[llvm-bugs] [Bug 44605] New: [SCEV] ScalarEvolution may generate wrong result for PHI depending on another PHI

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=44605

            Bug ID: 44605
           Summary: [SCEV] ScalarEvolution may generate wrong result for
                    PHI depending on another PHI
           Product: libraries
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Global Analyses
          Assignee: unassignedbugs at nondot.org
          Reporter: dantrushin at gmail.com
                CC: llvm-bugs at lists.llvm.org

IndVarSimplify miscompiles the attached testcase due to ScalarEvolution 
computing wrong exit value for PHI node %local_3_4

outer:
  %local_6_6 = phi i32 [ 10, %entry ], [ %5, %latch ]
  %local_4_5 = phi i32 [ 56587, %entry ], [ %.udiv, %latch ]
  %local_3_4 = phi i32 [ 2, %entry ], [ %local_6_6, %latch ]

<snip>

latch:
  %.lcssa = phi i32 [ %2, %inner ]
  %5 = add nuw nsw i32 %local_6_6, 1
  %6 = icmp ugt i32 %local_6_6, 276
  br i1 %6, label %return, label %outer

Exit value of %local_3_4 is computed as equal to exit value of %local_6_6,
while in fact it is one less (uses previous value of %local_6_6)

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