Mark arm as the 32bit variant of aarch64 in Triple

[tberghammer]

Summary

Mark arm as the 32bit variant of aarch64 in Triple

Change Triple::get32BitArchVariant to return arm/armeb as the 32bit
variant of aarch64/aarch64_be and do the same change for the opposite
direction in Triple::get64BitArchVariant.

Notes:
I hit the issue when investigating a bug in LLDB where we depending on the this behavior. If this is not a reasonable change from LLVM point of view then let me know and I can put a similar change into LLDB instead.
I don't know how can I add a reasonable test for this change into LLVM, but if somebody feels it is necessary for a change like this then please give me some direction.
I verified that check-llvm and check-clang targets aren't reporting any new failure on Linux x86_64 but I don't have an arm/aarch64 device where I can run the tests to verify everything works there as well.

[jmolloy]

LGTM. Does this mean -m32/-m64 will work?! :o

James

[tberghammer]

I am not sure what is the exact functionality of -m32/-m64 but after this change, commands like this are working as expected (for all combination of arm/aarch64):

$ ./bin/clang -target arm-unknown-unknown -m64 -v
clang version 3.8.0 (trunk 256842) (llvm/trunk 256840)
Target: aarch64-unknown-unknown
Thread model: posix
InstalledDir: /mnt/ssd/ll/git/build/host-release/./bin

[rengolin]

In D15529#320525, @tberghammer wrote:

$ ./bin/clang -target arm-unknown-unknown -m64 -v
clang version 3.8.0 (trunk 256842) (llvm/trunk 256840)
Target: aarch64-unknown-unknown

Heh! Whaddya know! :D

Sounds awesome! Once this is in, I'll try -m32 on a multiarch AArch64.

llvm/trunk/lib/Support/Triple.cpp

 bool Triple::isArch16Bit() const {
   return getArchPointerBitWidth(getArch()) == 16;
 }
 
 Triple Triple::get32BitArchVariant() const {
   Triple T(*this);
   switch (getArch()) {
   case Triple::UnknownArch:
-  case Triple::aarch64:
-  case Triple::aarch64_be:
   case Triple::amdgcn:
   case Triple::avr:
   case Triple::bpfel:
   case Triple::bpfeb:
   case Triple::msp430:
   case Triple::systemz:
   case Triple::ppc64le:
     T.setArch(UnknownArch);
Triple Triple::get32BitArchVariant() const {
   case Triple::thumbeb:
   case Triple::x86:
   case Triple::xcore:
   case Triple::shave:
   case Triple::wasm32:
     // Already 32-bit.
     break;
 
-  case Triple::le64:      T.setArch(Triple::le32);    break;
-  case Triple::mips64:    T.setArch(Triple::mips);    break;
-  case Triple::mips64el:  T.setArch(Triple::mipsel);  break;
-  case Triple::nvptx64:   T.setArch(Triple::nvptx);   break;
-  case Triple::ppc64:     T.setArch(Triple::ppc);     break;
-  case Triple::sparcv9:   T.setArch(Triple::sparc);   break;
-  case Triple::x86_64:    T.setArch(Triple::x86);     break;
-  case Triple::amdil64:   T.setArch(Triple::amdil);   break;
-  case Triple::hsail64:   T.setArch(Triple::hsail);   break;
-  case Triple::spir64:    T.setArch(Triple::spir);    break;
-  case Triple::wasm64:    T.setArch(Triple::wasm32);  break;
+  case Triple::aarch64:    T.setArch(Triple::arm);     break;
+  case Triple::aarch64_be: T.setArch(Triple::armeb);   break;
+  case Triple::le64:       T.setArch(Triple::le32);    break;
+  case Triple::mips64:     T.setArch(Triple::mips);    break;
+  case Triple::mips64el:   T.setArch(Triple::mipsel);  break;
+  case Triple::nvptx64:    T.setArch(Triple::nvptx);   break;
+  case Triple::ppc64:      T.setArch(Triple::ppc);     break;
+  case Triple::sparcv9:    T.setArch(Triple::sparc);   break;
+  case Triple::x86_64:     T.setArch(Triple::x86);     break;
+  case Triple::amdil64:    T.setArch(Triple::amdil);   break;
+  case Triple::hsail64:    T.setArch(Triple::hsail);   break;
+  case Triple::spir64:     T.setArch(Triple::spir);    break;
+  case Triple::wasm64:     T.setArch(Triple::wasm32);  break;
   }
   return T;
 }
 
 Triple Triple::get64BitArchVariant() const {
   Triple T(*this);
   switch (getArch()) {
   case Triple::UnknownArch:
-  case Triple::arm:
-  case Triple::armeb:
   case Triple::avr:
   case Triple::hexagon:
   case Triple::kalimba:
   case Triple::msp430:
   case Triple::r600:
   case Triple::tce:
-  case Triple::thumb:
-  case Triple::thumbeb:
   case Triple::xcore:
   case Triple::sparcel:
   case Triple::shave:
     T.setArch(UnknownArch);
     break;
 
   case Triple::aarch64:
   case Triple::aarch64_be:
Triple Triple::get64BitArchVariant() const {
   case Triple::ppc64le:
   case Triple::sparcv9:
   case Triple::systemz:
   case Triple::x86_64:
   case Triple::wasm64:
     // Already 64-bit.
     break;
 
-  case Triple::le32:    T.setArch(Triple::le64);      break;
-  case Triple::mips:    T.setArch(Triple::mips64);    break;
-  case Triple::mipsel:  T.setArch(Triple::mips64el);  break;
-  case Triple::nvptx:   T.setArch(Triple::nvptx64);   break;
-  case Triple::ppc:     T.setArch(Triple::ppc64);     break;
-  case Triple::sparc:   T.setArch(Triple::sparcv9);   break;
-  case Triple::x86:     T.setArch(Triple::x86_64);    break;
-  case Triple::amdil:   T.setArch(Triple::amdil64);   break;
-  case Triple::hsail:   T.setArch(Triple::hsail64);   break;
-  case Triple::spir:    T.setArch(Triple::spir64);    break;
-  case Triple::wasm32:  T.setArch(Triple::wasm64);    break;
+  case Triple::arm:     T.setArch(Triple::aarch64);    break;
+  case Triple::armeb:   T.setArch(Triple::aarch64_be); break;
+  case Triple::le32:    T.setArch(Triple::le64);       break;
+  case Triple::mips:    T.setArch(Triple::mips64);     break;
+  case Triple::mipsel:  T.setArch(Triple::mips64el);   break;
+  case Triple::nvptx:   T.setArch(Triple::nvptx64);    break;
+  case Triple::ppc:     T.setArch(Triple::ppc64);      break;
+  case Triple::sparc:   T.setArch(Triple::sparcv9);    break;
+  case Triple::x86:     T.setArch(Triple::x86_64);     break;
+  case Triple::amdil:   T.setArch(Triple::amdil64);    break;
+  case Triple::hsail:   T.setArch(Triple::hsail64);    break;
+  case Triple::spir:    T.setArch(Triple::spir64);     break;
+  case Triple::thumb:   T.setArch(Triple::aarch64);    break;
+  case Triple::thumbeb: T.setArch(Triple::aarch64_be); break;
+  case Triple::wasm32:  T.setArch(Triple::wasm64);     break;
   }
   return T;
 }
 
 Triple Triple::getBigEndianArchVariant() const {
   Triple T(*this);
   switch (getArch()) {
   case Triple::UnknownArch: