[clang][AVR] add more builtin macros

[MaskRay]

avr-gcc -E -dM -xc /dev/null -dM | grep __avr has no result, so I am not sure this is correct.

[benshi001]

In D123567#3444579, @MaskRay wrote:

avr-gcc -E -dM -xc /dev/null -dM | grep __avr has no result, so I am not sure this is correct.

The reason I added these little case macros, is that I find other backend targets have, as shown in the compiler-rt's CMakefile, https://github.com/llvm/llvm-project/blob/main/compiler-rt/cmake/Modules/CompilerRTUtils.cmake#L155

I think we need not strictly follow avr-gcc's way, my final goal is making clang+llvm+compiler-rt+lld fully functional and can replace avr-gcc toolchain.

I expect clang+llvm+compiler-rt+lld to be fully functioning against the Arduino boards. (https://www.arduino.cc/).

[MaskRay]

In D123567#3444613, @benshi001 wrote:

In D123567#3444579, @MaskRay wrote:

avr-gcc -E -dM -xc /dev/null -dM | grep __avr has no result, so I am not sure this is correct.

The reason I added these little case macros, is that I find other backend targets have, as shown in the compiler-rt's CMakefile, https://github.com/llvm/llvm-project/blob/main/compiler-rt/cmake/Modules/CompilerRTUtils.cmake#L155

I think we need not strictly follow avr-gcc's way, my final goal is making clang+llvm+compiler-rt+lld fully functional and can replace avr-gcc toolchain.

I expect clang+llvm+compiler-rt+lld to be fully functioning against the Arduino boards. (https://www.arduino.cc/).

Err, this is not sufficient justification to introduce new preprocessor macros. Changing the predefined macro set to make an in-tree cmake function happy. I am unsure this is the right thing.
If the cmake function isn't happy with a lowercase macro, can't you fix it?

[benshi001]

In D123567#3444674, @MaskRay wrote:

In D123567#3444613, @benshi001 wrote:

In D123567#3444579, @MaskRay wrote:

avr-gcc -E -dM -xc /dev/null -dM | grep __avr has no result, so I am not sure this is correct.

The reason I added these little case macros, is that I find other backend targets have, as shown in the compiler-rt's CMakefile, https://github.com/llvm/llvm-project/blob/main/compiler-rt/cmake/Modules/CompilerRTUtils.cmake#L155

I think we need not strictly follow avr-gcc's way, my final goal is making clang+llvm+compiler-rt+lld fully functional and can replace avr-gcc toolchain.

I expect clang+llvm+compiler-rt+lld to be fully functioning against the Arduino boards. (https://www.arduino.cc/).

Err, this is not sufficient justification to introduce new preprocessor macros. Changing the predefined macro set to make an in-tree cmake function happy. I am unsure this is the right thing.
If the cmake function isn't happy with a lowercase macro, can't you fix it?

I am not sure if there are other concerns of using lower case macros in compiler-rt's CMake, and I will check that.

clang/lib/Basic/Targets/AVR.cpp

bool AVRTargetInfo::setCPU(const std::string &Name) {
   // Parameter Name is neither valid family name nor valid device name.
   return false;
 }
 
 void AVRTargetInfo::getTargetDefines(const LangOptions &Opts,
                                      MacroBuilder &Builder) const {
   Builder.defineMacro("AVR");
   Builder.defineMacro("__AVR");
+  Builder.defineMacro("__avr");
   Builder.defineMacro("__AVR__");
+  Builder.defineMacro("__avr__");
   Builder.defineMacro("__ELF__");
 
   if (!this->CPU.empty()) {
     auto It = llvm::find_if(
         AVRMcus, [&](const MCUInfo &Info) { return Info.Name == this->CPU; });
 
     if (It != std::end(AVRMcus)) {
       Builder.defineMacro(It->DefineName);

clang/test/Preprocessor/avr-common.c

 // RUN: %clang_cc1 -E -dM -triple avr-unknown-unknown /dev/null | FileCheck -match-full-lines %s
 
 // CHECK: #define AVR 1
 // CHECK: #define __AVR 1
 // CHECK: #define __AVR__ 1
 // CHECK: #define __ELF__ 1
+// CHECK: #define __avr 1
+// CHECK: #define __avr__ 1