Correct register pressure calculation in presence of subregs

If a subreg is used in an instruction it counts as a whole superreg
for the purpose of register pressure calculation. This patch corrects
improper register pressure calculation by examining operand's lane mask.

Differential Revision: https://reviews.llvm.org/D29835

llvm-svn: 296009
diff --git a/llvm/test/CodeGen/AMDGPU/load-global-i32.ll b/llvm/test/CodeGen/AMDGPU/load-global-i32.ll
index e333534..b606b25 100644
--- a/llvm/test/CodeGen/AMDGPU/load-global-i32.ll
+++ b/llvm/test/CodeGen/AMDGPU/load-global-i32.ll
@@ -424,25 +424,25 @@
 ; GCN-NOHSA: buffer_store_dwordx4
 ; GCN-NOHSA: buffer_store_dwordx4
 
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
 
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
 
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
 
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
-; GCN-HSA: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
+; GCN-HSA-DAG: flat_store_dwordx4
 
 define void @global_sextload_v32i32_to_v32i64(<32 x i64> addrspace(1)* %out, <32 x i32> addrspace(1)* %in) #0 {
   %ld = load <32 x i32>, <32 x i32> addrspace(1)* %in