[llvm] Prefer StringRef::substr to StringRef::slice (NFC) (#105943)

S.substr(N) is simpler than S.slice(N, StringRef::npos) and
S.slice(N, S.size()). Also, substr is probably better recognizable
than slice thanks to std::string_view::substr.

Author: kazutakahirata

llvm/include/llvm/ADT/StringRef.h

@@ -713,7 +713,7 @@ namespace llvm {
       size_t Idx = find(Separator);
       if (Idx == npos)
         return std::make_pair(*this, StringRef());
-      return std::make_pair(slice(0, Idx), slice(Idx + Separator.size(), npos));
+      return std::make_pair(slice(0, Idx), substr(Idx + Separator.size()));
     }
 
     /// Split into two substrings around the last occurrence of a separator
@@ -731,7 +731,7 @@ namespace llvm {
       size_t Idx = rfind(Separator);
       if (Idx == npos)
         return std::make_pair(*this, StringRef());
-      return std::make_pair(slice(0, Idx), slice(Idx + Separator.size(), npos));
+      return std::make_pair(slice(0, Idx), substr(Idx + Separator.size()));
     }
 
     /// Split into substrings around the occurrences of a separator string.

llvm/lib/CodeGen/MIRParser/MIParser.cpp

@@ -580,7 +580,7 @@ MIParser::MIParser(PerFunctionMIParsingState &PFS, SMDiagnostic &Error,
 
 void MIParser::lex(unsigned SkipChar) {
   CurrentSource = lexMIToken(
-      CurrentSource.slice(SkipChar, StringRef::npos), Token,
+      CurrentSource.substr(SkipChar), Token,
       [this](StringRef::iterator Loc, const Twine &Msg) { error(Loc, Msg); });
 }
 
@@ -2306,7 +2306,7 @@ bool MIParser::parseDIExpression(MDNode *&Expr) {
   Expr = llvm::parseDIExpressionBodyAtBeginning(
       CurrentSource, Read, Error, *PFS.MF.getFunction().getParent(),
       &PFS.IRSlots);
-  CurrentSource = CurrentSource.slice(Read, StringRef::npos);
+  CurrentSource = CurrentSource.substr(Read);
   lex();
   if (!Expr)
     return error(Error.getMessage());

llvm/lib/MC/MCAsmStreamer.cpp

@@ -491,7 +491,7 @@ void MCAsmStreamer::addExplicitComment(const Twine &T) {
     ExplicitCommentToEmit.append("\t");
     ExplicitCommentToEmit.append(MAI->getCommentString());
     // drop //
-    ExplicitCommentToEmit.append(c.slice(2, c.size()).str());
+    ExplicitCommentToEmit.append(c.substr(2).str());
   } else if (c.starts_with(StringRef("/*"))) {
     size_t p = 2, len = c.size() - 2;
     // emit each line in comment as separate newline.
@@ -512,7 +512,7 @@ void MCAsmStreamer::addExplicitComment(const Twine &T) {
 
     ExplicitCommentToEmit.append("\t");
     ExplicitCommentToEmit.append(MAI->getCommentString());
-    ExplicitCommentToEmit.append(c.slice(1, c.size()).str());
+    ExplicitCommentToEmit.append(c.substr(1).str());
   } else
     assert(false && "Unexpected Assembly Comment");
   // full line comments immediately output

llvm/lib/Object/MachOObjectFile.cpp

@@ -2436,12 +2436,12 @@ StringRef MachOObjectFile::guessLibraryShortName(StringRef Name,
   a = Name.rfind('/');
   if (a == Name.npos || a == 0)
     goto guess_library;
-  Foo = Name.slice(a+1, Name.npos);
+  Foo = Name.substr(a + 1);
 
   // Look for a suffix starting with a '_'
   Idx = Foo.rfind('_');
   if (Idx != Foo.npos && Foo.size() >= 2) {
-    Suffix = Foo.slice(Idx, Foo.npos);
+    Suffix = Foo.substr(Idx);
     if (Suffix != "_debug" && Suffix != "_profile")
       Suffix = StringRef();
     else
@@ -2468,7 +2468,7 @@ StringRef MachOObjectFile::guessLibraryShortName(StringRef Name,
   c =  Name.rfind('/', b);
   if (c == Name.npos || c == 0)
     goto guess_library;
-  V = Name.slice(c+1, Name.npos);
+  V = Name.substr(c + 1);
   if (!V.starts_with("Versions/"))
     goto guess_library;
   d =  Name.rfind('/', c);
@@ -2489,7 +2489,7 @@ StringRef MachOObjectFile::guessLibraryShortName(StringRef Name,
   a = Name.rfind('.');
   if (a == Name.npos || a == 0)
     return StringRef();
-  Dylib = Name.slice(a, Name.npos);
+  Dylib = Name.substr(a);
   if (Dylib != ".dylib")
     goto guess_qtx;
 
@@ -2527,7 +2527,7 @@ StringRef MachOObjectFile::guessLibraryShortName(StringRef Name,
   return Lib;
 
 guess_qtx:
-  Qtx = Name.slice(a, Name.npos);
+  Qtx = Name.substr(a);
   if (Qtx != ".qtx")
     return StringRef();
   b = Name.rfind('/', a);

llvm/lib/Support/StringRef.cpp

@@ -328,7 +328,7 @@ void StringRef::split(SmallVectorImpl<StringRef> &A,
       A.push_back(S.slice(0, Idx));
 
     // Jump forward.
-    S = S.slice(Idx + Separator.size(), npos);
+    S = S.substr(Idx + Separator.size());
   }
 
   // Push the tail.
@@ -354,7 +354,7 @@ void StringRef::split(SmallVectorImpl<StringRef> &A, char Separator,
       A.push_back(S.slice(0, Idx));
 
     // Jump forward.
-    S = S.slice(Idx + 1, npos);
+    S = S.substr(Idx + 1);
   }
 
   // Push the tail.

llvm/lib/Support/VirtualFileSystem.cpp

@@ -2780,7 +2780,7 @@ bool JSONWriter::containedIn(StringRef Parent, StringRef Path) {
 StringRef JSONWriter::containedPart(StringRef Parent, StringRef Path) {
   assert(!Parent.empty());
   assert(containedIn(Parent, Path));
-  return Path.slice(Parent.size() + 1, StringRef::npos);
+  return Path.substr(Parent.size() + 1);
 }
 
 void JSONWriter::startDirectory(StringRef Path) {
@@ -2846,7 +2846,7 @@ void JSONWriter::write(ArrayRef<YAMLVFSEntry> Entries,
     if (UseOverlayRelative) {
       assert(RPath.starts_with(OverlayDir) &&
              "Overlay dir must be contained in RPath");
-      RPath = RPath.slice(OverlayDir.size(), RPath.size());
+      RPath = RPath.substr(OverlayDir.size());
     }
 
     bool IsCurrentDirEmpty = true;
@@ -2879,7 +2879,7 @@ void JSONWriter::write(ArrayRef<YAMLVFSEntry> Entries,
       if (UseOverlayRelative) {
         assert(RPath.starts_with(OverlayDir) &&
                "Overlay dir must be contained in RPath");
-        RPath = RPath.slice(OverlayDir.size(), RPath.size());
+        RPath = RPath.substr(OverlayDir.size());
       }
       if (!Entry.IsDirectory) {
         writeEntry(path::filename(Entry.VPath), RPath);

llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

@@ -4183,7 +4183,7 @@ ParseStatus AArch64AsmParser::tryParseVectorRegister(MCRegister &Reg,
 
   if (RegNum) {
     if (Next != StringRef::npos) {
-      Kind = Name.slice(Next, StringRef::npos);
+      Kind = Name.substr(Next);
       if (!isValidVectorKind(Kind, MatchKind))
         return TokError("invalid vector kind qualifier");
     }

llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp

@@ -5251,7 +5251,7 @@ ParseStatus ARMAsmParser::parseMSRMaskOperand(OperandVector &Operands) {
   StringRef Flags = "";
   std::string SpecReg = Mask.slice(Start, Next).lower();
   if (Next != StringRef::npos)
-    Flags = Mask.slice(Next+1, Mask.size());
+    Flags = Mask.substr(Next + 1);
 
   // FlagsVal contains the complete mask:
   // 3-0: Mask
@@ -6648,15 +6648,15 @@ StringRef ARMAsmParser::splitMnemonic(StringRef Mnemonic, StringRef ExtraToken,
 
   // The "it" instruction has the condition mask on the end of the mnemonic.
   if (Mnemonic.starts_with("it")) {
-    ITMask = Mnemonic.slice(2, Mnemonic.size());
+    ITMask = Mnemonic.substr(2);
     Mnemonic = Mnemonic.slice(0, 2);
   }
 
   if (Mnemonic.starts_with("vpst")) {
-    ITMask = Mnemonic.slice(4, Mnemonic.size());
+    ITMask = Mnemonic.substr(4);
     Mnemonic = Mnemonic.slice(0, 4);
   } else if (Mnemonic.starts_with("vpt")) {
-    ITMask = Mnemonic.slice(3, Mnemonic.size());
+    ITMask = Mnemonic.substr(3);
     Mnemonic = Mnemonic.slice(0, 3);
   }
 

llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp

@@ -1682,7 +1682,7 @@ bool PPCAsmParser::ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
     Operands.push_back(PPCOperand::CreateToken(Mnemonic, NameLoc, isPPC64()));
   if (Dot != StringRef::npos) {
     SMLoc DotLoc = SMLoc::getFromPointer(NameLoc.getPointer() + Dot);
-    StringRef DotStr = Name.slice(Dot, StringRef::npos);
+    StringRef DotStr = Name.substr(Dot);
     if (!NewOpcode.empty()) // Underlying memory for Name is volatile.
       Operands.push_back(
           PPCOperand::CreateTokenWithStringCopy(DotStr, DotLoc, isPPC64()));

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

@@ -1957,7 +1957,7 @@ bool X86AsmParser::ParseIntelExpression(IntelExprStateMachine &SM, SMLoc &End) {
           consumeToken();
           StringRef LHS = Identifier.slice(0, DotOffset);
           StringRef Dot = Identifier.slice(DotOffset, DotOffset + 1);
-          StringRef RHS = Identifier.slice(DotOffset + 1, StringRef::npos);
+          StringRef RHS = Identifier.substr(DotOffset + 1);
           if (!RHS.empty()) {
             getLexer().UnLex(AsmToken(AsmToken::Identifier, RHS));
           }

llvm/lib/TargetParser/RISCVISAInfo.cpp

@@ -508,7 +508,7 @@ RISCVISAInfo::parseNormalizedArchString(StringRef Arch) {
 
     size_t Idx = Arch.find('_');
     StringRef Ext = Arch.slice(0, Idx);
-    Arch = Arch.slice(Idx, StringRef::npos);
+    Arch = Arch.substr(Idx);
 
     StringRef Prefix, MinorVersionStr;
     std::tie(Prefix, MinorVersionStr) = Ext.rsplit('p');
@@ -533,7 +533,7 @@ RISCVISAInfo::parseNormalizedArchString(StringRef Arch) {
       return getError("missing extension name");
 
     StringRef ExtName = Prefix.slice(0, VersionStart);
-    StringRef MajorVersionStr = Prefix.slice(VersionStart, StringRef::npos);
+    StringRef MajorVersionStr = Prefix.substr(VersionStart);
     if (MajorVersionStr.getAsInteger(10, MajorVersion))
       return getError("failed to parse major version number");
 
@@ -662,7 +662,7 @@ RISCVISAInfo::parseArchString(StringRef Arch, bool EnableExperimentalExtension,
 
     size_t Idx = Arch.find('_');
     StringRef Ext = Arch.slice(0, Idx);
-    Arch = Arch.slice(Idx, StringRef::npos);
+    Arch = Arch.substr(Idx);
 
     do {
       StringRef Name, Vers, Desc;

llvm/utils/TableGen/AsmMatcherEmitter.cpp

@@ -849,14 +849,14 @@ parseTwoOperandConstraint(StringRef S, ArrayRef<SMLoc> Loc) {
   size_t start = Ops.first.find_first_of('$');
   if (start == std::string::npos)
     PrintFatalError(Loc, "expected '$' prefix on asm operand name");
-  Ops.first = Ops.first.slice(start + 1, std::string::npos);
+  Ops.first = Ops.first.substr(start + 1);
   size_t end = Ops.first.find_last_of(" \t");
   Ops.first = Ops.first.slice(0, end);
   // Now the second operand.
   start = Ops.second.find_first_of('$');
   if (start == std::string::npos)
     PrintFatalError(Loc, "expected '$' prefix on asm operand name");
-  Ops.second = Ops.second.slice(start + 1, std::string::npos);
+  Ops.second = Ops.second.substr(start + 1);
   end = Ops.second.find_last_of(" \t");
   Ops.first = Ops.first.slice(0, end);
   return Ops;

llvm/utils/TableGen/OptParserEmitter.cpp

@@ -178,7 +178,7 @@ static MarshallingInfo createMarshallingInfo(const Record &R) {
         break;
       if (Idx > 0)
         Ret.Values.push_back(ValuesStr.slice(0, Idx));
-      ValuesStr = ValuesStr.slice(Idx + 1, StringRef::npos);
+      ValuesStr = ValuesStr.substr(Idx + 1);
     }
     if (!ValuesStr.empty())
       Ret.Values.push_back(ValuesStr);