[llvm-bugs] [Bug 52087] New: Failure to optimize out dead part of store when followed by smaller overlapping store

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=52087

            Bug ID: 52087
           Summary: Failure to optimize out dead part of store when
                    followed by smaller overlapping store
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: gabravier at gmail.com
                CC: llvm-bugs at lists.llvm.org

void foo(char *__restrict a, char *__restrict b, char *__restrict c)
{
  memcpy(a, b, 128);
  memcpy(a, c, 64);
}

This can be optimized to this:

void foo2(char *__restrict a, char *__restrict b, char *__restrict c)
{
  memcpy(a + 64, b + 64, 64);
  memcpy(a, c, 64);
}

This optimization is done by GCC, but not by LLVM.

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