This patch changes the PowerPC backend to generate VSX load/store instructions
for all vector loads/stores on Power8 and earlier (LE) instead of VMX
load/store instructions. The reason for this change is because VMX instructions
require the vector to be 16-byte aligned. So, a vector load/store will fail with
VMX instructions if the vector is misaligned. Also, `gcc` generates VSX
instructions in this situation which allow for unaligned access but require a
swap instruction after loading/before storing. This is not an issue for BE
because we already emit VSX instructions since no swap is required. And this is
not an issue on Power9 and up since we have access to `lxv[x]`/`stxv[x]` which
allow for unaligned access and do not require swaps.
This patch also delays the VSX load/store for LE combines until after
LegalizeOps to prioritize other load/store combines.
Reviewed By: #powerpc, stefanp
Differential Revision: https://reviews.llvm.org/D127309
This patch includes the following updates to the load/store refactoring effort introduced in D93370:
- Update various VSX patterns that use to "force" an XForm, to instead just XForm.
This allows the ability for the patterns to compute the most optimal addressing
mode (and to produce a DForm instruction when possible)
- Update pattern and test case for the LXVD2X/STXVD2X intrinsics
- Update LIT test cases that use to use the XForm instruction to use the DForm instruction
Differential Revision: https://reviews.llvm.org/D95115
tryLatency compares two sched candidates. For the top zone it prefers
the one with lesser depth, but only if that depth is greater than the
total latency of the instructions we've already scheduled -- otherwise
its latency would be hidden and there would be no stall.
Unfortunately it only tests the depth of one of the candidates. This can
lead to situations where the TopDepthReduce heuristic does not kick in,
but a lower priority heuristic chooses the other candidate, whose depth
*is* greater than the already scheduled latency, which causes a stall.
The fix is to apply the heuristic if the depth of *either* candidate is
greater than the already scheduled latency.
All this also applies to the BotHeightReduce heuristic in the bottom
zone.
Differential Revision: https://reviews.llvm.org/D72392
PowerPC has instruction to do the semantics of this piece of code:
vector int foo(vector int m, vector int n) {
return (m + n + 1) >> 1;
}
This patch is adding the match rule to select it.
Differential Revision: https://reviews.llvm.org/D71002
