[AMDGPU] set read_only access qualifier for pointers

If a kernel's pointer argument is known to be readonly
set access qualifier accordingly. This allows RT not to
flush caches before dispatches.

Differential Revision: https://reviews.llvm.org/D32091

llvm-svn: 300362

1 files changed, 8 insertions, 3 deletions

diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUCodeObjectMetadataStreamer.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUCodeObjectMetadataStreamer.cpp
index 59571a48a96..29a6ab9fbe9 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUCodeObjectMetadataStreamer.cpp
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUCodeObjectMetadataStreamer.cpp
@@ -478,9 +478,14 @@ void MetadataStreamer::emitKernelArg(const Argument &Arg) {
     BaseTypeName = cast<MDString>(Node->getOperand(ArgNo))->getString();
 
   StringRef AccQual;
-  Node = Func->getMetadata("kernel_arg_access_qual");
-  if (Node && ArgNo < Node->getNumOperands())
-    AccQual = cast<MDString>(Node->getOperand(ArgNo))->getString();
+  if (Arg.getType()->isPointerTy() && Arg.onlyReadsMemory() &&
+      Arg.hasNoAliasAttr()) {
+    AccQual = "read_only";
+  } else {
+    Node = Func->getMetadata("kernel_arg_access_qual");
+    if (Node && ArgNo < Node->getNumOperands())
+      AccQual = cast<MDString>(Node->getOperand(ArgNo))->getString();
+  }
 
   StringRef Name;
   Node = Func->getMetadata("kernel_arg_name");