top | item 23353194 (no title) Suncho | 5 years ago > each register's carry bits are independent from the ones that get carries added from the last registerNo they're not. Let's say B's non-carry bits are all 1. If you carry anything from C, that will affect B's carry bits. discuss order hn newest londons_explore|5 years ago You could check if the middle 64-12-12 bits are all 1's, and if they are branch to a slow codepath.It would be an incredibly rare case, so branch prediction will always get it right, and the cost of a branch nearly nill. a1369209993|5 years ago If you're trying to add two 256-bit numbers, there's probably cryptography involved, and data-dependant branches are poison to crypto code.
londons_explore|5 years ago You could check if the middle 64-12-12 bits are all 1's, and if they are branch to a slow codepath.It would be an incredibly rare case, so branch prediction will always get it right, and the cost of a branch nearly nill. a1369209993|5 years ago If you're trying to add two 256-bit numbers, there's probably cryptography involved, and data-dependant branches are poison to crypto code.
a1369209993|5 years ago If you're trying to add two 256-bit numbers, there's probably cryptography involved, and data-dependant branches are poison to crypto code.
londons_explore|5 years ago
It would be an incredibly rare case, so branch prediction will always get it right, and the cost of a branch nearly nill.
a1369209993|5 years ago