[Bug tree-optimization/68413] [6 Regression] internal compiler error: in vect_transform_stmt

[ienkovich at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68413

--- Comment #6 from Ilya Enkovich <ienkovich at gcc dot gnu.org> ---
I checked what is happening and seems the reason is in different
STMT_VINFO_VEC_REDUCTION_TYPE (stmt_info) on analysis and transform phases. 
During analysis it is INTEGER_INDUC_COND_REDUCTION, for transformation it is
COND_REDUCTION.

Thus we have different flow for if-statement at tree-vect-loop.c:5653 whose
branches have two major differences.

1. Different types are used to get optab.  For analysis we get
reduc_smax_scal_optab, for transformation we get reduc_umax_scal_optab.

2. Only 'true path' checks old optabs (with no _scal_)

This bug was 'fixed' by r230423 which switched i386 target to new optabs, but
problem still exist.  Currently I see on trunk:

Analysis:
#0  optab_handler (op=reduc_smax_scal_optab, mode=V8SImode) at
gcc/optabs-query.h:31
#1  0x0000000001023d5d in vectorizable_reduction (stmt=0x7ffff7f20660, gsi=0x0,
vec_stmt=0x0, slp_node=0x0) at gcc/tree-vect-loop.c:5643

Transformation:
#0  optab_handler (op=reduc_umax_scal_optab, mode=V8SImode) at
gcc/optabs-query.h:31
#1  0x0000000001023fb1 in vectorizable_reduction (stmt=0x7ffff7f20660,
gsi=0x7fffffffb600, vec_stmt=0x7fffffffb558, slp_node=0x0) at
gcc/tree-vect-loop.c:5691

Note the same statements but different optabs used.

Also we my still have ICE on targets not using new reduction optabs.