[AIX] asm output: use character literals in byte lists for strings

This patch improves the assembly output produced for string literals by
using character literals in byte lists. This provides the benefits of
having printable characters appear as such in the assembly output and of
having strings kept as logical units on the same line.

Reviewed By: daltenty

Differential Revision: https://reviews.llvm.org/D80953

Author: hubert-reinterpretcast

llvm/include/llvm/MC/MCAsmInfo.h

@@ -54,6 +54,15 @@ enum LCOMMType { NoAlignment, ByteAlignment, Log2Alignment };
 /// This class is intended to be used as a base class for asm
 /// properties and features specific to the target.
 class MCAsmInfo {
+public:
+  /// Assembly character literal syntax types.
+  enum AsmCharLiteralSyntax {
+    ACLS_Unknown, /// Unknown; character literals not used by LLVM for this
+                  /// target.
+    ACLS_SingleQuotePrefix, /// The desired character is prefixed by a single
+                            /// quote, e.g., `'A`.
+  };
+
 protected:
   //===------------------------------------------------------------------===//
   // Properties to be set by the target writer, used to configure asm printer.
@@ -200,6 +209,16 @@ class MCAsmInfo {
   /// 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;
+
+  /// Form used 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 ACLS_Unknown.  Defaults to ACLS_Unknown.
+  AsmCharLiteralSyntax CharacterLiteralSyntax = ACLS_Unknown;
+
   /// 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",
@@ -562,6 +581,10 @@ class MCAsmInfo {
   }
   const char *getAsciiDirective() const { return AsciiDirective; }
   const char *getAscizDirective() const { return AscizDirective; }
+  const char *getByteListDirective() const { return ByteListDirective; }
+  AsmCharLiteralSyntax characterLiteralSyntax() const {
+    return CharacterLiteralSyntax;
+  }
   bool getAlignmentIsInBytes() const { return AlignmentIsInBytes; }
   unsigned getTextAlignFillValue() const { return TextAlignFillValue; }
   const char *getGlobalDirective() const { return GlobalDirective; }

llvm/lib/MC/MCAsmInfoXCOFF.cpp

@@ -24,6 +24,8 @@ MCAsmInfoXCOFF::MCAsmInfoXCOFF() {
   ZeroDirectiveSupportsNonZeroValue = false;
   AsciiDirective = nullptr; // not supported
   AscizDirective = nullptr; // not supported
+  ByteListDirective = "\t.byte\t";
+  CharacterLiteralSyntax = ACLS_SingleQuotePrefix;
 
   // Use .vbyte for data definition to avoid directives that apply an implicit
   // alignment.

llvm/lib/MC/MCAsmStreamer.cpp

@@ -971,6 +971,47 @@ void MCAsmStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 
 static inline char toOctal(int X) { return (X&7)+'0'; }
 
+static void PrintByteList(StringRef Data, raw_ostream &OS,
+                          MCAsmInfo::AsmCharLiteralSyntax ACLS) {
+  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 printOneCharacterFor = [printCharacterInOctal](
+                                        auto printOnePrintingCharacter) {
+    return [printCharacterInOctal, printOnePrintingCharacter](unsigned char C) {
+      if (isPrint(C)) {
+        printOnePrintingCharacter(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));
+  };
+  switch (ACLS) {
+  case MCAsmInfo::ACLS_Unknown:
+    printCharacterList(printCharacterInOctal);
+    return;
+  case MCAsmInfo::ACLS_SingleQuotePrefix:
+    printCharacterList(printOneCharacterFor([&OS](char C) {
+      const char AsmCharLitBuf[2] = {'\'', C};
+      OS << StringRef(AsmCharLitBuf, sizeof(AsmCharLitBuf));
+    }));
+    return;
+  }
+  llvm_unreachable("Invalid AsmCharLiteralSyntax value!");
+}
+
 static void PrintQuotedString(StringRef Data, raw_ostream &OS) {
   OS << '"';
 
@@ -1009,33 +1050,42 @@ void MCAsmStreamer::emitBytes(StringRef Data) {
          "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->characterLiteralSyntax());
+      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) {

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

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

llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll

@@ -41,30 +41,9 @@ entry:
 ; CHECK-NEXT:   .vbyte	4, 0                       # 0x0
 ; CHECK-NEXT:   .csect .rodata.str1.1[RO],2
 ; CHECK-NEXT: L..strA:
-; 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

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: