[Clang][Driver] Add option to provide path for multilib's YAML config file

clang/include/clang/Driver/Options.td

@@ -5558,6 +5558,9 @@ def mthumb : Flag<["-"], "mthumb">, Group<m_Group>;
 def mtune_EQ : Joined<["-"], "mtune=">, Group<m_Group>,
   Visibility<[ClangOption, FlangOption]>,
   HelpText<"Only supported on AArch64, PowerPC, RISC-V, SPARC, SystemZ, and X86">;
+def multi_lib_config : Joined<["-", "--"], "multi-lib-config=">,
+  HelpText<"Path to the YAML configuration file to be used for multilib selection">,
+  MetaVarName<"<file>">;
 def multi__module : Flag<["-"], "multi_module">;
 def multiply__defined__unused : Separate<["-"], "multiply_defined_unused">;
 def multiply__defined : Separate<["-"], "multiply_defined">;

clang/lib/Driver/ToolChains/BareMetal.cpp

@@ -97,9 +97,23 @@ static bool findRISCVMultilibs(const Driver &D,
   return false;
 }
 
+static std::string computeBaseSysRoot(const Driver &D, bool IncludeTriple) {
+  if (!D.SysRoot.empty())
+    return D.SysRoot;
+
+  SmallString<128> SysRootDir(D.Dir);
+  llvm::sys::path::append(SysRootDir, "..", "lib", "clang-runtimes");
+
+  if (IncludeTriple)
+    llvm::sys::path::append(SysRootDir, D.getTargetTriple());
+
+  return std::string(SysRootDir);
+}
+
 BareMetal::BareMetal(const Driver &D, const llvm::Triple &Triple,
                      const ArgList &Args)
-    : ToolChain(D, Triple, Args) {
+    : ToolChain(D, Triple, Args),
+      SysRoot(computeBaseSysRoot(D, /*IncludeTriple=*/true)) {
   getProgramPaths().push_back(getDriver().Dir);
 
   findMultilibs(D, Triple, Args);
@@ -194,37 +208,37 @@ static void findMultilibsFromYAML(const ToolChain &TC, const Driver &D,
 
 static constexpr llvm::StringLiteral MultilibFilename = "multilib.yaml";
 
-// Get the sysroot, before multilib takes effect.
-static std::string computeBaseSysRoot(const Driver &D,
-                                      const llvm::Triple &Triple) {
-  if (!D.SysRoot.empty())
-    return D.SysRoot;
-
-  SmallString<128> SysRootDir(D.Dir);
-  llvm::sys::path::append(SysRootDir, "..", "lib", "clang-runtimes");
-
-  SmallString<128> MultilibPath(SysRootDir);
-  llvm::sys::path::append(MultilibPath, MultilibFilename);
-
-  // New behaviour: if multilib.yaml is found then use clang-runtimes as the
-  // sysroot.
-  if (D.getVFS().exists(MultilibPath))
-    return std::string(SysRootDir);
-
-  // Otherwise fall back to the old behaviour of appending the target triple.
-  llvm::sys::path::append(SysRootDir, D.getTargetTriple());
-  return std::string(SysRootDir);
+static std::optional<llvm::SmallString<128>>
+getMultilibConfigPath(const Driver &D, const llvm::Triple &Triple,
+                      const ArgList &Args) {
+  llvm::SmallString<128> MultilibPath;
+  if (Arg *ConfigFileArg = Args.getLastArg(options::OPT_multi_lib_config)) {
+    MultilibPath = ConfigFileArg->getValue();
+    if (!D.getVFS().exists(MultilibPath)) {
+      D.Diag(clang::diag::err_drv_no_such_file) << MultilibPath.str();
+      return {};
+    }
+  } else {
+    MultilibPath = computeBaseSysRoot(D, /*IncludeTriple=*/false);
+    llvm::sys::path::append(MultilibPath, MultilibFilename);
+  }
+  return MultilibPath;
 }
 
 void BareMetal::findMultilibs(const Driver &D, const llvm::Triple &Triple,
                               const ArgList &Args) {
   DetectedMultilibs Result;
   // Look for a multilib.yaml before trying target-specific hardwired logic.
   // If it exists, always do what it specifies.
-  llvm::SmallString<128> MultilibPath(computeBaseSysRoot(D, Triple));
-  llvm::sys::path::append(MultilibPath, MultilibFilename);
-  if (D.getVFS().exists(MultilibPath)) {
-    findMultilibsFromYAML(*this, D, MultilibPath, Args, Result);
+  std::optional<llvm::SmallString<128>> MultilibPath =
+      getMultilibConfigPath(D, Triple, Args);
+  if (!MultilibPath)
+    return;
+  if (D.getVFS().exists(*MultilibPath)) {
+    // If multilib.yaml is found, update sysroot so it doesn't use a target
+    // specific suffix
+    SysRoot = computeBaseSysRoot(D, /*IncludeTriple=*/false);
+    findMultilibsFromYAML(*this, D, *MultilibPath, Args, Result);
     SelectedMultilibs = Result.SelectedMultilibs;
     Multilibs = Result.Multilibs;
   } else if (isRISCVBareMetal(Triple)) {
@@ -248,9 +262,7 @@ Tool *BareMetal::buildStaticLibTool() const {
   return new tools::baremetal::StaticLibTool(*this);
 }
 
-std::string BareMetal::computeSysRoot() const {
-  return computeBaseSysRoot(getDriver(), getTriple());
-}
+std::string BareMetal::computeSysRoot() const { return SysRoot; }
 
 BareMetal::OrderedMultilibs BareMetal::getOrderedMultilibs() const {
   // Get multilibs in reverse order because they're ordered most-specific last.

clang/lib/Driver/ToolChains/BareMetal.h

@@ -78,6 +78,8 @@ class LLVM_LIBRARY_VISIBILITY BareMetal : public ToolChain {
   using OrderedMultilibs =
       llvm::iterator_range<llvm::SmallVector<Multilib>::const_reverse_iterator>;
   OrderedMultilibs getOrderedMultilibs() const;
+
+  std::string SysRoot;
 };
 
 } // namespace toolchains

clang/test/Driver/Inputs/multilib/empty.yaml

@@ -0,0 +1,8 @@
+
+MultilibVersion: 1.0
+
+Variants:
+
+Mappings:
+
+...

clang/test/Driver/baremetal-multilib-custom-error.yaml

@@ -1,35 +1,28 @@
 # REQUIRES: shell
 # UNSUPPORTED: system-windows
 
-# RUN: rm -rf %t
-# RUN: mkdir -p %t/bin
-# RUN: mkdir -p %t/lib/clang-runtimes/arm-none-eabi/thumb/v8-m.main/fp/lib
-# RUN: touch %t/lib/clang-runtimes/arm-none-eabi/thumb/v8-m.main/fp/lib/libclang_rt.builtins.a
-# RUN: ln -s %clang %t/bin/clang
-# RUN: ln -s %s %t/lib/clang-runtimes/multilib.yaml
-
-# RUN: %t/bin/clang -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
 # RUN:     --target=thumbv8m.main-none-eabi -march=armv8.1m.main --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-PRINT-MULTI-DIRECTORY-NOMVE-SOFTFLOAT %s
 # CHECK-PRINT-MULTI-DIRECTORY-NOMVE-SOFTFLOAT: nomve-softfloat
 
-# RUN: not %t/bin/clang -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: not %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
 # RUN:     --target=thumbv8m.main-none-eabi -march=armv8.1m.main+mve --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-ERROR %s
 # CHECK-ERROR: multilib configuration error: mve-softfloat is not supported
 
-# RUN: %t/bin/clang -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
 # RUN:     --target=thumbv8m.main-none-eabi -march=armv8.1m.main+mve -mfloat-abi=hard --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-PRINT-MULTI-DIRECTORY-MVE-HARDFLOAT %s
 # CHECK-PRINT-MULTI-DIRECTORY-MVE-HARDFLOAT: mve-hardfloat
 
-# RUN: %t/bin/clang -no-canonical-prefixes -print-multi-lib 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-lib 2>&1 \
 # RUN:     --target=arm-none-eabi --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-PRINT-MULTI-LIB %s
 # CHECK-PRINT-MULTI-LIB: nomve-softfloat;@-target=thumbv8.1m.main-unknown-none-eabi
 # CHECK-PRINT-MULTI-LIB-NEXT: mve-hardfloat;@-target=thumbv8.1m.main-unknown-none-eabihf@march=thumbv8.1m.main+mve@mfloat-abi=hard
 
-# RUN: %t/bin/clang -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
 # RUN:     --target=arm-none-eabi --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-NO-MATCH-WARNING %s
 # CHECK-NO-MATCH-WARNING: clang: note: available multilibs are:

clang/test/Driver/baremetal-multilib-exclusive-group.yaml

@@ -1,17 +1,9 @@
 # UNSUPPORTED: system-windows
 
-# RUN: rm -rf %t
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c++ %s -### -o %t.out --target=thumbv7em-none-unknown-eabi --sysroot= 2>%t.err
 
-# RUN: mkdir -p %t/baremetal_multilib/bin
-# RUN: ln -s %clang %t/baremetal_multilib/bin/clang
-
-# RUN: mkdir -p %t/baremetal_multilib/lib/clang-runtimes
-# RUN: ln -s %s %t/baremetal_multilib/lib/clang-runtimes/multilib.yaml
-
-# RUN: %t/baremetal_multilib/bin/clang -no-canonical-prefixes -x c++ %s -### -o %t.out --target=thumbv7em-none-unknown-eabi --sysroot= 2>%t.err
-
-# RUN: FileCheck -DSYSROOT=%t/baremetal_multilib %s < %t.err --check-prefix=POS
-# RUN: FileCheck -DSYSROOT=%t/baremetal_multilib %s < %t.err --check-prefix=NEG
+# RUN: FileCheck %s < %t.err --check-prefix=POS
+# RUN: FileCheck %s < %t.err --check-prefix=NEG
 
 # Expected results:
 #
@@ -25,14 +17,14 @@
 # So we expect five of these seven directories to show up in the clang-cc1
 # command line, but not testdir1_exclusive or testdir2_exclusive.
 
-# POS-DAG: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/testdir1_non_exclusive/include/c++/v1"
+# POS-DAG: "-internal-isystem" "[[SYSROOT:[^"]*]]/bin/../lib/clang-runtimes/testdir1_non_exclusive/include/c++/v1"
 # POS-DAG: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/testdir2_non_exclusive/include/c++/v1"
 # POS-DAG: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/testdir3_exclusive/include/c++/v1"
 # POS-DAG: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/testdir1_own_group/include/c++/v1"
 # POS-DAG: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/testdir2_own_group/include/c++/v1"
 
-# NEG-NOT: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/testdir1_exclusive/include/c++/v1"
-# NEG-NOT: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/testdir2_exclusive/include/c++/v1"
+# NEG-NOT: "-internal-isystem" "{{[^"]*}}/bin/../lib/clang-runtimes/testdir1_exclusive/include/c++/v1"
+# NEG-NOT: "-internal-isystem" "{{[^"]*}}/bin/../lib/clang-runtimes/testdir2_exclusive/include/c++/v1"
 
 ---
 MultilibVersion: 1.0

clang/test/Driver/baremetal-multilib-group-error.yaml

@@ -1,14 +1,6 @@
 # UNSUPPORTED: system-windows
 
-# RUN: rm -rf %t
-
-# RUN: mkdir -p %t/baremetal_multilib/bin
-# RUN: ln -s %clang %t/baremetal_multilib/bin/clang
-
-# RUN: mkdir -p %t/baremetal_multilib/lib/clang-runtimes
-# RUN: ln -s %s %t/baremetal_multilib/lib/clang-runtimes/multilib.yaml
-
-# RUN: %t/baremetal_multilib/bin/clang -no-canonical-prefixes -x c++ %s -### -o %t.out --target=thumbv7em-none-unknown-eabi --sysroot= 2>%t.err
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c++ %s -### -o %t.out --target=thumbv7em-none-unknown-eabi --sysroot= 2>%t.err
 # RUN: FileCheck %s < %t.err
 
 ---

clang/test/Driver/baremetal-multilib-layered.yaml

@@ -9,24 +9,18 @@
 # However -fno-exceptions is not yet supported for multilib selection
 # so we use a more contrived -mfloat-abi example instead.
 
-# RUN: rm -rf %T/baremetal_multilib_layered
-# RUN: mkdir -p %T/baremetal_multilib_layered/bin
-# RUN: mkdir -p %T/baremetal_multilib_layered/lib/clang-runtimes
-# RUN: ln -s %clang %T/baremetal_multilib_layered/bin/clang
-# RUN: ln -s %s %T/baremetal_multilib_layered/lib/clang-runtimes/multilib.yaml
-
-# RUN: %T/baremetal_multilib_layered/bin/clang -no-canonical-prefixes -x c++ %s -### -o %t.out 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c++ %s -### -o %t.out 2>&1 \
 # RUN:     --target=thumbv7m-none-eabi -mfloat-abi=softfp --sysroot= \
-# RUN:   | FileCheck -DSYSROOT=%T/baremetal_multilib_layered %s
+# RUN:   | FileCheck %s
 # CHECK:      "-cc1" "-triple" "thumbv7m-unknown-none-eabi"
-# CHECK-SAME: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/softfp/include/c++/v1"
+# CHECK-SAME: "-internal-isystem" "[[SYSROOT:[^"]*]]/bin/../lib/clang-runtimes/softfp/include/c++/v1"
 # CHECK-SAME: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/soft/include/c++/v1"
 # CHECK-SAME: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/softfp/include"
 # CHECK-SAME: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/soft/include"
 # CHECK-NEXT: "-L[[SYSROOT]]/bin/../lib/clang-runtimes/softfp/lib"
 # CHECK-SAME: "-L[[SYSROOT]]/bin/../lib/clang-runtimes/soft/lib"
 
-# RUN: %T/baremetal_multilib_layered/bin/clang -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
 # RUN:     --target=arm-none-eabi -mfloat-abi=softfp --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-PRINT-MULTI-DIRECTORY %s
 # CHECK-PRINT-MULTI-DIRECTORY:      soft

clang/test/Driver/baremetal-multilib.yaml

@@ -1,26 +1,19 @@
 # REQUIRES: shell
 # UNSUPPORTED: system-windows
 
-# RUN: rm -rf %T/baremetal_multilib
-# RUN: mkdir -p %T/baremetal_multilib/bin
-# RUN: mkdir -p %T/baremetal_multilib/lib/clang-runtimes/arm-none-eabi/thumb/v8-m.main/fp/lib
-# RUN: touch %T/baremetal_multilib/lib/clang-runtimes/arm-none-eabi/thumb/v8-m.main/fp/lib/libclang_rt.builtins.a
-# RUN: ln -s %clang %T/baremetal_multilib/bin/clang
-# RUN: ln -s %s %T/baremetal_multilib/lib/clang-runtimes/multilib.yaml
-
-# RUN: %T/baremetal_multilib/bin/clang -no-canonical-prefixes -x c++ %s -### -o %t.out 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c++ %s -### -o %t.out 2>&1 \
 # RUN:     --target=thumbv8m.main-none-eabihf --sysroot= \
-# RUN:   | FileCheck -DSYSROOT=%T/baremetal_multilib %s
+# RUN:   | FileCheck %s
 # CHECK:      "-cc1" "-triple" "thumbv8m.main-unknown-none-eabihf"
-# CHECK-SAME: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/arm-none-eabi/thumb/v8-m.main/fp/include/c++/v1"
+# CHECK-SAME: "-internal-isystem" "[[SYSROOT:[^"]*]]/bin/../lib/clang-runtimes/arm-none-eabi/thumb/v8-m.main/fp/include/c++/v1"
 # CHECK-SAME: "-internal-isystem" "[[SYSROOT]]/bin/../lib/clang-runtimes/arm-none-eabi/thumb/v8-m.main/fp/include"
 # CHECK-SAME: "-x" "c++" "{{.*}}baremetal-multilib.yaml"
 # CHECK-NEXT: ld{{(.exe)?}}" "{{.*}}.o" "-Bstatic"
 # CHECK-SAME: "-L[[SYSROOT]]/bin/../lib/clang-runtimes/arm-none-eabi/thumb/v8-m.main/fp/lib"
 # CHECK-SAME: "-lc" "-lm" "{{[^"]*}}libclang_rt.builtins.a"
 # CHECK-SAME: "-o" "{{.*}}.tmp.out"
 
-# RUN: %T/baremetal_multilib/bin/clang -no-canonical-prefixes -x c++ %s -### -o %t.out 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x c++ %s -### -o %t.out 2>&1 \
 # RUN:     --target=thumbv7em-none-eabi -mfpu=fpv4-sp-d16 --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-NO-MATCH %s
 # CHECK-NO-MATCH: warning: no multilib found matching flags:
@@ -30,12 +23,12 @@
 # CHECK-NO-MATCH: --target=thumbv7m-unknown-none-eabi -mfpu=none
 # CHECK-NO-MATCH: --target=thumbv7em-unknown-none-eabi -mfpu=none
 
-# RUN: %T/baremetal_multilib/bin/clang -no-canonical-prefixes -print-multi-directory 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-directory 2>&1 \
 # RUN:     --target=thumbv8m.main-none-eabihf --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-PRINT-MULTI-DIRECTORY %s
 # CHECK-PRINT-MULTI-DIRECTORY: arm-none-eabi/thumb/v8-m.main/fp
 
-# RUN: %T/baremetal_multilib/bin/clang -no-canonical-prefixes -print-multi-lib 2>&1 \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -print-multi-lib 2>&1 \
 # RUN:     --target=arm-none-eabi --sysroot= \
 # RUN:   | FileCheck --check-prefix=CHECK-PRINT-MULTI-LIB %s
 # CHECK-PRINT-MULTI-LIB: arm-none-eabi/thumb/v6-m/nofp;@-target=thumbv6m-unknown-none-eabi@mfpu=none
@@ -49,7 +42,7 @@
 # CHECK-PRINT-MULTI-LIB: arm-none-eabi/thumb/v8.1-m.main/fp;@-target=thumbv8.1m.main-unknown-none-eabihf@mfpu=fp-armv8-fullfp16-sp-d16
 # CHECK-PRINT-MULTI-LIB: arm-none-eabi/thumb/v8.1-m.main/nofp/mve;@-target=thumbv8.1m.main-unknown-none-eabihf@march=thumbv8.1m.main+mve@mfpu=none
 
-# RUN: %T/baremetal_multilib/bin/clang -no-canonical-prefixes -x assembler -mexecute-only \
+# RUN: %clang --multi-lib-config=%s -no-canonical-prefixes -x assembler -mexecute-only \
 # RUN:     --target=arm-none-eabi --sysroot= %s -c -### 2>&1 \
 # RUN:    | FileCheck %s --check-prefix=CHECK-NO-EXECUTE-ONLY-ASM
 # CHECK-NO-EXECUTE-ONLY-ASM: warning: argument unused during compilation: '-mexecute-only'