[Bug target/41505] GCC choosing poor code sequence for certain stores (x86)

[jakub at gcc dot gnu dot org]

------- Comment #6 from jakub at gcc dot gnu dot org  2009-09-30 09:22 -------
For x86-64 we perhaps want further checks for the size optimization - if the
scratch register is %r8d through %r15d, 3 byte xorl %r8d, %r8d and e.g. 3 byte
movl %r8d, (%rdx) won't be shorter than movl $0, (%rdx) which is 6 bytes).
And likely the 2 insns will be slower.
But if the address already needs rex prefix, it is still a win.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41505