[JIT] [Issue: 61620] Optimizing ARM64 for *x = dblCns; (#61847)

* [Issue: 61620] Optimizing ARM64 for *x = 0;

* Update src/coreclr/jit/lower.cpp

Co-authored-by: SingleAccretion <[email protected]>

* Fixed bug with * x = dConst if dConst is not 0

* remove extra printf

* Replacing IsFPZero with IsCnsNonZeroFltOrDbl for STOREIND Minor edits with conditional compilation in lower.cpp

* fixed ARM codegen for STOREIND

* Update src/coreclr/jit/lower.cpp

Co-authored-by: SingleAccretion <[email protected]>

* Update src/coreclr/jit/lower.cpp

Co-authored-by: SingleAccretion <[email protected]>

* fix formatting

Co-authored-by: SingleAccretion <[email protected]>

Author: SeanWoo

src/coreclr/jit/lower.cpp

@@ -6783,6 +6783,51 @@ void Lowering::LowerStoreIndirCommon(GenTreeStoreInd* ind)
     TryCreateAddrMode(ind->Addr(), true, ind->TypeGet());
     if (!comp->codeGen->gcInfo.gcIsWriteBarrierStoreIndNode(ind))
     {
+        if (varTypeIsFloating(ind) && ind->Data()->IsCnsFltOrDbl())
+        {
+            // Optimize *x = DCON to *x = ICON which can be slightly faster and/or smaller.
+            GenTree*  data   = ind->Data();
+            double    dblCns = data->AsDblCon()->gtDconVal;
+            ssize_t   intCns = 0;
+            var_types type   = TYP_UNKNOWN;
+            // XARCH: we can always contain the immediates.
+            // ARM64: zero can always be contained, other cases will use immediates from the data
+            //        section and it is not a clear win to switch them to inline integers.
+            // ARM:   FP constants are assembled from integral ones, so it is always profitable
+            //        to directly use the integers as it avoids the int -> float conversion.
+            CLANG_FORMAT_COMMENT_ANCHOR;
+
+#if defined(TARGET_XARCH) || defined(TARGET_ARM)
+            bool shouldSwitchToInteger = true;
+#else // TARGET_ARM64
+            bool shouldSwitchToInteger = !data->IsCnsNonZeroFltOrDbl();
+#endif
+
+            if (shouldSwitchToInteger)
+            {
+                if (ind->TypeIs(TYP_FLOAT))
+                {
+                    float fltCns = static_cast<float>(dblCns); // should be a safe round-trip
+                    intCns       = static_cast<ssize_t>(*reinterpret_cast<INT32*>(&fltCns));
+                    type         = TYP_INT;
+                }
+#ifdef TARGET_64BIT
+                else
+                {
+                    assert(ind->TypeIs(TYP_DOUBLE));
+                    intCns = static_cast<ssize_t>(*reinterpret_cast<INT64*>(&dblCns));
+                    type   = TYP_LONG;
+                }
+#endif
+            }
+
+            if (type != TYP_UNKNOWN)
+            {
+                data->BashToConst(intCns, type);
+                ind->ChangeType(type);
+            }
+        }
+
         LowerStoreIndir(ind);
     }
 }
@@ -6852,7 +6897,7 @@ void Lowering::TransformUnusedIndirection(GenTreeIndir* ind, Compiler* comp, Bas
 #ifdef TARGET_ARM64
     bool useNullCheck = true;
 #elif TARGET_ARM
-    bool useNullCheck = false;
+    bool         useNullCheck          = false;
 #else  // TARGET_XARCH
     bool useNullCheck = !ind->Addr()->isContained();
 #endif // !TARGET_XARCH

src/coreclr/jit/lowerxarch.cpp

@@ -129,36 +129,6 @@ void Lowering::LowerStoreIndir(GenTreeStoreInd* node)
             return;
         }
     }
-    else if (node->Data()->IsCnsFltOrDbl())
-    {
-        // Optimize *x = DCON to *x = ICON which is slightly faster on xarch
-        GenTree*  data   = node->Data();
-        double    dblCns = data->AsDblCon()->gtDconVal;
-        ssize_t   intCns = 0;
-        var_types type   = TYP_UNKNOWN;
-
-        if (node->TypeIs(TYP_FLOAT))
-        {
-            float fltCns = static_cast<float>(dblCns); // should be a safe round-trip
-            intCns       = static_cast<ssize_t>(*reinterpret_cast<INT32*>(&fltCns));
-            type         = TYP_INT;
-        }
-#ifdef TARGET_AMD64
-        else
-        {
-            assert(node->TypeIs(TYP_DOUBLE));
-            intCns = static_cast<ssize_t>(*reinterpret_cast<INT64*>(&dblCns));
-            type   = TYP_LONG;
-        }
-#endif
-
-        if (type != TYP_UNKNOWN)
-        {
-            data->SetContained();
-            data->BashToConst(intCns, type);
-            node->ChangeType(type);
-        }
-    }
 
     // Optimization: do not unnecessarily zero-extend the result of setcc.
     if (varTypeIsByte(node) && (node->Data()->OperIsCompare() || node->Data()->OperIs(GT_SETCC)))