[clang] Return std::string_view from TargetInfo::getClobbers()

Change the return type of `getClobbers` function from `const char*`
to `std::string_view`. Update the function usages in CodeGen module.

The reasoning of these changes is to remove unsafe `const char*`
strings and prevent unnecessary allocations for constructing the
`std::string` in usages of `getClobbers()` function.

Differential Revision: https://reviews.llvm.org/D148799

clang/include/clang/Basic/TargetInfo.h

@@ -1178,7 +1178,7 @@ class TargetInfo : public TransferrableTargetInfo,
   }
 
   /// Returns a string of target-specific clobbers, in LLVM format.
-  virtual const char *getClobbers() const = 0;
+  virtual std::string_view getClobbers() const = 0;
 
   /// Returns true if NaN encoding is IEEE 754-2008.
   /// Only MIPS allows a different encoding.

clang/lib/Basic/Targets/AArch64.cpp

@@ -1295,7 +1295,7 @@ bool AArch64TargetInfo::validateConstraintModifier(
   }
 }
 
-const char *AArch64TargetInfo::getClobbers() const { return ""; }
+std::string_view AArch64TargetInfo::getClobbers() const { return ""; }
 
 int AArch64TargetInfo::getEHDataRegisterNumber(unsigned RegNo) const {
   if (RegNo == 0)

clang/lib/Basic/Targets/AArch64.h

@@ -192,7 +192,7 @@ class LLVM_LIBRARY_VISIBILITY AArch64TargetInfo : public TargetInfo {
   bool
   validateConstraintModifier(StringRef Constraint, char Modifier, unsigned Size,
                              std::string &SuggestedModifier) const override;
-  const char *getClobbers() const override;
+  std::string_view getClobbers() const override;
 
   StringRef getConstraintRegister(StringRef Constraint,
                                   StringRef Expression) const override {

clang/lib/Basic/Targets/AMDGPU.h

@@ -117,7 +117,7 @@ class LLVM_LIBRARY_VISIBILITY AMDGPUTargetInfo final : public TargetInfo {
   bool hasBFloat16Type() const override { return isAMDGCN(getTriple()); }
   const char *getBFloat16Mangling() const override { return "u6__bf16"; };
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override;
 

clang/lib/Basic/Targets/ARC.h

@@ -48,7 +48,7 @@ class LLVM_LIBRARY_VISIBILITY ARCTargetInfo : public TargetInfo {
     return TargetInfo::VoidPtrBuiltinVaList;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override {
     static const char *const GCCRegNames[] = {

clang/lib/Basic/Targets/ARM.cpp

@@ -1244,7 +1244,7 @@ bool ARMTargetInfo::validateConstraintModifier(
 
   return true;
 }
-const char *ARMTargetInfo::getClobbers() const {
+std::string_view ARMTargetInfo::getClobbers() const {
   // FIXME: Is this really right?
   return "";
 }

clang/lib/Basic/Targets/ARM.h

@@ -181,7 +181,7 @@ class LLVM_LIBRARY_VISIBILITY ARMTargetInfo : public TargetInfo {
   bool
   validateConstraintModifier(StringRef Constraint, char Modifier, unsigned Size,
                              std::string &SuggestedModifier) const override;
-  const char *getClobbers() const override;
+  std::string_view getClobbers() const override;
 
   StringRef getConstraintRegister(StringRef Constraint,
                                   StringRef Expression) const override {

clang/lib/Basic/Targets/AVR.h

@@ -69,7 +69,7 @@ class LLVM_LIBRARY_VISIBILITY AVRTargetInfo : public TargetInfo {
     return TargetInfo::VoidPtrBuiltinVaList;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override {
     static const char *const GCCRegNames[] = {

clang/lib/Basic/Targets/BPF.h

@@ -60,7 +60,7 @@ class LLVM_LIBRARY_VISIBILITY BPFTargetInfo : public TargetInfo {
 
   ArrayRef<Builtin::Info> getTargetBuiltins() const override;
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   BuiltinVaListKind getBuiltinVaListKind() const override {
     return TargetInfo::VoidPtrBuiltinVaList;

clang/lib/Basic/Targets/CSKY.h

@@ -82,7 +82,7 @@ class LLVM_LIBRARY_VISIBILITY CSKYTargetInfo : public TargetInfo {
   bool validateAsmConstraint(const char *&Name,
                              TargetInfo::ConstraintInfo &info) const override;
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   void getTargetDefines(const LangOptions &Opts,
                         MacroBuilder &Builder) const override;

clang/lib/Basic/Targets/DirectX.h

@@ -77,7 +77,7 @@ class LLVM_LIBRARY_VISIBILITY DirectXTargetInfo : public TargetInfo {
     return std::nullopt;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override {
     return std::nullopt;

clang/lib/Basic/Targets/Hexagon.h

@@ -112,7 +112,7 @@ class LLVM_LIBRARY_VISIBILITY HexagonTargetInfo : public TargetInfo {
 
   ArrayRef<TargetInfo::GCCRegAlias> getGCCRegAliases() const override;
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   static const char *getHexagonCPUSuffix(StringRef Name);
 

clang/lib/Basic/Targets/Lanai.h

@@ -87,7 +87,7 @@ class LLVM_LIBRARY_VISIBILITY LanaiTargetInfo : public TargetInfo {
     return false;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   bool hasBitIntType() const override { return true; }
 };

clang/lib/Basic/Targets/Le64.h

@@ -41,7 +41,7 @@ class LLVM_LIBRARY_VISIBILITY Le64TargetInfo : public TargetInfo {
     return TargetInfo::PNaClABIBuiltinVaList;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override {
     return std::nullopt;

clang/lib/Basic/Targets/LoongArch.h

@@ -51,7 +51,7 @@ class LLVM_LIBRARY_VISIBILITY LoongArchTargetInfo : public TargetInfo {
     return TargetInfo::VoidPtrBuiltinVaList;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override;
 

clang/lib/Basic/Targets/M68k.cpp

@@ -236,7 +236,7 @@ std::string M68kTargetInfo::convertConstraint(const char *&Constraint) const {
   return std::string(1, *Constraint);
 }
 
-const char *M68kTargetInfo::getClobbers() const {
+std::string_view M68kTargetInfo::getClobbers() const {
   // FIXME: Is this really right?
   return "";
 }

clang/lib/Basic/Targets/M68k.h

@@ -49,7 +49,7 @@ class LLVM_LIBRARY_VISIBILITY M68kTargetInfo : public TargetInfo {
   bool validateAsmConstraint(const char *&Name,
                              TargetInfo::ConstraintInfo &info) const override;
   std::optional<std::string> handleAsmEscapedChar(char EscChar) const override;
-  const char *getClobbers() const override;
+  std::string_view getClobbers() const override;
   BuiltinVaListKind getBuiltinVaListKind() const override;
   bool setCPU(const std::string &Name) override;
 };

clang/lib/Basic/Targets/MSP430.h

@@ -87,7 +87,7 @@ class LLVM_LIBRARY_VISIBILITY MSP430TargetInfo : public TargetInfo {
     return false;
   }
 
-  const char *getClobbers() const override {
+  std::string_view getClobbers() const override {
     // FIXME: Is this really right?
     return "";
   }

clang/lib/Basic/Targets/Mips.h

@@ -278,7 +278,7 @@ class LLVM_LIBRARY_VISIBILITY MipsTargetInfo : public TargetInfo {
     return TargetInfo::convertConstraint(Constraint);
   }
 
-  const char *getClobbers() const override {
+  std::string_view getClobbers() const override {
     // In GCC, $1 is not widely used in generated code (it's used only in a few
     // specific situations), so there is no real need for users to add it to
     // the clobbers list if they want to use it in their inline assembly code.

clang/lib/Basic/Targets/NVPTX.h

@@ -109,7 +109,7 @@ class LLVM_LIBRARY_VISIBILITY NVPTXTargetInfo : public TargetInfo {
     }
   }
 
-  const char *getClobbers() const override {
+  std::string_view getClobbers() const override {
     // FIXME: Is this really right?
     return "";
   }

clang/lib/Basic/Targets/PNaCl.h

@@ -69,7 +69,7 @@ class LLVM_LIBRARY_VISIBILITY PNaClTargetInfo : public TargetInfo {
     return false;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   bool hasBitIntType() const override { return true; }
 };

clang/lib/Basic/Targets/PPC.h

@@ -330,7 +330,7 @@ class LLVM_LIBRARY_VISIBILITY PPCTargetInfo : public TargetInfo {
     return R;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
   int getEHDataRegisterNumber(unsigned RegNo) const override {
     if (RegNo == 0)
       return 3;

clang/lib/Basic/Targets/RISCV.h

@@ -60,7 +60,7 @@ class RISCVTargetInfo : public TargetInfo {
     return TargetInfo::VoidPtrBuiltinVaList;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   StringRef getConstraintRegister(StringRef Constraint,
                                   StringRef Expression) const override {

clang/lib/Basic/Targets/SPIR.h

@@ -164,7 +164,7 @@ class LLVM_LIBRARY_VISIBILITY BaseSPIRTargetInfo : public TargetInfo {
     return std::nullopt;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override {
     return std::nullopt;

clang/lib/Basic/Targets/Sparc.h

@@ -77,7 +77,7 @@ class LLVM_LIBRARY_VISIBILITY SparcTargetInfo : public TargetInfo {
     }
     return false;
   }
-  const char *getClobbers() const override {
+  std::string_view getClobbers() const override {
     // FIXME: Implement!
     return "";
   }

clang/lib/Basic/Targets/SystemZ.h

@@ -106,7 +106,7 @@ class LLVM_LIBRARY_VISIBILITY SystemZTargetInfo : public TargetInfo {
     return TargetInfo::convertConstraint(Constraint);
   }
 
-  const char *getClobbers() const override {
+  std::string_view getClobbers() const override {
     // FIXME: Is this really right?
     return "";
   }

clang/lib/Basic/Targets/TCE.h

@@ -99,7 +99,7 @@ class LLVM_LIBRARY_VISIBILITY TCETargetInfo : public TargetInfo {
     return std::nullopt;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   BuiltinVaListKind getBuiltinVaListKind() const override {
     return TargetInfo::VoidPtrBuiltinVaList;

clang/lib/Basic/Targets/VE.h

@@ -69,7 +69,7 @@ class LLVM_LIBRARY_VISIBILITY VETargetInfo : public TargetInfo {
     }
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override {
     static const char *const GCCRegNames[] = {

clang/lib/Basic/Targets/WebAssembly.h

@@ -130,7 +130,7 @@ class LLVM_LIBRARY_VISIBILITY WebAssemblyTargetInfo : public TargetInfo {
     return false;
   }
 
-  const char *getClobbers() const final { return ""; }
+  std::string_view getClobbers() const final { return ""; }
 
   bool isCLZForZeroUndef() const final { return false; }
 

clang/lib/Basic/Targets/X86.h

@@ -262,7 +262,7 @@ class LLVM_LIBRARY_VISIBILITY X86TargetInfo : public TargetInfo {
                                    StringRef Constraint, unsigned Size) const;
 
   std::string convertConstraint(const char *&Constraint) const override;
-  const char *getClobbers() const override {
+  std::string_view getClobbers() const override {
     return "~{dirflag},~{fpsr},~{flags}";
   }
 

clang/lib/Basic/Targets/XCore.h

@@ -49,7 +49,7 @@ class LLVM_LIBRARY_VISIBILITY XCoreTargetInfo : public TargetInfo {
     return TargetInfo::VoidPtrBuiltinVaList;
   }
 
-  const char *getClobbers() const override { return ""; }
+  std::string_view getClobbers() const override { return ""; }
 
   ArrayRef<const char *> getGCCRegNames() const override {
     static const char *const GCCRegNames[] = {

clang/lib/CodeGen/CGBuiltin.cpp

@@ -939,7 +939,7 @@ static llvm::Value *EmitX86BitTestIntrinsic(CodeGenFunction &CGF,
 
   // Build the constraints. FIXME: We should support immediates when possible.
   std::string Constraints = "={@ccc},r,r,~{cc},~{memory}";
-  std::string MachineClobbers = CGF.getTarget().getClobbers();
+  std::string_view MachineClobbers = CGF.getTarget().getClobbers();
   if (!MachineClobbers.empty()) {
     Constraints += ',';
     Constraints += MachineClobbers;
@@ -1082,7 +1082,7 @@ static llvm::Value *emitPPCLoadReserveIntrinsic(CodeGenFunction &CGF,
   AsmOS << "$0, ${1:y}";
 
   std::string Constraints = "=r,*Z,~{memory}";
-  std::string MachineClobbers = CGF.getTarget().getClobbers();
+  std::string_view MachineClobbers = CGF.getTarget().getClobbers();
   if (!MachineClobbers.empty()) {
     Constraints += ',';
     Constraints += MachineClobbers;

clang/lib/CodeGen/CGStmt.cpp

@@ -2779,7 +2779,7 @@ void CodeGenFunction::EmitAsmStmt(const AsmStmt &S) {
          "unwind clobber can't be used with asm goto");
 
   // Add machine specific clobbers
-  std::string MachineClobbers = getTarget().getClobbers();
+  std::string_view MachineClobbers = getTarget().getClobbers();
   if (!MachineClobbers.empty()) {
     if (!Constraints.empty())
       Constraints += ',';