[Bug tree-optimization/69341] New: [6 Regression] [graphite] ICE: verify_ssa failed (error: definition in block 37 does not dominate use in block 30)

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69341

            Bug ID: 69341
           Summary: [6 Regression] [graphite] ICE: verify_ssa failed
                    (error: definition in block 37 does not dominate use
                    in block 30)
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

At least gcc-6.0.0-alpha20160110 and gcc-6.0.0-alpha20160117 snapshots ICE when
compiling the following reduced snippet w/ -O2 -floop-interchange:

int pz, s1 = 0;
int lp[2];
static int mj[2] = { 0 };

void
u9(void)
{
  while (s1 < 1) {
    for (pz = 0; pz < 2; ++pz)
      lp[pz] = mj[pz];
    ++s1;
  }
}

% x86_64-pc-linux-gnu-gcc-6.0.0-alpha20160117 -c -O2 -floop-interchange
o9fbslmk.c                               
o9fbslmk.c: In function 'u9':
o9fbslmk.c:6:1: error: definition in block 37 does not dominate use in block 30
 u9(void)
 ^~

for SSA_NAME: pretmp_25 in statement:
prephitmp_2 = PHI <0(24), pretmp_25(30)>
PHI argument
pretmp_25
for PHI node
prephitmp_2 = PHI <0(24), pretmp_25(30)>
o9fbslmk.c:6:1: internal compiler error: verify_ssa failed

Maybe this is related to PR68692, where segfault shadows an apparently similar
issue.