Optimization for full range checks (#70145)

src/coreclr/jit/morph.cpp

@@ -10790,6 +10790,52 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac)
                         }
                     }
                 }
+
+                if (op1->OperIs(GT_LT, GT_GT))
+                {
+                    bool     fold  = false;
+                    GenTree* lNode = op1->gtGetOp1();
+                    GenTree* rNode = op1->gtGetOp2();
+
+#if defined(HOST_X86) || defined(HOST_ARM)
+                    ssize_t longMin = INT32_MIN;
+                    ssize_t longMax = INT32_MAX;
+#else
+                    ssize_t longMin     = INT64_MIN;
+                    ssize_t longMax     = INT64_MAX;
+#endif
+                    if (op1->OperIs(GT_LT))
+                    {
+                        // Folds:
+                        // 1. byte x >= 0 => true
+                        // 2. int  x >= int.MinValue => true
+                        // 3. long x >= long.MaxValue => true
+
+                        fold = (lNode->TypeIs(TYP_UBYTE) && rNode->IsIntegralConst(0)) ||
+                               (lNode->TypeIs(TYP_INT) && rNode->IsIntegralConst(INT32_MIN)) ||
+                               (lNode->TypeIs(TYP_LONG) && rNode->IsIntegralConst(longMin));
+                    }
+
+                    if (op1->OperIs(GT_GT))
+                    {
+                        // Folds:
+                        // 1. byte x <= byte.MaxValue => true
+                        // 2. int  x <= int.MaxValue => true
+                        // 3. long x <= long.MaxValue => true
+
+                        fold = (lNode->TypeIs(TYP_UBYTE) && rNode->IsIntegralConst(BYTE_MAX)) ||
+                               (lNode->TypeIs(TYP_INT) && rNode->IsIntegralConst(INT32_MAX)) ||
+                               (lNode->TypeIs(TYP_LONG) && rNode->IsIntegralConst(longMax));
+                    }
+
+                    if (fold)
+                    {
+                        GenTree* ret = gtNewIconNode(1, TYP_INT);
+                        ret->SetVNsFromNode(tree);
+                        DEBUG_DESTROY_NODE(tree);
+                        return fgMorphTree(ret);
+                    }
+                }
             }
         }
 
@@ -13025,7 +13071,7 @@ GenTree* Compiler::fgOptimizeMultiply(GenTreeOp* mul)
         // Should we try to replace integer multiplication with lea/add/shift sequences?
         bool mulShiftOpt = compCodeOpt() != SMALL_CODE;
 #else  // !TARGET_XARCH
-        bool mulShiftOpt = false;
+        bool                mulShiftOpt = false;
 #endif // !TARGET_XARCH
 
         size_t abs_mult      = (mult >= 0) ? mult : -mult;