DNER structs that are not of enregisterable size before lowering

Author: jakobbotsch

src/coreclr/jit/compiler.h

@@ -4194,7 +4194,7 @@ class Compiler
     bool lvaVarDoNotEnregister(unsigned varNum);
 
     void lvSetMinOptsDoNotEnreg();
-    void lvSetEHVarsDoNotEnreg();
+    void lvSetVarsDoNotEnreg();
 
     bool lvaEnregEHVars;
     bool lvaEnregMultiRegVars;

src/coreclr/jit/lclvars.cpp

@@ -1339,11 +1339,11 @@ void Compiler::lvSetMinOptsDoNotEnreg()
 }
 
 //------------------------------------------------------------------------
-// lvSetEHVarsDoNotEnreg:
-//   Set locals that we expect to not be enregisterable due to EH as DNER, to
-//   allow specific optimizations for these by lowering.
+// lvSetVarsDoNotEnreg:
+//   Set locals that we expect to not be enregisterable as DNER, to allow
+//   specific optimizations for these by lowering.
 //
-void Compiler::lvSetEHVarsDoNotEnreg()
+void Compiler::lvSetVarsDoNotEnreg()
 {
     for (unsigned lclNum = 0; lclNum < lvaCount; lclNum++)
     {
@@ -1357,6 +1357,10 @@ void Compiler::lvSetEHVarsDoNotEnreg()
         {
             lvaSetVarDoNotEnregister(lclNum DEBUGARG(DoNotEnregisterReason::LiveInOutOfHandler));
         }
+        else if (varTypeIsStruct(dsc) && !dsc->lvPromoted && !dsc->IsEnregisterableType())
+        {
+            lvaSetVarDoNotEnregister(lclNum DEBUGARG(DoNotEnregisterReason::NotRegSizeStruct));
+        }
     }
 }
 

src/coreclr/jit/lower.cpp

@@ -8930,9 +8930,9 @@ PhaseStatus Lowering::DoPhase()
     }
     else
     {
-        // By this point tracked locals live into EH clauses are _very_ likely to not be enregistered.
-        // DNER this for the same reason above, so that we can contain these locals.
-        m_compiler->lvSetEHVarsDoNotEnreg();
+        // For many locals we know at this point that we won't enregister them,
+        // so DNER these for the same reasons as above.
+        m_compiler->lvSetVarsDoNotEnreg();
     }
 
     if (m_compiler->opts.OptimizationEnabled() && !m_compiler->opts.IsOSR())