[Multilib] Add -fmultilib-flag command-line option

clang/include/clang/Driver/Multilib.h

@@ -101,6 +101,25 @@ class Multilib {
 
 raw_ostream &operator<<(raw_ostream &OS, const Multilib &M);
 
+namespace custom_flag {
+struct Declaration;
+using DeclarationPtr = std::shared_ptr<Declaration>;
+
+struct ValueDetail {
+  std::string Name;
+  std::optional<SmallVector<std::string>> MacroDefines;
+  DeclarationPtr Decl;
+};
+
+struct Declaration {
+  std::string Name;
+  SmallVector<ValueDetail> ValueList;
+  std::optional<size_t> DefaultValueIdx;
+};
+
+static constexpr StringRef Prefix = "-fmultilib-flag=";
+} // namespace custom_flag
+
 /// See also MultilibSetBuilder for combining multilibs into a set.
 class MultilibSet {
 public:
@@ -120,15 +139,18 @@ class MultilibSet {
 
 private:
   multilib_list Multilibs;
-  std::vector<FlagMatcher> FlagMatchers;
+  SmallVector<FlagMatcher> FlagMatchers;
+  SmallVector<custom_flag::DeclarationPtr> CustomFlagDecls;
   IncludeDirsFunc IncludeCallback;
   IncludeDirsFunc FilePathsCallback;
 
 public:
   MultilibSet() = default;
   MultilibSet(multilib_list &&Multilibs,
-              std::vector<FlagMatcher> &&FlagMatchers = {})
-      : Multilibs(Multilibs), FlagMatchers(FlagMatchers) {}
+              SmallVector<FlagMatcher> &&FlagMatchers = {},
+              SmallVector<custom_flag::DeclarationPtr> &&CustomFlagDecls = {})
+      : Multilibs(std::move(Multilibs)), FlagMatchers(std::move(FlagMatchers)),
+        CustomFlagDecls(std::move(CustomFlagDecls)) {}
 
   const multilib_list &getMultilibs() { return Multilibs; }
 

clang/include/clang/Driver/Options.td

@@ -5721,6 +5721,8 @@ def print_multi_directory : Flag<["-", "--"], "print-multi-directory">;
 def print_multi_lib : Flag<["-", "--"], "print-multi-lib">;
 def print_multi_flags : Flag<["-", "--"], "print-multi-flags-experimental">,
   HelpText<"Print the flags used for selecting multilibs (experimental)">;
+def fmultilib_flag : Joined<["-", "--"], "fmultilib-flag=">,
+  Visibility<[ClangOption]>;
 def print_multi_os_directory : Flag<["-", "--"], "print-multi-os-directory">,
   Flags<[Unsupported]>;
 def print_target_triple : Flag<["-", "--"], "print-target-triple">,

clang/lib/Driver/Multilib.cpp

@@ -10,6 +10,7 @@
 #include "clang/Basic/LLVM.h"
 #include "clang/Driver/Driver.h"
 #include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -201,13 +202,20 @@ struct MultilibGroupSerialization {
 
 struct MultilibSetSerialization {
   llvm::VersionTuple MultilibVersion;
-  std::vector<MultilibGroupSerialization> Groups;
-  std::vector<MultilibSerialization> Multilibs;
-  std::vector<MultilibSet::FlagMatcher> FlagMatchers;
+  SmallVector<MultilibGroupSerialization> Groups;
+  SmallVector<MultilibSerialization> Multilibs;
+  SmallVector<MultilibSet::FlagMatcher> FlagMatchers;
+  SmallVector<custom_flag::DeclarationPtr> CustomFlagDeclarations;
 };
 
 } // end anonymous namespace
 
+LLVM_YAML_IS_SEQUENCE_VECTOR(MultilibSerialization)
+LLVM_YAML_IS_SEQUENCE_VECTOR(MultilibGroupSerialization)
+LLVM_YAML_IS_SEQUENCE_VECTOR(MultilibSet::FlagMatcher)
+LLVM_YAML_IS_SEQUENCE_VECTOR(custom_flag::ValueDetail)
+LLVM_YAML_IS_SEQUENCE_VECTOR(custom_flag::DeclarationPtr)
+
 template <> struct llvm::yaml::MappingTraits<MultilibSerialization> {
   static void mapping(llvm::yaml::IO &io, MultilibSerialization &V) {
     io.mapOptional("Dir", V.Dir);
@@ -255,11 +263,63 @@ template <> struct llvm::yaml::MappingTraits<MultilibSet::FlagMatcher> {
   }
 };
 
+template <>
+struct llvm::yaml::MappingContextTraits<custom_flag::ValueDetail,
+                                        llvm::SmallSet<std::string, 32>> {
+  static void mapping(llvm::yaml::IO &io, custom_flag::ValueDetail &V,
+                      llvm::SmallSet<std::string, 32> &) {
+    io.mapRequired("Name", V.Name);
+    io.mapOptional("MacroDefines", V.MacroDefines);
+  }
+  static std::string validate(IO &io, custom_flag::ValueDetail &V,
+                              llvm::SmallSet<std::string, 32> &NameSet) {
+    if (V.Name.empty())
+      return "custom flag value requires a name";
+    if (!NameSet.insert(V.Name).second)
+      return "duplicate custom flag value name: \"" + V.Name + "\"";
+    return {};
+  }
+};
+
+template <>
+struct llvm::yaml::MappingContextTraits<custom_flag::DeclarationPtr,
+                                        llvm::SmallSet<std::string, 32>> {
+  static void mapping(llvm::yaml::IO &io, custom_flag::DeclarationPtr &V,
+                      llvm::SmallSet<std::string, 32> &NameSet) {
+    assert(!V);
+    V = std::make_shared<custom_flag::Declaration>();
+    io.mapRequired("Name", V->Name);
+    io.mapRequired("Values", V->ValueList, NameSet);
+    std::string DefaultValueName;
+    io.mapRequired("Default", DefaultValueName);
+
+    for (auto [Idx, Value] : llvm::enumerate(V->ValueList)) {
+      Value.Decl = V;
+      if (Value.Name == DefaultValueName) {
+        assert(!V->DefaultValueIdx);
+        V->DefaultValueIdx = Idx;
+      }
+    }
+  }
+  static std::string validate(IO &io, custom_flag::DeclarationPtr &V,
+                              llvm::SmallSet<std::string, 32> &) {
+    if (V->Name.empty())
+      return "custom flag requires a name";
+    if (V->ValueList.empty())
+      return "custom flag must have at least one value";
+    if (!V->DefaultValueIdx)
+      return "custom flag must have a default value";
+    return {};
+  }
+};
+
 template <> struct llvm::yaml::MappingTraits<MultilibSetSerialization> {
   static void mapping(llvm::yaml::IO &io, MultilibSetSerialization &M) {
     io.mapRequired("MultilibVersion", M.MultilibVersion);
     io.mapRequired("Variants", M.Multilibs);
     io.mapOptional("Groups", M.Groups);
+    llvm::SmallSet<std::string, 32> NameSet;
+    io.mapOptionalWithContext("Flags", M.CustomFlagDeclarations, NameSet);
     io.mapOptional("Mappings", M.FlagMatchers);
   }
   static std::string validate(IO &io, MultilibSetSerialization &M) {
@@ -288,10 +348,6 @@ template <> struct llvm::yaml::MappingTraits<MultilibSetSerialization> {
   }
 };
 
-LLVM_YAML_IS_SEQUENCE_VECTOR(MultilibSerialization)
-LLVM_YAML_IS_SEQUENCE_VECTOR(MultilibGroupSerialization)
-LLVM_YAML_IS_SEQUENCE_VECTOR(MultilibSet::FlagMatcher)
-
 llvm::ErrorOr<MultilibSet>
 MultilibSet::parseYaml(llvm::MemoryBufferRef Input,
                        llvm::SourceMgr::DiagHandlerTy DiagHandler,
@@ -319,7 +375,8 @@ MultilibSet::parseYaml(llvm::MemoryBufferRef Input,
     }
   }
 
-  return MultilibSet(std::move(Multilibs), std::move(MS.FlagMatchers));
+  return MultilibSet(std::move(Multilibs), std::move(MS.FlagMatchers),
+                     std::move(MS.CustomFlagDeclarations));
 }
 
 LLVM_DUMP_METHOD void MultilibSet::dump() const {

clang/lib/Driver/ToolChain.cpp

@@ -196,6 +196,15 @@ bool ToolChain::defaultToIEEELongDouble() const {
   return PPC_LINUX_DEFAULT_IEEELONGDOUBLE && getTriple().isOSLinux();
 }
 
+static void processMultilibCustomFlags(Multilib::flags_list &List,
+                                       const llvm::opt::ArgList &Args) {
+  for (const Arg *MultilibFlagArg :
+       Args.filtered(options::OPT_fmultilib_flag)) {
+    List.push_back(MultilibFlagArg->getAsString(Args));
+    MultilibFlagArg->claim();
+  }
+}
+
 static void getAArch64MultilibFlags(const Driver &D,
                                           const llvm::Triple &Triple,
                                           const llvm::opt::ArgList &Args,
@@ -246,6 +255,8 @@ static void getAArch64MultilibFlags(const Driver &D,
   if (ABIArg) {
     Result.push_back(ABIArg->getAsString(Args));
   }
+
+  processMultilibCustomFlags(Result, Args);
 }
 
 static void getARMMultilibFlags(const Driver &D,
@@ -313,6 +324,7 @@ static void getARMMultilibFlags(const Driver &D,
     if (Endian->getOption().matches(options::OPT_mbig_endian))
       Result.push_back(Endian->getAsString(Args));
   }
+  processMultilibCustomFlags(Result, Args);
 }
 
 static void getRISCVMultilibFlags(const Driver &D, const llvm::Triple &Triple,

clang/test/Driver/baremetal-multilib-custom-flags-parsing.yaml

@@ -0,0 +1,133 @@
+# RUN: split-file %s %t
+
+# RUN: %clang --target=arm-none-eabi --multi-lib-config=%t/multilib-without-macro-defines.yaml %s -### -o /dev/null 2>&1 \
+# RUN: | FileCheck %s
+# RUN: %clang --target=arm-none-eabi --multi-lib-config=%t/multilib-with-macro-defines.yaml %s -### -o /dev/null 2>&1 \
+# RUN: | FileCheck %s
+# CHECK-NOT: error:
+
+# RUN: %clang --target=arm-none-eabi --multi-lib-config=%t/missing-flag-name.yaml %s -### -o /dev/null 2>&1 \
+# RUN: | FileCheck %s --check-prefix=CHECK-MISSING-FLAG-NAME
+# CHECK-MISSING-FLAG-NAME: error: custom flag requires a name
+
+# RUN: %clang --target=arm-none-eabi --multi-lib-config=%t/missing-flag-values.yaml %s -### -o /dev/null 2>&1 \
+# RUN: | FileCheck %s --check-prefix=CHECK-MISSING-FLAG-VALUES
+# CHECK-MISSING-FLAG-VALUES: error: custom flag must have at least one value
+
+# RUN: %clang --target=arm-none-eabi --multi-lib-config=%t/missing-flag-value-default.yaml %s -### -o /dev/null 2>&1 \
+# RUN: | FileCheck %s --check-prefix=CHECK-MISSING-FLAG-VALUE-DEFAULT
+# CHECK-MISSING-FLAG-VALUE-DEFAULT: error: custom flag must have a default value
+
+# RUN: %clang --target=arm-none-eabi --multi-lib-config=%t/missing-flag-value-name.yaml %s -### -o /dev/null 2>&1 \
+# RUN: | FileCheck %s --check-prefix=CHECK-MISSING-FLAG-VALUE-NAME
+# CHECK-MISSING-FLAG-VALUE-NAME: error: custom flag value requires a name
+
+# RUN: %clang --target=arm-none-eabi --multi-lib-config=%t/duplicate-flag-value-name.yaml %s -### -o /dev/null 2>&1 \
+# RUN: | FileCheck %s --check-prefix=CHECK-DUPLICATE-FLAG-VALUE-NAME
+# CHECK-DUPLICATE-FLAG-VALUE-NAME:      error: duplicate custom flag value name: "value-name"
+# CHECK-DUPLICATE-FLAG-VALUE-NAME-NEXT: - Name: value-name
+
+#--- multilib-without-macro-defines.yaml
+---
+MultilibVersion: 1.0
+
+Variants:
+- Dir: libc
+  Flags: [-fmultilib-flag=a]
+
+Flags:
+  - Name: flag
+    Values:
+    - Name: a
+    - Name: b
+    Default: a
+
+#--- multilib-with-macro-defines.yaml
+---
+MultilibVersion: 1.0
+
+Variants:
+- Dir: libc
+  Flags: [-fmultilib-flag=a]
+
+Flags:
+  - Name: flag
+    Values:
+    - Name: a
+      MacroDefines: [FEATURE_A]
+    - Name: b
+      MacroDefines: [FEATURE_B]
+    Default: a
+
+#--- missing-flag-name.yaml
+---
+MultilibVersion: 1.0
+
+Variants:
+- Dir: libc
+  Flags: [-fmultilib-flag=a]
+
+Flags:
+  - Values:
+    - Name: a
+    Default: a
+
+#--- missing-flag-values.yaml
+---
+MultilibVersion: 1.0
+
+Variants:
+- Dir: libc
+  Flags: [-fmultilib-flag=a]
+
+Flags:
+  - Name: flag
+    Values:
+    Default: a
+
+#--- missing-flag-value-default.yaml
+---
+MultilibVersion: 1.0
+
+Variants:
+- Dir: libc
+  Flags: [-fmultilib-flag=a]
+
+Flags:
+  - Name: flag
+    Values:
+    - Name: a
+    Default:
+
+#--- missing-flag-value-name.yaml
+---
+MultilibVersion: 1.0
+
+Variants:
+- Dir: libc
+  Flags: [-fmultilib-flag=a]
+
+Flags:
+  - Name: flag
+    Values:
+    - Name:
+    Default: a
+
+#--- duplicate-flag-value-name.yaml
+---
+MultilibVersion: 1.0
+
+Variants:
+- Dir: libc
+  Flags: [-fmultilib-flag=value-name]
+
+Flags:
+  - Name: a
+    Values:
+    - Name: value-name
+    - Name: value-a
+    Default: value-name
+  - Name: b
+    Values:
+    - Name: value-name
+    Default: value-name

clang/test/Driver/print-multi-selection-flags.c

@@ -90,3 +90,10 @@
 // CHECK-RV32E-ORDER: --target=riscv32-unknown-none-elf
 // CHECK-RV32E-ORDER: -mabi=ilp32e
 // CHECK-RV32E-ORDER: -march=rv32e{{[0-9]+p[0-9]+}}_c{{[0-9]+p[0-9]+}}_zicsr{{[0-9]+p[0-9]+}}
+
+// RUN: %clang -print-multi-flags-experimental --target=armv8m.main-none-eabi -fmultilib-flag=foo -fmultilib-flag=bar | FileCheck --check-prefixes=CHECK-MULTILIB-CUSTOM-FLAG,CHECK-ARM-MULTILIB-CUSTOM-FLAG %s
+// RUN: %clang -print-multi-flags-experimental --target=aarch64-none-eabi     -fmultilib-flag=foo -fmultilib-flag=bar | FileCheck --check-prefixes=CHECK-MULTILIB-CUSTOM-FLAG,CHECK-AARCH64-MULTILIB-CUSTOM-FLAG %s
+// CHECK-ARM-MULTILIB-CUSTOM-FLAG:     --target=thumbv8m.main-unknown-none-eabi
+// CHECK-AARCH64-MULTILIB-CUSTOM-FLAG: --target=aarch64-unknown-none-eabi
+// CHECK-MULTILIB-CUSTOM-FLAG-DAG:     -fmultilib-flag=foo
+// CHECK-MULTILIB-CUSTOM-FLAG-DAG:     -fmultilib-flag=bar