[webkit-dev] jit, unordered compare

Zoltan Herczeg zherczeg at inf.u-szeged.hu
Mon Oct 12 04:05:29 PDT 2009


My stougle with USE_JSVALUE32_64 still continues on ARM. In
emit_op_jfalse, there is a comparison here (fpRegT0 contains 0.0):
 addJump(branchDouble(DoubleEqual, fpRegT0, fpRegT1), target + 2);

In x86, if either operand is NaN, the zero flag is set by definition
(ucomisd instruction). I have no idea why (NaN == anything is true?).
Unfortunately, ARM does not set the zero flag. What would be a portable
way to improve this instruction? (and emit_op_jtrue) Perhaps this affects
the possible thumb2 implementation with USE_JSVALUE32_64 as well.


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