Index: lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
===================================================================
--- lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
@@ -2554,6 +2554,8 @@
           Int = 0x142;
         } else if (Int == 31) {
           Int = 0x143;
+        } else {
+          return MatchOperand_ParseFail;
         }
       } else {
         return MatchOperand_ParseFail;
Index: test/MC/AMDGPU/regression/bug28538.s
===================================================================
--- /dev/null
+++ test/MC/AMDGPU/regression/bug28538.s
@@ -0,0 +1,12 @@
+// RUN: not llvm-mc -arch=amdgcn -mcpu=tonga -show-encoding %s 2>&1 | FileCheck %s --check-prefix=NOCIVI --check-prefix=NOVI
+// RUN: not llvm-mc -arch=amdgcn -show-encoding %s 2>&1 | FileCheck %s --check-prefix=NOSI --check-prefix=NOSICI
+// RUN: not llvm-mc -arch=amdgcn -mcpu=SI -show-encoding %s 2>&1 | FileCheck %s --check-prefix=NOSI --check-prefix=NOSICI
+// RUN: not llvm-mc -arch=amdgcn -mcpu=bonaire -show-encoding %s 2>&1 | FileCheck %s --check-prefix=NOSICI
+
+// NOSICI: error:
+// NOVI: error: failed parsing operand
+v_mov_b32 v0, v0 row_bcast:0
+
+// NOSICI: error:
+// NOVI: error: failed parsing operand
+v_mov_b32 v0, v0 row_bcast:13