[compiler-rt] Fix invalid triple on ARM build

[luporl]

Summary

The fuzzer build was failing on armv7l, with an invalid triple
error. This happened because CMake's get_compiler_rt_target
function was missing some code to correctly handle arm archs,
such as armhf.

The cmake command that caused the build failure was:

cmake --fresh -S "$PWD/llvm/" -B "$PWD/build/" -G Ninja \
  -DCMAKE_INSTALL_PREFIX="$PWD/install" \
  -DCMAKE_BUILD_TYPE=Release \
  -DLLVM_ENABLE_PROJECTS="clang;lld;lldb;clang-tools-extra;polly" \
  -DLLVM_ENABLE_RUNTIMES="compiler-rt;libcxx;libcxxabi;libunwind" \
  -DLLVM_TOOLCHAIN_TOOLS="llvm-ar;llvm-ranlib;llvm-objdump;\
llvm-rc;llvm-cvtres;llvm-nm;llvm-strings;llvm-readobj;\
llvm-dlltool;llvm-pdbutil;llvm-objcopy;llvm-strip;llvm-cov;\
llvm-profdata;llvm-addr2line;llvm-symbolizer;llvm-windres;llvm-ml;\
llvm-readelf;llvm-size" \
  -DLLVM_INSTALL_BINUTILS_SYMLINKS=OFF -DLLVM_PARALLEL_LINK_JOBS=1

The fix was extracted from D140011.

[phosek]

Can we land D140011 instead?

[DavidSpickett]

Can we land D140011 instead?

Will do.

[DavidSpickett]

Done. This is not needed on main now, we'll cherry pick this portion to 16 as needed.

[luporl]

Abandoned in favor of D140011.

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

elseif("${arch}" MATCHES "mips64|mips64el")
     string(REGEX REPLACE "^mips$" "mips64" triple_cpu_mips "${triple_cpu_mips}")
     string(REGEX REPLACE "^mipsel$" "mips64el" triple_cpu_mips "${triple_cpu_mips}")
     set(target "${triple_cpu_mips}${triple_suffix_gnu}")
   elseif("${arch}" MATCHES "mips|mipsel")
     string(REGEX REPLACE "-gnuabi.*" "-gnu" triple_suffix_gnu "${triple_suffix}")
     string(REGEX REPLACE "mipsisa64" "mipsisa32" triple_cpu_mips "${triple_cpu}")
     string(REGEX REPLACE "mips64" "mips" triple_cpu_mips "${triple_cpu_mips}")
     set(target "${triple_cpu_mips}${triple_suffix_gnu}")
+  elseif("${arch}" MATCHES "^arm")
+    # Arch is arm, armhf, armv6m (anything else would come from using
+    # COMPILER_RT_DEFAULT_TARGET_ONLY, which is checked above).
+    if (${arch} STREQUAL "armhf")
+      # If we are building for hard float but our ABI is soft float.
+      if ("${triple_suffix}" MATCHES ".*eabi$")
+        # Change "eabi" -> "eabihf"
+        set(triple_suffix "${triple_suffix}hf")
+      endif()
+      # ABI is already set in the triple, don't repeat it in the architecture.
+      set(arch "arm")
+    else ()
+      # If we are building for soft float, but the triple's ABI is hard float.
+      if ("${triple_suffix}" MATCHES ".*eabihf$")
+        # Change "eabihf" -> "eabi"
+        string(REGEX REPLACE "hf$" "" triple_suffix "${triple_suffix}")
+      endif()
+    endif()
+    set(target "${arch}${triple_suffix}")
   else()
     set(target "${arch}${triple_suffix}")
   endif()
   set(${variable} ${target} PARENT_SCOPE)
 endfunction()
 
 function(get_compiler_rt_install_dir arch install_dir)
   if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)