From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 8 Dec 2017 22:32:35 +0000 (+0000)
Subject: Avoid constructing an out-of-range value for an enumeration (which results in UB).
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c502040075a582f6fa7782476a884e30b532da2a;p=llvm

Avoid constructing an out-of-range value for an enumeration (which results in UB).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320206 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/utils/TableGen/X86RecognizableInstr.cpp b/utils/TableGen/X86RecognizableInstr.cpp
index c3330294d76..9afdd7e0963 100644
--- a/utils/TableGen/X86RecognizableInstr.cpp
+++ b/utils/TableGen/X86RecognizableInstr.cpp
@@ -706,7 +706,7 @@ void RecognizableInstr::emitDecodePath(DisassemblerTables &tables) const {
 #define MAP(from, to)                     \
   case X86Local::MRM_##from:
 
-  OpcodeType    opcodeType  = (OpcodeType)-1;
+  llvm::Optional<OpcodeType> opcodeType;
 
   ModRMFilter*  filter      = nullptr;
   uint8_t       opcodeToSet = 0;
@@ -786,8 +786,7 @@ void RecognizableInstr::emitDecodePath(DisassemblerTables &tables) const {
   case X86Local::AdSize64: AddressSize = 64; break;
   }
 
-  assert(opcodeType != (OpcodeType)-1 &&
-         "Opcode type not set");
+  assert(opcodeType && "Opcode type not set");
   assert(filter && "Filter not set");
 
   if (Form == X86Local::AddRegFrm) {
@@ -799,12 +798,12 @@ void RecognizableInstr::emitDecodePath(DisassemblerTables &tables) const {
     for (currentOpcode = opcodeToSet;
          currentOpcode < opcodeToSet + 8;
          ++currentOpcode)
-      tables.setTableFields(opcodeType, insnContext(), currentOpcode, *filter,
+      tables.setTableFields(*opcodeType, insnContext(), currentOpcode, *filter,
                             UID, Is32Bit, OpPrefix == 0,
                             IgnoresVEX_L || EncodeRC,
                             VEX_WPrefix == X86Local::VEX_WIG, AddressSize);
   } else {
-    tables.setTableFields(opcodeType, insnContext(), opcodeToSet, *filter, UID,
+    tables.setTableFields(*opcodeType, insnContext(), opcodeToSet, *filter, UID,
                           Is32Bit, OpPrefix == 0, IgnoresVEX_L || EncodeRC,
                           VEX_WPrefix == X86Local::VEX_WIG, AddressSize);
   }