C#: Support for unsigned shift right in the experimental intermediate representation.

Author: michaelnebel

csharp/ql/src/experimental/ir/implementation/Opcode.qll

@@ -30,6 +30,7 @@ private newtype TOpcode =
   TNegate() or
   TShiftLeft() or
   TShiftRight() or
+  TUnsignedShiftRight() or
   TBitAnd() or
   TBitOr() or
   TBitXor() or
@@ -652,6 +653,15 @@ module Opcode {
     final override string toString() { result = "ShiftRight" }
   }
 
+  /**
+   * The `Opcode` for a `UnsignedShiftRightInstruction`.
+   *
+   * See the `UnsignedShiftRightInstruction` documentation for more details.
+   */
+  class UnsignedShiftRight extends BinaryBitwiseOpcode, TUnsignedShiftRight {
+    final override string toString() { result = "UnsignedShiftRight" }
+  }
+
   /**
    * The `Opcode` for a `BitAndInstruction`.
    *

csharp/ql/src/experimental/ir/implementation/raw/Instruction.qll

@@ -1204,6 +1204,17 @@ class ShiftRightInstruction extends BinaryBitwiseInstruction {
   ShiftRightInstruction() { this.getOpcode() instanceof Opcode::ShiftRight }
 }
 
+/**
+ * An instruction that shifts its left operand to the right by the number of bits specified by its
+ * right operand.
+ *
+ * Both operands must have an integer type. The result has the same type as the left operand.
+ * The leftmost bits are zero-filled.
+ */
+class UnsignedShiftRightInstruction extends BinaryBitwiseInstruction {
+  UnsignedShiftRightInstruction() { this.getOpcode() instanceof Opcode::UnsignedShiftRight }
+}
+
 /**
  * An instruction that performs a binary arithmetic operation involving at least one pointer
  * operand.

csharp/ql/src/experimental/ir/implementation/raw/internal/TranslatedExpr.qll

@@ -1095,6 +1095,8 @@ private Opcode binaryBitwiseOpcode(BinaryBitwiseOperation expr) {
   or
   expr instanceof RightShiftExpr and result instanceof Opcode::ShiftRight
   or
+  expr instanceof UnsignedRightShiftExpr and result instanceof Opcode::UnsignedShiftRight
+  or
   expr instanceof BitwiseAndExpr and result instanceof Opcode::BitAnd
   or
   expr instanceof BitwiseOrExpr and result instanceof Opcode::BitOr
@@ -1378,7 +1380,8 @@ class TranslatedAssignOperation extends TranslatedAssignment {
   private Type getConvertedLeftOperandType() {
     if
       expr instanceof AssignLeftShiftExpr or
-      expr instanceof AssignRightShiftExpr
+      expr instanceof AssignRightShiftExpr or
+      expr instanceof AssignUnsighedRightShiftExpr
     then result = this.getLeftOperand().getResultType()
     else
       // The right operand has already been converted to the type of the op.
@@ -1419,6 +1422,8 @@ class TranslatedAssignOperation extends TranslatedAssignment {
     expr instanceof AssignLeftShiftExpr and result instanceof Opcode::ShiftLeft
     or
     expr instanceof AssignRightShiftExpr and result instanceof Opcode::ShiftRight
+    or
+    expr instanceof AssignUnsighedRightShiftExpr and result instanceof Opcode::UnsignedShiftRight
   }
 
   override predicate hasInstruction(Opcode opcode, InstructionTag tag, CSharpType resultType) {

csharp/ql/src/experimental/ir/implementation/unaliased_ssa/Instruction.qll

@@ -1204,6 +1204,17 @@ class ShiftRightInstruction extends BinaryBitwiseInstruction {
   ShiftRightInstruction() { this.getOpcode() instanceof Opcode::ShiftRight }
 }
 
+/**
+ * An instruction that shifts its left operand to the right by the number of bits specified by its
+ * right operand.
+ *
+ * Both operands must have an integer type. The result has the same type as the left operand.
+ * The leftmost bits are zero-filled.
+ */
+class UnsignedShiftRightInstruction extends BinaryBitwiseInstruction {
+  UnsignedShiftRightInstruction() { this.getOpcode() instanceof Opcode::UnsignedShiftRight }
+}
+
 /**
  * An instruction that performs a binary arithmetic operation involving at least one pointer
  * operand.

csharp/ql/src/experimental/ir/rangeanalysis/SignAnalysis.qll

@@ -522,6 +522,8 @@ module SignAnalysisCached {
         i instanceof ShiftRightInstruction and
         not i.getResultType().(IntegralType) instanceof SignedIntegralType and
         result = s1.urshift(s2)
+        or
+        i instanceof UnsignedShiftRightInstruction and result = s1.urshift(s2)
       )
       or
       // use hasGuard here?