Use TryGetRangeFromAssertions to fold more relops in global assert prop (#112824)

Author: EgorBo

src/coreclr/jit/assertionprop.cpp

@@ -4611,6 +4611,32 @@ GenTree* Compiler::optAssertionPropGlobal_RelOp(ASSERT_VALARG_TP assertions,
         return optAssertionProp_Update(newTree, tree, stmt);
     }
 
+    ValueNum op1VN = vnStore->VNConservativeNormalValue(op1->gtVNPair);
+    ValueNum op2VN = vnStore->VNConservativeNormalValue(op2->gtVNPair);
+
+    // See if we can fold "X relop CNS" using TryGetRangeFromAssertions.
+    int op2cns;
+    if (op1->TypeIs(TYP_INT) && op2->TypeIs(TYP_INT) &&
+        vnStore->IsVNIntegralConstant(op2VN, &op2cns)
+        // "op2cns != 0" is purely a TP quirk (such relops are handled by the code above):
+        && (op2cns != 0))
+    {
+        // NOTE: we can call TryGetRangeFromAssertions for op2 as well if we want, but it's not cheap.
+        Range rng1 = Range(Limit(Limit::keUndef));
+        Range rng2 = Range(Limit(Limit::keConstant, op2cns));
+
+        if (RangeCheck::TryGetRangeFromAssertions(this, op1VN, assertions, &rng1))
+        {
+            RangeOps::RelationKind kind = RangeOps::EvalRelop(tree->OperGet(), tree->IsUnsigned(), rng1, rng2);
+            if ((kind != RangeOps::RelationKind::Unknown))
+            {
+                newTree = kind == RangeOps::RelationKind::AlwaysTrue ? gtNewTrue() : gtNewFalse();
+                newTree = gtWrapWithSideEffects(newTree, tree, GTF_ALL_EFFECT);
+                return optAssertionProp_Update(newTree, tree, stmt);
+            }
+        }
+    }
+
     // Else check if we have an equality check involving a local or an indir
     if (!tree->OperIs(GT_EQ, GT_NE))
     {

src/coreclr/jit/rangecheck.cpp

@@ -801,6 +801,20 @@ void RangeCheck::MergeEdgeAssertions(Compiler*        comp,
                 cmpOper    = GT_LT;
                 limit      = Limit(Limit::keBinOpArray, lenVN, 0);
             }
+            else if ((normalLclVN == lenVN) && comp->vnStore->IsVNInt32Constant(indexVN))
+            {
+                // We have "Const < arr.Length" assertion, it means that "arr.Length >= Const"
+                int indexCns = comp->vnStore->GetConstantInt32(indexVN);
+                if (indexCns >= 0)
+                {
+                    cmpOper = GT_GE;
+                    limit   = Limit(Limit::keConstant, indexCns);
+                }
+                else
+                {
+                    continue;
+                }
+            }
             else
             {
                 continue;
@@ -977,6 +991,11 @@ void RangeCheck::MergeEdgeAssertions(Compiler*        comp,
                 if (!isUnsigned)
                 {
                     pRange->lLimit = limit;
+                    // INT32_MAX as the upper limit is better than UNKNOWN for a constant lower limit.
+                    if (limit.IsConstant() && pRange->UpperLimit().IsUnknown())
+                    {
+                        pRange->uLimit = Limit(Limit::keConstant, INT32_MAX);
+                    }
                 }
                 break;
 

src/coreclr/jit/rangecheck.h

@@ -585,6 +585,89 @@ struct RangeOps
         result.uLimit = Limit(Limit::keConstant, -lo);
         return result;
     }
+
+    enum class RelationKind
+    {
+        AlwaysTrue,
+        AlwaysFalse,
+        Unknown
+    };
+
+    //------------------------------------------------------------------------
+    // EvalRelop: Evaluate the relation between two ranges for the given relop
+    //    Example: "x >= y" is AlwaysTrue when "x.LowerLimit() >= y.UpperLimit()"
+    //
+    // Arguments:
+    //    relop      - The relational operator (LE,LT,GE,GT,EQ,NE)
+    //    isUnsigned - True if the comparison is unsigned
+    //    x          - The left range
+    //    y          - The right range
+    //
+    // Returns:
+    //    AlwaysTrue when the given relop always evaluates to true for the given ranges
+    //    AlwaysFalse when the given relop always evaluates to false for the given ranges
+    //    Otherwise Unknown
+    //
+    static RelationKind EvalRelop(const genTreeOps relop, bool isUnsigned, const Range& x, const Range& y)
+    {
+        const Limit& xLower = x.LowerLimit();
+        const Limit& yLower = y.LowerLimit();
+        const Limit& xUpper = x.UpperLimit();
+        const Limit& yUpper = y.UpperLimit();
+
+        // For unsigned comparisons, we only support non-negative ranges.
+        if (isUnsigned)
+        {
+            if (!xLower.IsConstant() || !yUpper.IsConstant() || (xLower.GetConstant() < 0) ||
+                (yLower.GetConstant() < 0))
+            {
+                return RelationKind::Unknown;
+            }
+        }
+
+        switch (relop)
+        {
+            case GT_GE:
+            case GT_LT:
+                if (xLower.IsConstant() && yUpper.IsConstant() && (xLower.GetConstant() >= yUpper.GetConstant()))
+                {
+                    return relop == GT_GE ? RelationKind::AlwaysTrue : RelationKind::AlwaysFalse;
+                }
+
+                if (xUpper.IsConstant() && yLower.IsConstant() && (xUpper.GetConstant() < yLower.GetConstant()))
+                {
+                    return relop == GT_GE ? RelationKind::AlwaysFalse : RelationKind::AlwaysTrue;
+                }
+                break;
+
+            case GT_GT:
+            case GT_LE:
+                if (xLower.IsConstant() && yUpper.IsConstant() && (xLower.GetConstant() > yUpper.GetConstant()))
+                {
+                    return relop == GT_GT ? RelationKind::AlwaysTrue : RelationKind::AlwaysFalse;
+                }
+
+                if (xUpper.IsConstant() && yLower.IsConstant() && (xUpper.GetConstant() <= yLower.GetConstant()))
+                {
+                    return relop == GT_GT ? RelationKind::AlwaysFalse : RelationKind::AlwaysTrue;
+                }
+                break;
+
+            case GT_EQ:
+            case GT_NE:
+                if ((xLower.IsConstant() && yUpper.IsConstant() && (xLower.GetConstant() > yUpper.GetConstant())) ||
+                    (xUpper.IsConstant() && yLower.IsConstant() && (xUpper.GetConstant() < yLower.GetConstant())))
+                {
+                    return relop == GT_EQ ? RelationKind::AlwaysFalse : RelationKind::AlwaysTrue;
+                }
+                break;
+
+            default:
+                assert(!"unknown comparison operator");
+                break;
+        }
+        return RelationKind::Unknown;
+    }
 };
 
 class RangeCheck