[LLVMbugs] [Bug 11240] New: redundant new/delete pair not removed

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=11240

           Summary: redundant new/delete pair not removed
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: richard-llvm at metafoo.co.uk
                CC: llvmbugs at cs.uiuc.edu


Created an attachment (id=7535)
 --> (http://llvm.org/bugs/attachment.cgi?id=7535)
Reduced testcase

The attached IR has a redundant new/delete pair (for %alloc1, whose only other
use is a dead store). The code has been manually reduced from this (compiled
with a large inlining threshold):

#include <vector>
void resize() {
  std::vector<int> v;
  v.push_back(1);
  v.push_back(2);
  // ...
}

The optimizer is unable to remove this new/delete pair. The outcome seems to be
quite sensitive to the other instructions in the IR: the optimization did fire
in various partially-reduced testcases containing this IR plus some other
seemingly-irrelevant instructions.

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