On Sep 20, 2006, at 10:40 PM, Naveen Neelakantam wrote:
Very clever! It seems like an array bounds check is converted into
an unsigned comparison followed by a JNB on Ia32. This single
compare-and-branch sequence correctly implements both the upper
bound and lower bound checks. Because the comparison is unsigned,
a negative index will look like a very large positive index and
will fail the check.
Isn't that really just "faith based"? What if you really do have a
very large upper bound?
Naveen
On Sep 20, 2006, at 4:06 PM, Naveen Neelakantam wrote:
Hello,
It seems that the Op_TauCheckBounds opcode in the HIR is converted
into an upper bounds check during HIR->LIR conversion (see
CodeGenerator.cpp and Ia32InstCodeSelector.cpp). It does not seem
that the corresponding lower bounds check is ever generated.
Am I misunderstanding the code somehow? It doesn't seem correct
to me.
Thanks,
Naveen
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