AMDGPU/SI: Don't allow unaligned scratch access

Summary: The hardware doesn't support this.

Reviewers: arsenm

Subscribers: kzhuravl, wdng, nhaehnle, yaxunl, llvm-commits, tony-tye

Differential Revision: https://reviews.llvm.org/D25523

llvm-svn: 284257
diff --git a/llvm/lib/Target/AMDGPU/AMDGPU.td b/llvm/lib/Target/AMDGPU/AMDGPU.td
index e0bde33..5f7033e 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPU.td
+++ b/llvm/lib/Target/AMDGPU/AMDGPU.td
@@ -67,6 +67,12 @@
   "Support unaligned global loads and stores"
 >;
 
+def FeatureUnalignedScratchAccess : SubtargetFeature<"unaligned-scratch-access",
+  "UnalignedScratchAccess",
+  "true",
+  "Support unaligned scratch loads and stores"
+>;
+
 def FeatureXNACK : SubtargetFeature<"xnack",
   "EnableXNACK",
   "true",