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
There are two reasons this shouldn't be restricted to Power8 and up:
1. For XL compatibility
2. Because clang will expand comparison operators to these intrinsics*
*Without this patch, the following causes a selection error:
int test(vector signed long a, vector signed long b) {
return a < b;
}
This patch provides the handling for the intrinsics in the back
end and removes the Power8 guards from the predicate functions
(vec_{all|any}_{eq|ne|gt|ge|lt|le}).
