Index: lib/Target/AMDGPU/MCTargetDesc/AMDGPUAsmBackend.cpp
===================================================================
--- lib/Target/AMDGPU/MCTargetDesc/AMDGPUAsmBackend.cpp
+++ lib/Target/AMDGPU/MCTargetDesc/AMDGPUAsmBackend.cpp
@@ -92,8 +92,12 @@
 
   switch ((unsigned)Fixup.getKind()) {
     case AMDGPU::fixup_si_sopp_br: {
+      int64_t BrImm = (Value - 4) / 4;
+      if (!isInt<16>(BrImm))
+        report_fatal_error("branch size exceeds simm16");
+
       uint16_t *Dst = (uint16_t*)(Data + Fixup.getOffset());
-      *Dst = (Value - 4) / 4;
+      *Dst = BrImm;
       break;
     }