[AArch64] Check the size of the vector before accessing its elements.

This fixes an assert in AArch64AsmParser::MatchAndEmitInstruction.

rdar://problem/23081753

llvm-svn: 250207

2 files changed, 10 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
index e3af43d1948..3980d3698c1 100644
--- a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -3967,7 +3967,7 @@ bool AArch64AsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
     // suffix token operand.  The short-form match failure is probably more
     // relevant: use it instead.
     if (MatchResult == Match_InvalidOperand && ErrorInfo == 1 &&
-        ((AArch64Operand &)*Operands[1]).isToken() &&
+        Operands.size() > 1 && ((AArch64Operand &)*Operands[1]).isToken() &&
         ((AArch64Operand &)*Operands[1]).isTokenSuffix()) {
       MatchResult = ShortFormNEONMatchResult;
       ErrorInfo = ShortFormNEONErrorInfo;
diff --git a/llvm/test/MC/AArch64/arm64-diags.s b/llvm/test/MC/AArch64/arm64-diags.s
index e368d50f3b2..3510193a71f 100644
--- a/llvm/test/MC/AArch64/arm64-diags.s
+++ b/llvm/test/MC/AArch64/arm64-diags.s
@@ -480,3 +480,12 @@ tlbi vale3
 ; CHECK-ERRORS: error: invalid operand for instruction
 ; CHECK-ERRORS:   b.eq 0, 0
 ; CHECK-ERRORS:           ^
+
+; Check that we give the proper "too few operands" diagnostic instead of
+; asserting.
+
+  ldr
+
+; CHECK-ERRORS: error: too few operands for instruction
+; CHECK-ERRORS:   ldr
+; CHECK-ERRORS:   ^