Add basic aarch64-none-elf bare metal driver.

[peter.smith]

LGTM thanks for the update. This looks like it follows the same format as the other <arch>-none-elf toolchains, and AArch64 can benefit from the bare-metal driver for easier access to LLD. Will be worth waiting a few days to see if there is any other feedback.

[MaskRay]

clang/lib/Driver/ToolChains/BareMetal.cpp

133

Is vendor check necessary?

clang/test/Driver/baremetal.cpp

105

You may follow the style in linux-cross.cpp and enumerate include paths.

[kristof.beyls]

Updated test based on feedback from @MaskRay

clang/lib/Driver/ToolChains/BareMetal.cpp

133

I'm guessing that without the vendor check, triples aarch64-anything-elf would also be considered bare metal triples?
Or would it be aarch64-none-anything-elf?
I'm afraid I don't know the answer to the question on whether the vendor check should be removed or not.

However, I think it's best for this patch to keep this as is to keep consistency with the arm and riscv bare metal targets in this file, which also have the same check for the triple vendor to be UnknownVendor.

If it would be best to drop this check, it probably would be best to do it as a separate patch, and potentially make the change for the arm and riscv triples too?

[kristof.beyls]

run clang-format on the patch.

[kristof.beyls]

@MaskRay - gentle ping: I wonder if you have any further remarks after I updated the patch based on your earlier feedback?

clang/lib/Driver/ToolChains/BareMetal.cpp

static bool isARMBareMetal(const llvm::Triple &Triple) {
 
   if (Triple.getEnvironment() != llvm::Triple::EABI &&
       Triple.getEnvironment() != llvm::Triple::EABIHF)
     return false;
 
   return true;
 }
 
+/// Is the triple aarch64-none-elf?
+static bool isAArch64BareMetal(const llvm::Triple &Triple) {
+  if (Triple.getArch() != llvm::Triple::aarch64)
+    return false;
+
+  if (Triple.getVendor() != llvm::Triple::UnknownVendor)
+    return false;
+
+  if (Triple.getOS() != llvm::Triple::UnknownOS)
+    return false;
+
+  return Triple.getEnvironmentName() == "elf";
+}
+
 static bool isRISCVBareMetal(const llvm::Triple &Triple) {
   if (Triple.getArch() != llvm::Triple::riscv32 &&
       Triple.getArch() != llvm::Triple::riscv64)
     return false;
 
   if (Triple.getVendor() != llvm::Triple::UnknownVendor)
     return false;
 
if (isRISCVBareMetal(Triple)) {
     if (findRISCVMultilibs(D, Triple, Args, Result)) {
       SelectedMultilib = Result.SelectedMultilib;
       Multilibs = Result.Multilibs;
     }
   }
 }
 
 bool BareMetal::handlesTarget(const llvm::Triple &Triple) {
-  return isARMBareMetal(Triple) || isRISCVBareMetal(Triple);
+  return isARMBareMetal(Triple) || isAArch64BareMetal(Triple) ||
+         isRISCVBareMetal(Triple);
 }
 
 Tool *BareMetal::buildLinker() const {
   return new tools::baremetal::Linker(*this);
 }
 
 std::string BareMetal::getCompilerRTPath() const { return getRuntimesDir(); }
 

clang/test/Driver/baremetal.cpp

 // RUN: %clang -### -target arm-none-eabi -rtlib=libgcc -v %s 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-RTLIB-GCC
 // CHECK-RTLIB-GCC: -lgcc
 
 // RUN: %clang -### -target arm-none-eabi -v %s 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=CHECK-SYSROOT-INC
 // CHECK-SYSROOT-INC-NOT: "-internal-isystem" "include"
 
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+// RUN:      -target aarch64-none-elf \
+// RUN:   | FileCheck --check-prefix=CHECK-AARCH64-NO-HOST-INC %s
+// Verify that the bare metal driver does not include any host system paths:
+// CHECK-AARCH64-NO-HOST-INC: InstalledDir: [[INSTALLEDDIR:.+]]
+// CHECK-AARCH64-NO-HOST-INC: "-resource-dir" "[[RESOURCE:[^"]+]]"
+// CHECK-AARCH64-NO-HOST-INC-SAME: "-internal-isystem" "[[INSTALLEDDIR]]/../lib/clang-runtimes/aarch64-none-elf/include/c++/v1"
+// CHECK-AARCH64-NO-HOST-INC-SAME: "-internal-isystem" "[[RESOURCE]]/include"
+// CHECK-AARCH64-NO-HOST-INC-SAME: "-internal-isystem" "[[INSTALLEDDIR]]/../lib/clang-runtimes/aarch64-none-elf/include"
+
+// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     -target riscv64-unknown-elf \
 // RUN:     -L some/directory/user/asked/for \
 // RUN:     --sysroot=%S/Inputs/basic_riscv64_tree/riscv64-unknown-elf \
 // RUN:   | FileCheck --check-prefix=CHECK-RV64 %s
 // CHECK-RV64: "[[PREFIX_DIR:.*]]{{[/\\]+}}{{[^/^\\]+}}{{[/\\]+}}clang{{.*}}" "-cc1" "-triple" "riscv64-unknown-unknown-elf"
 // CHECK-RV64-SAME: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // CHECK-RV64-SAME: "-isysroot" "[[SYSROOT:[^"]*]]"
 // CHECK-RV64-SAME: "-internal-isystem" "[[SYSROOT]]{{[/\\]+}}include{{[/\\]+}}c++{{[/\\]+}}v1"

clang/test/Driver/gcc_forward.c

-// RUN: %clang -### %s -target aarch64-none-elf \
+// RUN: %clang -### %s -target x86-none-elf \
 // RUN:   --coverage -e _start -fuse-ld=lld --ld-path=ld -nostartfiles \
 // RUN:   -nostdlib -r -rdynamic -specs=nosys.specs -static -static-pie \
 // RUN:   2>&1 | FileCheck --check-prefix=FORWARD %s
 // FORWARD: gcc{{[^"]*}}" "--coverage" "-fuse-ld=lld" "--ld-path=ld" "-nostartfiles" "-nostdlib" "-rdynamic" "-specs=nosys.specs" "-static" "-static-pie" "-o" "a.out" "{{.*}}.o" "-e" "_start" "-r"
 
 // Check that we don't try to forward -Xclang or -mlinker-version to GCC.
 // PR12920 -- Check also we may not forward W_Group options to GCC.
 //