[Bug tree-optimization/23455] load PRE is missing

[bonzini at gcc dot gnu dot org]

------- Additional Comments From bonzini at gcc dot gnu dot org  2005-08-18 13:46 -------
Sorry.

outcnt aliases with outbuf, so the load of t2 cannot be removed.  The GIMPLE
code that is now emitted is something like:


    void
    bi_windup(unsigned char *outbuf, unsigned char bi_buf)
    {
        int t1 = outcnt;
        outbuf[t1] = bi_buf;
        int t2 = outcnt;
        if (t2 == 16384)
                flush_outbuf();
	int t3 = outcnt;
        outbuf[t3] = bi_buf;
    }

where t3 == t2 if flush_outbuf is not called.  My code removes the load into t3
if flush_outbuf is not called.

 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23455