diff --git a/llvm/include/llvm/MC/MCAsmInfo.h b/llvm/include/llvm/MC/MCAsmInfo.h
--- a/llvm/include/llvm/MC/MCAsmInfo.h
+++ b/llvm/include/llvm/MC/MCAsmInfo.h
@@ -196,6 +196,16 @@
   /// doesn't support this, it can be set to null.  Defaults to "\t.asciz\t"
   const char *AscizDirective;
 
+  /// This directive accepts a comma-separated list of bytes for emission as a
+  /// string of bytes.  For targets that do not support this, it shall be set to
+  /// null.  Defaults to null.
+  const char *ByteListDirective = nullptr;
+
+  /// Format string in the style of printf for character literals in the
+  /// assembly syntax.  Useful for producing strings as byte lists.  If a target
+  /// does not use or support this, it shall be set to null.  Defaults to null.
+  const char *CharacterLiteralFormatString = nullptr;
+
   /// These directives are used to output some unit of integer data to the
   /// current section.  If a data directive is set to null, smaller data
   /// directives will be used to emit the large sizes.  Defaults to "\t.byte\t",
@@ -563,6 +573,10 @@
   }
   const char *getAsciiDirective() const { return AsciiDirective; }
   const char *getAscizDirective() const { return AscizDirective; }
+  const char *getByteListDirective() const { return ByteListDirective; }
+  const char *characterLiteralFormatString() const {
+    return CharacterLiteralFormatString;
+  }
   bool getAlignmentIsInBytes() const { return AlignmentIsInBytes; }
   unsigned getTextAlignFillValue() const { return TextAlignFillValue; }
   const char *getGlobalDirective() const { return GlobalDirective; }
diff --git a/llvm/lib/MC/MCAsmInfoXCOFF.cpp b/llvm/lib/MC/MCAsmInfoXCOFF.cpp
--- a/llvm/lib/MC/MCAsmInfoXCOFF.cpp
+++ b/llvm/lib/MC/MCAsmInfoXCOFF.cpp
@@ -22,6 +22,8 @@
   ZeroDirectiveSupportsNonZeroValue = false;
   AsciiDirective = nullptr; // not supported
   AscizDirective = nullptr; // not supported
+  ByteListDirective = "\t.byte\t";
+  CharacterLiteralFormatString = "'%c"; // single quote + the character
 
   // Use .vbyte for data definition to avoid directives that apply an implicit
   // alignment.
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -890,6 +890,38 @@
 
 static inline char toOctal(int X) { return (X&7)+'0'; }
 
+static void PrintByteList(StringRef Data, raw_ostream &OS,
+                          const char *CharacterLiteralFormatString) {
+  assert(!Data.empty() && "Cannot generate an empty list.");
+  const auto printCharacterInOctal = [&OS](unsigned char C) {
+    OS << '0';
+    OS << toOctal(C >> 6);
+    OS << toOctal(C >> 3);
+    OS << toOctal(C >> 0);
+  };
+  const auto printOneCharacter = [&OS, CharacterLiteralFormatString,
+                                  printCharacterInOctal](unsigned char C) {
+    if (isPrint(C)) {
+      OS << format(CharacterLiteralFormatString, static_cast<char>(C));
+      return;
+    }
+    printCharacterInOctal(C);
+  };
+  const auto printCharacterList = [Data, &OS](const auto &printOneCharacter) {
+    const auto BeginPtr = Data.begin(), EndPtr = Data.end();
+    for (const unsigned char C : make_range(BeginPtr, EndPtr - 1)) {
+      printOneCharacter(C);
+      OS << ',';
+    }
+    printOneCharacter(*(EndPtr - 1));
+  };
+  if (LLVM_LIKELY(CharacterLiteralFormatString)) {
+    printCharacterList(printOneCharacter);
+    return;
+  }
+  printCharacterList(printCharacterInOctal);
+}
+
 static void PrintQuotedString(StringRef Data, raw_ostream &OS) {
   OS << '"';
 
@@ -928,33 +960,42 @@
          "Cannot emit contents before setting section!");
   if (Data.empty()) return;
 
-  // If only single byte is provided or no ascii or asciz directives is
-  // supported, emit as vector of 8bits data.
-  if (Data.size() == 1 ||
-      !(MAI->getAscizDirective() || MAI->getAsciiDirective())) {
-    if (MCTargetStreamer *TS = getTargetStreamer()) {
-      TS->emitRawBytes(Data);
+  const auto emitAsString = [this](StringRef Data) {
+    // If the data ends with 0 and the target supports .asciz, use it, otherwise
+    // use .ascii or a byte-list directive
+    if (MAI->getAscizDirective() && Data.back() == 0) {
+      OS << MAI->getAscizDirective();
+      Data = Data.substr(0, Data.size() - 1);
+    } else if (LLVM_LIKELY(MAI->getAsciiDirective())) {
+      OS << MAI->getAsciiDirective();
+    } else if (MAI->getByteListDirective()) {
+      OS << MAI->getByteListDirective();
+      PrintByteList(Data, OS, MAI->characterLiteralFormatString());
+      EmitEOL();
+      return true;
     } else {
-      const char *Directive = MAI->getData8bitsDirective();
-      for (const unsigned char C : Data.bytes()) {
-        OS << Directive << (unsigned)C;
-        EmitEOL();
-      }
+      return false;
     }
+
+    PrintQuotedString(Data, OS);
+    EmitEOL();
+    return true;
+  };
+
+  if (Data.size() != 1 && emitAsString(Data))
     return;
-  }
 
-  // If the data ends with 0 and the target supports .asciz, use it, otherwise
-  // use .ascii
-  if (MAI->getAscizDirective() && Data.back() == 0) {
-    OS << MAI->getAscizDirective();
-    Data = Data.substr(0, Data.size()-1);
-  } else {
-    OS << MAI->getAsciiDirective();
+  // Only single byte is provided or no ascii, asciz, or byte-list directives
+  // are applicable. Emit as vector of individual 8bits data elements.
+  if (MCTargetStreamer *TS = getTargetStreamer()) {
+    TS->emitRawBytes(Data);
+    return;
+  }
+  const char *Directive = MAI->getData8bitsDirective();
+  for (const unsigned char C : Data.bytes()) {
+    OS << Directive << (unsigned)C;
+    EmitEOL();
   }
-
-  PrintQuotedString(Data, OS);
-  EmitEOL();
 }
 
 void MCAsmStreamer::emitBinaryData(StringRef Data) {
diff --git a/llvm/test/CodeGen/PowerPC/aix-bytestring.ll b/llvm/test/CodeGen/PowerPC/aix-bytestring.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/aix-bytestring.ll
@@ -0,0 +1,7 @@
+; RUN: llc -verify-machineinstrs -mcpu=pwr7 -mtriple powerpc-ibm-aix-xcoff < %s | FileCheck %s
+; RUN: llc -verify-machineinstrs -mcpu=pwr7 -mtriple powerpc64-ibm-aix-xcoff < %s | FileCheck %s
+
+@str = constant [256 x i8] c"\01\02\03\04\05\06\07\08\09\0A\0B\0C\0D\0E\0F\10\11\12\13\14\15\16\17\18\19\1A\1B\1C\1D\1E\1F !\22#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\7F\80\81\82\83\84\85\86\87\88\89\8A\8B\8C\8D\8E\8F\90\91\92\93\94\95\96\97\98\99\9A\9B\9C\9D\9E\9F\A0\A1\A2\A3\A4\A5\A6\A7\A8\A9\AA\AB\AC\AD\AE\AF\B0\B1\B2\B3\B4\B5\B6\B7\B8\B9\BA\BB\BC\BD\BE\BF\C0\C1\C2\C3\C4\C5\C6\C7\C8\C9\CA\CB\CC\CD\CE\CF\D0\D1\D2\D3\D4\D5\D6\D7\D8\D9\DA\DB\DC\DD\DE\DF\E0\E1\E2\E3\E4\E5\E6\E7\E8\E9\EA\EB\EC\ED\EE\EF\F0\F1\F2\F3\F4\F5\F6\F7\F8\F9\FA\FB\FC\FD\FE\FF\00", align 1
+
+; CHECK-LABEL:str:
+;  CHECK-NEXT:        .byte   0001,0002,0003,0004,0005,0006,0007,0010,0011,0012,0013,0014,0015,0016,0017,0020,0021,0022,0023,0024,0025,0026,0027,0030,0031,0032,0033,0034,0035,0036,0037,' ,'!,'",'#,'$,'%,'&,'','(,'),'*,'+,',,'-,'.,'/,'0,'1,'2,'3,'4,'5,'6,'7,'8,'9,':,';,'<,'=,'>,'?,'@,'A,'B,'C,'D,'E,'F,'G,'H,'I,'J,'K,'L,'M,'N,'O,'P,'Q,'R,'S,'T,'U,'V,'W,'X,'Y,'Z,'[,'\,'],'^,'_,'`,'a,'b,'c,'d,'e,'f,'g,'h,'i,'j,'k,'l,'m,'n,'o,'p,'q,'r,'s,'t,'u,'v,'w,'x,'y,'z,'{,'|,'},'~,0177,0200,0201,0202,0203,0204,0205,0206,0207,0210,0211,0212,0213,0214,0215,0216,0217,0220,0221,0222,0223,0224,0225,0226,0227,0230,0231,0232,0233,0234,0235,0236,0237,0240,0241,0242,0243,0244,0245,0246,0247,0250,0251,0252,0253,0254,0255,0256,0257,0260,0261,0262,0263,0264,0265,0266,0267,0270,0271,0272,0273,0274,0275,0276,0277,0300,0301,0302,0303,0304,0305,0306,0307,0310,0311,0312,0313,0314,0315,0316,0317,0320,0321,0322,0323,0324,0325,0326,0327,0330,0331,0332,0333,0334,0335,0336,0337,0340,0341,0342,0343,0344,0345,0346,0347,0350,0351,0352,0353,0354,0355,0356,0357,0360,0361,0362,0363,0364,0365,0366,0367,0370,0371,0372,0373,0374,0375,0376,0377,0000
diff --git a/llvm/test/CodeGen/PowerPC/aix-xcoff-data.ll b/llvm/test/CodeGen/PowerPC/aix-xcoff-data.ll
--- a/llvm/test/CodeGen/PowerPC/aix-xcoff-data.ll
+++ b/llvm/test/CodeGen/PowerPC/aix-xcoff-data.ll
@@ -86,10 +86,7 @@
 
 ; CHECK:      .globl  chrarray
 ; CHECK-NEXT: chrarray:
-; CHECK-NEXT: .byte   97
-; CHECK-NEXT: .byte   98
-; CHECK-NEXT: .byte   99
-; CHECK-NEXT: .byte   100
+; CHECK-NEXT: .byte   'a,'b,'c,'d
 
 ; CHECK:      .globl  dblarr
 ; CHECK-NEXT: .align  3
diff --git a/llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll b/llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll
--- a/llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll
+++ b/llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll
@@ -41,30 +41,9 @@
 ; CHECK-NEXT:   .vbyte	4, 0                       # 0x0
 ; CHECK-NEXT:   .csect .rodata.str1.1[RO],2
 ; CHECK-NEXT: .LstrA:
-; CHECK-NEXT: .byte   104
-; CHECK-NEXT: .byte   101
-; CHECK-NEXT: .byte   108
-; CHECK-NEXT: .byte   108
-; CHECK-NEXT: .byte   111
-; CHECK-NEXT: .byte   32
-; CHECK-NEXT: .byte   119
-; CHECK-NEXT: .byte   111
-; CHECK-NEXT: .byte   114
-; CHECK-NEXT: .byte   108
-; CHECK-NEXT: .byte   100
-; CHECK-NEXT: .byte   33
-; CHECK-NEXT: .byte   10
-; CHECK-NEXT: .byte   0
+; CHECK-NEXT: .byte   'h,'e,'l,'l,'o,' ,'w,'o,'r,'l,'d,'!,0012,0000
 ; CHECK-NEXT: .L.str:
-; CHECK-NEXT: .byte   97
-; CHECK-NEXT: .byte   98
-; CHECK-NEXT: .byte   99
-; CHECK-NEXT: .byte   100
-; CHECK-NEXT: .byte   101
-; CHECK-NEXT: .byte   102
-; CHECK-NEXT: .byte   103
-; CHECK-NEXT: .byte   104
-; CHECK-NEXT: .byte   0
+; CHECK-NEXT: .byte   'a,'b,'c,'d,'e,'f,'g,'h,0000
 
 ; CHECKOBJ:     00000010 <.rodata.str2.2>:
 ; CHECKOBJ-NEXT:       10: 01 08 01 10
diff --git a/llvm/test/CodeGen/PowerPC/aix-xcoff-rodata.ll b/llvm/test/CodeGen/PowerPC/aix-xcoff-rodata.ll
--- a/llvm/test/CodeGen/PowerPC/aix-xcoff-rodata.ll
+++ b/llvm/test/CodeGen/PowerPC/aix-xcoff-rodata.ll
@@ -53,10 +53,7 @@
 ; CHECK64-NEXT:        .vbyte	8, 0x408c200000000000
 ; CHECK-NEXT:          .globl  const_chrarray
 ; CHECK-NEXT:  const_chrarray:
-; CHECK-NEXT:          .byte   97
-; CHECK-NEXT:          .byte   98
-; CHECK-NEXT:          .byte   99
-; CHECK-NEXT:          .byte   100
+; CHECK-NEXT:          .byte   'a,'b,'c,'d
 ; CHECK-NEXT:          .globl  const_dblarr
 ; CHECK-NEXT:          .align  3
 ; CHECK-NEXT:  const_dblarr: