JIT: reduce importer spilling for some stfld (dotnet#51158)

If we know which local is going to be updated, just spill that local.
BruceForstall · Apr 14, 2021 · 6d098da · 6d098da
1 parent 5f95440
commit 6d098da
Showing 1 changed file with 10 additions and 1 deletion.
diff --git a/src/coreclr/jit/importer.cpp b/src/coreclr/jit/importer.cpp
@@ -15178,7 +15178,16 @@ void Compiler::impImportBlockCode(BasicBlock* block)
                 {
                     assert(tiObj);
 
-                    if (impIsValueType(tiObj))
+                    // If we can resolve the field to be within some local,
+                    // then just spill that local.
+                    //
+                    GenTreeLclVarCommon* const lcl = obj->IsLocalAddrExpr();
+
+                    if (lcl != nullptr)
+                    {
+                        impSpillLclRefs(lcl->GetLclNum());
+                    }
+                    else if (impIsValueType(tiObj))
                     {
                         impSpillEvalStack();
                     }