--- a/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.asm.aarch64/src/org/graalvm/compiler/asm/aarch64/AArch64MacroAssembler.java	Tue Mar 12 12:12:01 2019 -0700
+++ b/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.asm.aarch64/src/org/graalvm/compiler/asm/aarch64/AArch64MacroAssembler.java	Tue Mar 12 19:17:42 2019 +0100
@@ -33,6 +33,9 @@
 import static org.graalvm.compiler.asm.aarch64.AArch64MacroAssembler.AddressGenerationPlan.WorkPlan.ADD_TO_BASE;
 import static org.graalvm.compiler.asm.aarch64.AArch64MacroAssembler.AddressGenerationPlan.WorkPlan.ADD_TO_INDEX;
 import static org.graalvm.compiler.asm.aarch64.AArch64MacroAssembler.AddressGenerationPlan.WorkPlan.NO_WORK;
+
+import org.graalvm.compiler.asm.BranchTargetOutOfBoundsException;
+
 import static jdk.vm.ci.aarch64.AArch64.CPU;
 import static jdk.vm.ci.aarch64.AArch64.r8;
 import static jdk.vm.ci.aarch64.AArch64.r9;
@@ -1452,7 +1455,7 @@
      *
      * @param cmp general purpose register. May not be null, zero-register or stackpointer.
      * @param uimm6 Unsigned 6-bit bit index.
-     * @param label Can only handle 21-bit word-aligned offsets for now. May be unbound. Non null.
+     * @param label Can only handle 16-bit word-aligned offsets for now. May be unbound. Non null.
      */
     public void tbnz(Register cmp, int uimm6, Label label) {
         assert NumUtil.isUnsignedNbit(6, uimm6);
@@ -1472,7 +1475,7 @@
      *
      * @param cmp general purpose register. May not be null, zero-register or stackpointer.
      * @param uimm6 Unsigned 6-bit bit index.
-     * @param label Can only handle 21-bit word-aligned offsets for now. May be unbound. Non null.
+     * @param label Can only handle 16-bit word-aligned offsets for now. May be unbound. Non null.
      */
     public void tbz(Register cmp, int uimm6, Label label) {
         assert NumUtil.isUnsignedNbit(6, uimm6);
@@ -1681,6 +1684,9 @@
                 int sizeEncoding = information & NumUtil.getNbitNumberInt(6);
                 int regEncoding = information >>> 6;
                 Register reg = AArch64.cpuRegisters.get(regEncoding);
+                if (!NumUtil.isSignedNbit(16, branchOffset)) {
+                    throw new BranchTargetOutOfBoundsException(true, "Branch target %d out of bounds", branchOffset);
+                }
                 switch (type) {
                     case BRANCH_BIT_NONZERO:
                         super.tbnz(reg, sizeEncoding, branchOffset, branch);