[Bug rtl-optimization/49028] Missed optimization of pointer arithmetic

[piotr.wyderski at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49028

--- Comment #1 from Piotr Wyderski <piotr.wyderski at gmail dot com> 2011-05-17 17:24:03 UTC ---
If I change the function to:

template <unsigned int N> void R<N>::xxx_release(void* p) {

    char* q = reinterpret_cast<char*>(m_Cursor);
       char* b = reinterpret_cast<char*>(m_Data);

       q = ((q + sizeof(void*)) - b) % (N * sizeof(void*)) + b;
    m_Cursor = reinterpret_cast<void**>(q);
    *m_Cursor = p;
}

Then the generated code is:

000000000041a910 <_ZN1RILj16EE11xxx_releaseEPv>:
  41a910:    48 8b 87 80 00 00 00     mov    0x80(%rdi),%rax
  41a917:    48 83 c0 08              add    $0x8,%rax
  41a91b:    48 29 f8                 sub    %rdi,%rax
  41a91e:    83 e0 7f                 and    $0x7f,%eax
  41a921:    48 01 f8                 add    %rdi,%rax
  41a924:    48 89 87 80 00 00 00     mov    %rax,0x80(%rdi)
  41a92b:    48 89 30                 mov    %rsi,(%rax)
  41a92e:    c3                       retq   

which is astonishingly close to my hand-made assembly...