Basically, we have
before PRE:
<bb 3>:
# c_92 = PHI <c_88(19), c_6(23)>;
<L1>:;
# VUSE <SMT.18086_30>;
D.571515_36 = fieldEngineBase_5->stride_m;
D.571516_37 = m_104 * D.571515_36;
D.571517_38 = c_92 + D.571516_37;
# VUSE <SMT.18086_30>;
D.571521_46 = fieldEngineBase_5->data_m.blockControllerPtr_m.ptr_m;
# VUSE <SMT.18091_148>;
D.571523_49 = D.571521_46->pBegin_m;
# VUSE <SMT.18086_30>;
D.571527_54 = fieldEngineBase_5->data_m.offset_m;
after PRE:
NOTE: no flow-sensitive alias info for pretmp.18109_51 in pretmp.18111_48 =
pretmp.18109_51->pBegin_m;
<bb 23>:
<L48>:;
# VUSE <SMT.18086_30>;
pretmp.18106_60 = fieldEngineBase_5->stride_m;
pretmp.18108_52 = pretmp.18106_60 * m_104;
# VUSE <SMT.18086_30>;
pretmp.18109_51 = fieldEngineBase_5->data_m.blockControllerPtr_m.ptr_m;
pretmp.18111_48 = pretmp.18109_51->pBegin_m;
# VUSE <SMT.18086_30>;
pretmp.18113_35 = fieldEngineBase_5->data_m.offset_m;
note the missing # VUSE <SMT.18091_148>; on the dereference of
pretmp.18109_51. verify_ssa only detects this later after loopinit
which adds back the VUSE, but with a bare unrenamed SMT.18091.
Oh, this may be the n-th dup of the same problem - just I didn't see PRE
mentioned sofar. And no, I don't have a (small) testcase yet - this
is in compiling tramp3d-v5 with custom patches.
--
Summary: PRE looses SMT alias info
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: rguenth at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27086
