:
(set (attr "length")
(if_then_else (and (ge (minus (match_dup 0) (pc))
(const_int -126))
(lt (minus (match_dup 0) (pc))
(const_int 128)))
(const_int 2)
(const_int 5)))
I change it keeping the same resulting values:
(set (attr "length")
(if_then_else (and (ge (minus (match_dup 0) (pc))
(const_int -126))
(lt (minus (match_dup 0) (pc))
(const_int 128)))
(plus (const_int 2) (const_int 0))
(plus (const_int 5) (const_int 0))))
After that change I see in assembler:
jmp .L2 # 412 jump [length = 2147483647]
It also causes fails in make check because some optimizations work in
a different way when size changes.
I tried to debug it and found that insn_current_length function always
return correct values when called for jump insn.
Seems problem always occurs when 'if_then_else' or 'cond' is combined
with 'plus'. Is such combination supposed to work?
Thanks,
Ilya