> But on zEC12 LA works pretty much the same as on z13/z14, it is > indeed not cracked, but still a 2-cycle instruction when using > an index register. So I guess the change really should apply > to zEC12 as well, and this could be as simple as changing the > above line to: > > if (addr.indx && s390_tune >= PROCESSOR_2817_Z196) > > (Note that "addr.base && addr.indx" is the same as just checking > for addr.indx, since s390_decompose_address will never fill in > *just* an index.)
Good point, I adapted the patch and changed the comment. Regards Robin -- gcc/ChangeLog: 2018-07-16 Robin Dapp <rd...@linux.ibm.com> * config/s390/s390.c (preferred_la_operand_p): Do not use LA with index register on z196 or later.
diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c index 23c3f3db621..d8b47c6fe67 100644 --- a/gcc/config/s390/s390.c +++ b/gcc/config/s390/s390.c @@ -4623,11 +4623,11 @@ preferred_la_operand_p (rtx op1, rtx op2) if (addr.indx && !REGNO_OK_FOR_INDEX_P (REGNO (addr.indx))) return false; - /* Avoid LA instructions with index register on z196; it is - preferable to use regular add instructions when possible. - Starting with zEC12 the la with index register is "uncracked" - again. */ - if (addr.indx && s390_tune == PROCESSOR_2817_Z196) + /* Avoid LA instructions with index (and base) register on z196 or + later; it is preferable to use regular add instructions when + possible. Starting with zEC12 the la with index register is + "uncracked" again but still slower than a regular add. */ + if (addr.indx && s390_tune >= PROCESSOR_2817_Z196) return false; if (!TARGET_64BIT && !addr.pointer)