LI76635: INEFFICIENT REGISTER MOVE USING XVCPSGND
Fixes are available
Closed as program error.
When analyzing listing files that contain "xvcpsgnd" instructions, the compiler should be generating more efficient code for the that instruction. Compiler uses register moves xvcpsgndp. But instead, it can make use of the xxlor and xxpermdi instructions. xxlor only takes 2c (can run only on pipe 0). xxpermdi takes 3c (can run only on pipe 1). xvcpsgnd always takes 7c and can run on both pipes. ==> A register move with with xxlor is much faster. ==> 2 register moves can be implemented with xxlor + xxpermdi Moving a register pair can be required for duplicating _Decimal128 values. So, the following instructions: 1435| 000044 xvcpsgnd F0021780 1 LRVS vs0=vs2 1435| 000048 xvcpsgnd F0231F80 1 LRVS vs1=vs3 can be replaced with: xxlor vs0,vs2,vs2 xxpermdi vs1,vs3,vs3,0
Users Affected: Users who use _Decimal128 values which internally makes use of xvcpsgnd can be potentially affected by this issue. Problem Description: The compiler inefficiently creates xvcpsgnd instructions which can potentially be replaced with xxlor and xxpermdi instructions. However, this is not always the case, as it depends on which architecture the final exe is being executed on.
Replacing xvcpsgnd with xxlor and xxpermdi is beneficial on PWR7. As a result, the compiler will now recognize such circumstances under the -qtune=pwr7 option and will replace xvcpsgnd with xxlor and xxpermdi.
Reported component name
XL C/C++ FOR LI
Reported component ID
NoSpecatt / Xsystem
Last modified date
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fixed component name
XL C/C++ FOR LI
Fixed component ID
Applicable component levels
RB10 PSN IV12845