[PATCH] D143069: [DAGCombine] Allow DAGCombine to remove dead masked stores

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen added inline comments.


================
Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:11369
+        !MST->getBasePtr().isUndef() &&
+        ((Mask == MST1->getMask() && MST->getMemoryVT().getStoreSize() ==
+                                         MST1->getMemoryVT().getStoreSize()) ||
----------------
> fixed error with the same mask but different type size by forbid to delete the store
I'm not sure if this is the reason you made this change, but the test that previously removed the redundant store:
```define void @dead_masked_store_same_mask_bigger_type(<vscale x 4 x i16> %val, <vscale x 4 x i32> %val1, ptr %a, <vscale x 4 x i1> %mask) {
; CHECK-LABEL: dead_masked_store_same_mask_bigger_type:
; CHECK:       // %bb.0:
; CHECK-NEXT:    st1w { z1.s }, p0, [x0]
; CHECK-NEXT:    ret
  call void @llvm.masked.store.nxv4i16(<vscale x 4 x i16> %val, ptr %a, i32 4, <vscale x 4 x i1> %mask)
  call void @llvm.masked.store.nxv4i32(<vscale x 4 x i32> %val1, ptr %a, i32 4, <vscale x 4 x i1> %mask)
  ret void
}
```
Is now doing this:
```define void @dead_masked_store_same_mask_bigger_type(<vscale x 4 x i16> %val, <vscale x 4 x i32> %val1, ptr %a, <vscale x 4 x i1> %mask) {
; CHECK-LABEL: dead_masked_store_same_mask_bigger_type:
; CHECK:       // %bb.0:
; CHECK-NEXT:    st1h { z0.s }, p0, [x0]
; CHECK-NEXT:    st1w { z1.s }, p0, [x0]
; CHECK-NEXT:    ret
  call void @llvm.masked.store.nxv4i16(<vscale x 4 x i16> %val, ptr %a, i32 4, <vscale x 4 x i1> %mask)
  call void @llvm.masked.store.nxv4i32(<vscale x 4 x i32> %val1, ptr %a, i32 4, <vscale x 4 x i1> %mask)
  ret void
}```

The second store is overwriting **all** the i16 elements that were stored in the first llvm.masked.store, with i32 elements from the second llvm.masked.store, so that means the first store can be removed right?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D143069/new/

https://reviews.llvm.org/D143069