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[Bug rtl-optimization/60533] [4.8/4.9 regression] Error introduced by bb-reorder at -O3
- From: "ebotcazou at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sat, 15 Mar 2014 10:38:40 +0000
- Subject: [Bug rtl-optimization/60533] [4.8/4.9 regression] Error introduced by bb-reorder at -O3
- Auto-submitted: auto-generated
- References: <bug-60533-4 at http dot gcc dot gnu dot org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60533
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2014-03-15
Ever confirmed|0 |1
--- Comment #5 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Following bb-reorder, insns 266 and 268 are now in block 12, but insn 283 is
> in block 87, a great distance away. As a result, r6 is now upward exposed
> by insn 283 in block 87, which has blocks 12 and 86 as predecessors. Block
> 86 ends with a call in insn 887, which clobbers the volatile register r6.
> So along the path from block 86 to block 87, insn 283 is guaranteed to see
> garbage in r6.
>
> There is nothing in the prior graph corresponding to a path from block 86 to
> block 87; this bogus path was introduced by the block reordering.
Right, because there is a barrier right after the call in the prior graph:
(call_insn 887 885 888 109 (parallel [
(set (reg:DI 3 3)
(call (mem:SI (symbol_ref/i:DI
("_ZN5vigra6detail14UnionFindArrayIiE9makeUnionEii") [flags 0x1]
<function_decl 0x1ffffbc04a00 makeUnion>) [0 makeUnion S4 A8])
(const_int 0 [0])))
(clobber (reg:DI 65 lr))
])
/home/ubuntu/libvigraimpex/ubuntu1/libvigraimpex-1.10.0+dfsg/include/vigra/labelvolume.hxx:287
625 {*call_value_nonlocal_aixdi}
(expr_list:REG_DEAD (reg:DI 5 5)
(expr_list:REG_DEAD (reg:DI 4 4)
(expr_list:REG_DEAD (reg:DI 2 2)
(expr_list:REG_UNUSED (reg:DI 3 3)
(expr_list:REG_EH_REGION (const_int 0 [0])
(nil))))))
(expr_list:REG_DEP_TRUE (use (reg:DI 2 2))
(expr_list:REG_LABEL_TARGET (use (reg:DI 5 5))
(expr_list:REG_LABEL_TARGET (use (reg:DI 4 4))
(expr_list:REG_LABEL_OPERAND (use (reg:DI 3 3))
(nil))))))
(barrier 888 887 889)
so the compiler thinks that the call never returns. Can you find out why?