AMDGPU/GlobalISel: Select flat loads

Now that the patterns use the new PatFrag address space support, the
only blocker to importing most load patterns is the addressing mode
complex patterns.

llvm-svn: 366237
diff --git a/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp b/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
index 3cf4fbc..670f622 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
@@ -497,6 +497,9 @@
       .custom();
   }
 
+  // TODO: Should load to s16 be legal? Most loads extend to 32-bits, but we
+  // handle some operations by just promoting the register during
+  // selection. There are also d16 loads on GFX9+ which preserve the high bits.
   getActionDefinitionsBuilder({G_LOAD, G_STORE})
     .narrowScalarIf([](const LegalityQuery &Query) {
         unsigned Size = Query.Types[0].getSizeInBits();