[ARM] Split large truncating MVE stores

MVE does not have a simple sign extend instruction that can move elements
across lanes. We currently often end up moving each lane into and out of a GPR,
in order to get elements into the correct places. When we have a store of a
trunc (or a extend of a load), we can instead just split the store/load in two,
using the narrowing/widening load/store instructions from each half of the
vector.

This does that for stores. It happens very early in a store combine, so as to
easily detect the truncates. (It would be possible to do this later, but that
would involve looking through a buildvector of extract elements. Not impossible
but this way seemed simpler).

By enabling store combines we also get a vmovdrr combine for free, helping some
other tests.

Differential Revision: https://reviews.llvm.org/D67828

llvm-svn: 372717

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/test/CodeGen/Thumb2/float-ops.ll b/llvm/test/CodeGen/Thumb2/float-ops.ll
index cbd8ca557a0..cc3684c2ec0 100644
--- a/llvm/test/CodeGen/Thumb2/float-ops.ll
+++ b/llvm/test/CodeGen/Thumb2/float-ops.ll
@@ -130,7 +130,7 @@ define void @store_d(double* %a, double %b) {
 entry:
 ; CHECK-LABEL: store_d:
 ; NOREGS: strd r2, r3, [r0]
-; ONLYREGS: vstr d0, [r0]
+; ONLYREGS: strd r2, r3, [r0]
 ; HARD: vstr d0, [r0]
   store double %b, double* %a, align 8
   ret void