AMDGPU: Add D16 instructions preserve unused bits feature

- Predicate D16 patterns on this new feature
- Added this new feature to gfx900/2/4

Differential Revision: https://reviews.llvm.org/D46366

llvm-svn: 331551
diff --git a/llvm/lib/Target/AMDGPU/BUFInstructions.td b/llvm/lib/Target/AMDGPU/BUFInstructions.td
index dc528fb..999d553 100644
--- a/llvm/lib/Target/AMDGPU/BUFInstructions.td
+++ b/llvm/lib/Target/AMDGPU/BUFInstructions.td
@@ -1374,7 +1374,7 @@
 defm : MUBUFScratchLoadPat <BUFFER_LOAD_DWORDX2_OFFEN, BUFFER_LOAD_DWORDX2_OFFSET, v2i32, load_private>;
 defm : MUBUFScratchLoadPat <BUFFER_LOAD_DWORDX4_OFFEN, BUFFER_LOAD_DWORDX4_OFFSET, v4i32, load_private>;
 
-let OtherPredicates = [HasD16LoadStore] in {
+let OtherPredicates = [D16PreservesUnusedBits] in {
 defm : MUBUFScratchLoadPat_Hi16<BUFFER_LOAD_SHORT_D16_HI_OFFEN, BUFFER_LOAD_SHORT_D16_HI_OFFSET, i16, load_private>;
 defm : MUBUFScratchLoadPat_Hi16<BUFFER_LOAD_UBYTE_D16_HI_OFFEN, BUFFER_LOAD_UBYTE_D16_HI_OFFSET, i16, az_extloadi8_private>;
 defm : MUBUFScratchLoadPat_Hi16<BUFFER_LOAD_SBYTE_D16_HI_OFFEN, BUFFER_LOAD_SBYTE_D16_HI_OFFSET, i16, sextloadi8_private>;
@@ -1489,7 +1489,7 @@
 defm : MUBUFScratchStorePat <BUFFER_STORE_DWORDX4_OFFEN, BUFFER_STORE_DWORDX4_OFFSET, v4i32, store_private>;
 
 
-let OtherPredicates = [HasD16LoadStore] in {
+let OtherPredicates = [D16PreservesUnusedBits] in {
  // Hiding the extract high pattern in the PatFrag seems to not
  // automatically increase the complexity.
 let AddedComplexity = 1 in {