Re: [drlvm][jit] array bounds check implementation
Hello, Egor, Isn't that really just faith based? What if you really do have a very large upper bound? upper bounds are not larger than Integer.MAX_VALUE, and any negative value in unsigned arithmetic is larger. I love this hack. Maybe it's worth to comment it and other tricks like this? Seems it's not too obvious :) -- Regards, Anton Luht, Intel Middleware Products Division - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: [drlvm][jit] array bounds check implementation
On Sep 21, 2006, at 8:01 AM, Anton Luht wrote: Hello, Egor, Isn't that really just faith based? What if you really do have a very large upper bound? upper bounds are not larger than Integer.MAX_VALUE, and any negative value in unsigned arithmetic is larger. I love this hack. Maybe it's worth to comment it and other tricks like this? Seems it's not too obvious :) I agree. As long as you are utterly convinced that this hack won't fail (rather than it be highly unlikely), sure... -- Regards, Anton Luht, Intel Middleware Products Division - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: [drlvm][jit] array bounds check implementation
On Sep 21, 2006, at 5:01 AM, Anton Luht wrote: Hello, Egor, Isn't that really just faith based? What if you really do have a very large upper bound? upper bounds are not larger than Integer.MAX_VALUE, and any negative value in unsigned arithmetic is larger. I love this hack. Maybe it's worth to comment it and other tricks like this? Seems it's not too obvious :) Yes please! - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
[drlvm][jit] array bounds check implementation
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 - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: [drlvm][jit] array bounds check implementation
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. 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 - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: [drlvm][jit] array bounds check implementation
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 - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: harmony-dev- [EMAIL PROTECTED] - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: [drlvm][jit] array bounds check implementation
On the 0x1EB day of Apache Harmony Geir Magnusson, Jr. wrote: 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? upper bounds are not larger than Integer.MAX_VALUE, and any negative value in unsigned arithmetic is larger. I love this hack. 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 - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: harmony-dev- [EMAIL PROTECTED] - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- Egor Pasko, Intel Managed Runtime Division - Terms of use : http://incubator.apache.org/harmony/mailing.html To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
