[Bug tree-optimization/61929] Graphite: Banerjee and Omega differ on distance vectors (internal compiler error in compute_affine_dependence)

[gcc at crg4 dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61929

--- Comment #4 from Charles Greathouse <gcc at crg4 dot com> ---
I now have a testcase for failure with -floop-parallelize-all (without
-fcheck-data-deps). I believe this is the same bug, or at least related,
because this testcase also fails with the previous compile command.

int main() {}
void generateICE2(char *s, int i)
{
    for (; i >= 2; i--) s[i] = s[i-1];
}

This fails with

gcc testcase.c -lm -O2 -floop-parallelize-all -floop-nest-optimize

or even

gcc testcase.c -lm -O2 -floop-parallelize-all -floop-nest-optimize
-fno-aggressive-loop-optimizations -fno-align-functions -fno-align-jumps
-fno-align-labels -fno-align-loops -fno-asynchronous-unwind-tables
-fno-branch-count-reg -fno-caller-saves -fno-combine-stack-adjustments
-fno-common -fno-compare-elim -fno-cprop-registers -fno-crossjumping
-fno-cse-follow-jumps -fno-dce -fno-defer-pop -fno-delete-null-pointer-checks
-fno-devirtualize -fno-dse -fno-early-inlining -fno-expensive-optimizations
-fno-forward-propagate -fno-gcse -fno-gcse-lm -fno-guess-branch-probability
-fno-hoist-adjacent-loads -fno-if-conversion -fno-if-conversion2 -fno-inline
-fno-inline-atomics -fno-inline-functions-called-once
-fno-inline-small-functions -fno-ipa-cp -fno-ipa-profile -fno-ipa-pure-const
-fno-ipa-reference -fno-ipa-sra -fno-ira-hoist-pressure -fno-ivopts
-fno-jump-tables -fno-math-errno -fno-merge-constants -fno-move-loop-invariants
-fno-optimize-register-move -fno-optimize-sibling-calls -fno-optimize-strlen
-fno-peephole -fno-peephole2 -fno-prefetch-loop-arrays -fno-regmove
-fno-rename-registers -fno-reorder-blocks -fno-reorder-functions
-fno-rerun-cse-after-loop -fno-sched-critical-path-heuristic
-fno-sched-dep-count-heuristic -fno-sched-group-heuristic -fno-sched-interblock
-fno-sched-last-insn-heuristic -fno-sched-rank-heuristic -fno-sched-spec
-fno-sched-spec-insn-heuristic -fno-sched-stalled-insns-dep
-fno-schedule-insns2 -fno-set-stack-executable -fno-short-enums
-fno-shrink-wrap -fno-signed-zeros -fno-split-ivs-in-unroller
-fno-split-wide-types -fno-strict-aliasing -fno-thread-jumps -fno-trapping-math
-fno-tree-bit-ccp -fno-toplevel-reorder -fno-tree-builtin-call-dce
-fno-tree-ccp -fno-tree-coalesce-vars -fno-tree-copy-prop -fno-tree-copyrename
-fno-tree-cselim -fno-tree-dce -fno-tree-dominator-opts -fno-tree-dse
-fno-tree-forwprop -fno-tree-fre -fno-tree-loop-if-convert -fno-tree-loop-im
-fno-tree-loop-ivcanon -fno-tree-phiprop -fno-tree-pre -fno-tree-pta
-fno-tree-reassoc -fno-tree-scev-cprop -fno-tree-sink -fno-tree-slp-vectorize
-fno-tree-slsr -fno-tree-sra -fno-tree-switch-conversion -fno-tree-tail-merge
-fno-tree-ter -fno-tree-vect-loop-version -fno-tree-vrp -fno-unit-at-a-time
-fno-var-tracking -fno-var-tracking-assignments -fno-web

which is -O2 with everything but floop-parallelize-all -floop-nest-optimize
-ftree-loop-optimize -ftree-ch -fthreadsafe-statics turned off. However the bug
does not appear at -O1 and below even with these options.