Index: llvm/include/llvm/MC/MCAsmInfo.h
===================================================================
--- llvm/include/llvm/MC/MCAsmInfo.h
+++ llvm/include/llvm/MC/MCAsmInfo.h
@@ -122,10 +122,14 @@
   /// other when on the same line.  Defaults to ';'
   const char *SeparatorString;
 
-  /// This indicates the comment character used by the assembler.  Defaults to
+  /// This indicates the comment string used by the assembler.  Defaults to
   /// "#"
   StringRef CommentString;
 
+  /// This indicates whether the comment string is only accepted as a comment
+  /// at the beginning of statements. Defaults to false.
+  bool RestrictCommentStringToStartOfStatement = false;
+
   /// This is appended to emitted labels.  Defaults to ":"
   const char *LabelSuffix;
 
@@ -549,6 +553,9 @@
   unsigned getCommentColumn() const { return 40; }
 
   StringRef getCommentString() const { return CommentString; }
+  bool getRestrictCommentStringToStartOfStatement() const {
+    return RestrictCommentStringToStartOfStatement;
+  }
   const char *getLabelSuffix() const { return LabelSuffix; }
 
   bool useAssignmentForEHBegin() const { return UseAssignmentForEHBegin; }
Index: llvm/lib/MC/MCParser/AsmLexer.cpp
===================================================================
--- llvm/lib/MC/MCParser/AsmLexer.cpp
+++ llvm/lib/MC/MCParser/AsmLexer.cpp
@@ -659,6 +659,9 @@
 }
 
 bool AsmLexer::isAtStartOfComment(const char *Ptr) {
+  if (MAI.getRestrictCommentStringToStartOfStatement() && !IsAtStartOfStatement)
+    return false;
+
   StringRef CommentString = MAI.getCommentString();
 
   if (CommentString.size() == 1)
Index: llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmInfo.cpp
===================================================================
--- llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmInfo.cpp
+++ llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmInfo.cpp
@@ -23,7 +23,8 @@
 
   MaxInstLength = 6;
 
-  CommentString = "#";
+  CommentString = AssemblerDialect == AD_HLASM ? "*" : "#";
+  RestrictCommentStringToStartOfStatement = (AssemblerDialect == AD_HLASM);
   ZeroDirective = "\t.space\t";
   Data64bitsDirective = "\t.quad\t";
   UsesELFSectionDirectiveForBSS = true;