[llvm] r332866 - Fix ubsan bounds check failure.

[Peter Collingbourne via llvm-commits]

Author: pcc
Date: Mon May 21 12:09:47 2018
New Revision: 332866

URL: http://llvm.org/viewvc/llvm-project?rev=332866&view=rev
Log:
Fix ubsan bounds check failure.

Modified:
    llvm/trunk/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

Modified: llvm/trunk/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp?rev=332866&r1=332865&r2=332866&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp (original)
+++ llvm/trunk/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp Mon May 21 12:09:47 2018
@@ -365,7 +365,8 @@ bool X86AsmBackend::writeNopData(raw_ost
     for (uint8_t i = 0; i < Prefixes; i++)
       OS << '\x66';
     const uint8_t Rest = ThisNopLength - Prefixes;
-    OS.write(Nops[Rest - 1], Rest);
+    if (Rest != 0)
+      OS.write(Nops[Rest - 1], Rest);
     Count -= ThisNopLength;
   } while (Count != 0);