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List:       llvm-bugs
Subject:    [LLVMbugs] [Bug 12420] New: Missed instcombine with pointer differences.
From:       bugzilla-daemon () llvm ! org
Date:       2012-03-30 14:47:25
Message-ID: bug-12420-206 () http ! llvm ! org/bugs/
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http://llvm.org/bugs/show_bug.cgi?id=12420

             Bug #: 12420
           Summary: Missed instcombine with pointer differences.
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
        AssignedTo: unassignedbugs@nondot.org
        ReportedBy: benny.kra@gmail.com
                CC: llvmbugs@cs.uiuc.edu
    Classification: Unclassified


>From GCC PR 21082 (mgrid):

---8<---

typedef __SIZE_TYPE__ size_t;
size_t a[100];
size_t f(size_t b, size_t c)
{
  return &a[b] - &a[c] != b - c;
}

--->8---

Should fold to "false". Looks like something isn't preserving overflow flags.

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