[Bug rtl-optimization/16802] PowerPC - Unnecessary extsw

[nathan at gcc dot gnu dot org]

------- Additional Comments From nathan at gcc dot gnu dot org  2004-11-03 11:29 -------
I believe this is a problem with the tree optimizers being ABI blind. on 64bit
ppc integral parameters and return values are correctly extended to 64 bits.  This
sign extension is inserted during the tree->rtl translation, and therefore
cannot leverage any ssa-vrp information.  Unfortunately RTL does not have VRP
itself, but only condition-code propagation.  Combine does not track values
across basic blocks, so it too is blind in this case, as the register is
written in two blocks.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16802