clang/AMDGPU: Emit grid size builtins with range metadata

These cannot be 0.

Author: arsenm

clang/lib/CodeGen/CGBuiltin.cpp

@@ -18671,6 +18671,12 @@ Value *EmitAMDGPUGridSize(CodeGenFunction &CGF, unsigned Index) {
   auto *GEP = CGF.Builder.CreateGEP(CGF.Int8Ty, DP, Offset);
   auto *LD = CGF.Builder.CreateLoad(
       Address(GEP, CGF.Int32Ty, CharUnits::fromQuantity(4)));
+
+  llvm::MDBuilder MDB(CGF.getLLVMContext());
+
+  // Known non-zero.
+  LD->setMetadata(llvm::LLVMContext::MD_range,
+                  MDB.createRange(APInt(32, 1), APInt::getZero(32)));
   LD->setMetadata(llvm::LLVMContext::MD_invariant_load,
                   llvm::MDNode::get(CGF.getLLVMContext(), {}));
   return LD;

clang/test/CodeGenOpenCL/builtins-amdgcn.cl

@@ -639,7 +639,7 @@ void test_get_workgroup_size(int d, global int *out)
 // CHECK-LABEL: @test_get_grid_size(
 // CHECK: {{.*}}call align 4 dereferenceable(64){{.*}} ptr addrspace(4) @llvm.amdgcn.dispatch.ptr()
 // CHECK: getelementptr inbounds i8, ptr addrspace(4) %{{.*}}, i64 %{{.+}}
-// CHECK: load i32, ptr addrspace(4) %{{.*}}, align 4, !invariant.load
+// CHECK: load i32, ptr addrspace(4) %{{.*}}, align 4, !range [[$GRID_RANGE:![0-9]+]], !invariant.load
 void test_get_grid_size(int d, global int *out)
 {
 	switch (d) {
@@ -896,5 +896,6 @@ void test_set_fpenv(unsigned long env) {
   __builtin_amdgcn_set_fpenv(env);
 }
 
+// CHECK-DAG: [[$GRID_RANGE]] = !{i32 1, i32 0}
 // CHECK-DAG: [[$WS_RANGE]] = !{i16 1, i16 1025}
 // CHECK-DAG: attributes #[[$NOUNWIND_READONLY]] = { convergent mustprogress nocallback nofree nounwind willreturn memory(none) }