Re: [PATCH 01/22] target/i386: optimize computation of JL and JLE from flags

2023-12-28 Thread Richard Henderson
On 12/23/23 05:15, Paolo Bonzini wrote: Take advantage of the fact that there can be no 1 bits between SF and OF. If they were adjacent, you could sum SF and get a carry only if SF was already set. Then the value of OF in the sum is the XOR of OF itself, the carry (which is SF) and 0 (the value

[PATCH 01/22] target/i386: optimize computation of JL and JLE from flags

2023-12-22 Thread Paolo Bonzini
Take advantage of the fact that there can be no 1 bits between SF and OF. If they were adjacent, you could sum SF and get a carry only if SF was already set. Then the value of OF in the sum is the XOR of OF itself, the carry (which is SF) and 0 (the value of the OF bit in the addend): this is