[RyuJIT] static readonly fields can be Invariant (#44562)

Co-authored-by: Andy Ayers <andya@microsoft.com>
dotnet · Mar 2, 2021 · 94e163a · 94e163a
1 parent c003837
commit 94e163a
Showing 1 changed file with 19 additions and 1 deletion.
diff --git a/src/coreclr/jit/morph.cpp b/src/coreclr/jit/morph.cpp
@@ -6490,7 +6490,17 @@ GenTree* Compiler::fgMorphField(GenTree* tree, MorphAddrContext* mac)
             assert(pFldAddr == nullptr);
 
 #ifdef TARGET_64BIT
-            if (IMAGE_REL_BASED_REL32 != eeGetRelocTypeHint(fldAddr))
+            bool isStaticReadOnlyInited = false;
+            bool plsSpeculative         = true;
+            if (info.compCompHnd->getStaticFieldCurrentClass(symHnd, &plsSpeculative) != NO_CLASS_HANDLE)
+            {
+                isStaticReadOnlyInited = !plsSpeculative;
+            }
+
+            // even if RelocTypeHint is REL32 let's still prefer IND over GT_CLS_VAR
+            // for static readonly fields of statically initialized classes - thus we can
+            // apply GTF_IND_INVARIANT flag and make it hoistable/CSE-friendly
+            if (isStaticReadOnlyInited || (IMAGE_REL_BASED_REL32 != eeGetRelocTypeHint(fldAddr)))
             {
                 // The address is not directly addressible, so force it into a
                 // constant, so we handle it properly
@@ -6510,6 +6520,14 @@ GenTree* Compiler::fgMorphField(GenTree* tree, MorphAddrContext* mac)
                 tree->SetOper(GT_IND);
                 tree->AsOp()->gtOp1 = addr;
 
+                if (isStaticReadOnlyInited)
+                {
+                    JITDUMP("Marking initialized static read-only field '%s' as invariant.\n", eeGetFieldName(symHnd));
+                    tree->gtFlags |= GTF_IND_INVARIANT;
+                    tree->gtFlags &= ~GTF_ICON_INITCLASS;
+                    addr->gtFlags = GTF_ICON_CONST_PTR;
+                }
+
                 return fgMorphSmpOp(tree);
             }
             else