From: Babu Moger <babu.moger@xxxxxxxxxx> Date: Fri, 17 Mar 2017 14:52:21 -0600 > Avoid un-intended DCTI Couples. Use of DCTI couples is deprecated. > Also address the "Programming Note" for optimal performance. > > Here is the complete text from Oracle SPARC Architecture Specs. > > 6.3.4.7 DCTI Couples > "A delayed control transfer instruction (DCTI) in the delay slot of > another DCTI is referred to as a “DCTI couple”. The use of DCTI couples > is deprecated in the Oracle SPARC Architecture; no new software should > place a DCTI in the delay slot of another DCTI, because on future Oracle > SPARC Architecture implementations DCTI couples may execute either > slowly or differently than the programmer assumes it will. > > SPARC V8 and SPARC V9 Compatibility Note > The SPARC V8 architecture left behavior undefined for a DCTI couple. The > SPARC V9 architecture defined behavior in that case, but as of > UltraSPARC Architecture 2005, use of DCTI couples was deprecated. > Software should not expect high performance from DCTI couples, and > performance of DCTI couples should be expected to decline further in > future processors. > > Programming Note > As noted in TABLE 6-5 on page 115, an annulled branch-always > (branch-always with a = 1) instruction is not architecturally a DCTI. > However, since not all implementations make that distinction, for > optimal performance, a DCTI should not be placed in the instruction word > immediately following an annulled branch-always instruction (BA,A or > BPA,A)." > > Signed-off-by: Babu Moger <babu.moger@xxxxxxxxxx> > Reviewed-by: Rob Gardner <rob.gardner@xxxxxxxxxx> Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
