[Bug tree-optimization/33319] New: ICE with vectorization in

["dorit at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

when the testcase g++.dg/tree-ssa/pr27549.C is compiled with -ftree-vectorize
it ICEs with: 

Unable to coalesce ssa_names 141 and 280 which are marked as MUST COALESCE.
s$b_141(ab) and  s$b_280(ab)
/Develop/mainline-dn/gcc/gcc/testsuite/g++.dg/tree-ssa/pr27549.C: In function
âconst char* foo()â:
/Develop/mainline-dn/gcc/gcc/testsuite/g++.dg/tree-ssa/pr27549.C:72: internal
compiler error: SSA corruption

The testcase is vectorized using versioning-for-aliasing, although it is known
at compile time that there is a dependence for sure, so there's no point in
testing this at runtime (as pointed out here:
http://gcc.gnu.org/ml/gcc-patches/2007-08/msg01211.html). With --param
vect-max-version-for-alias-checks=0 the testcase doesn't get vectorized and
doesn't ICE. So, Disabling versioning-for-aliasing when it's redundant (like in
the above case) would avoid the ICE, but we should probably figure out what is
really causing the ICE.

(this is how the testcase is compiled:
/Develop/mainline-dn/build1/gcc/testsuite/g++/../../g++
-B/Develop/mainline-dn/build1/gcc/testsuite/g++/../../
/Develop/mainline-dn/gcc/gcc/testsuite/g++.dg/tree-ssa/pr27549.C -nostdinc++
-I/Develop/mainline-dn/build1/powerpc64-unknown-linux-gnu/libstdc++-v3/include/powerpc64-unknown-linux-gnu
-I/Develop/mainline-dn/build1/powerpc64-unknown-linux-gnu/libstdc++-v3/include
-I/Develop/mainline-dn/gcc/libstdc++-v3/libsupc++
-I/Develop/mainline-dn/gcc/libstdc++-v3/include/backward
-I/Develop/mainline-dn/gcc/libstdc++-v3/testsuite/util -fmessage-length=0 -O2
-S -m64 -O2 -ftree-vectorize -maltivec -fdump-tree-vect-details -o pr27549.s)


-- 
           Summary: ICE with vectorization in
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dorit at gcc dot gnu dot org
 GCC build triplet: powerpc-linux
  GCC host triplet: powerpc-linux
GCC target triplet: powerpc-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33319