[compiler-rt][AIX] Add CMake support for 32-bit Power builds

[daltenty]

Summary

This patch enables support for building compiler-rt builtins for 32-bit
Power arch on AIX. For now, we leave out the specialized ppc builtin
implementations for 128-bit long double and friends since those will
need some special handling for AIX.

[hubert.reinterpretcast]

LGTM; thanks.

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

 
 macro(detect_target_arch)
   check_symbol_exists(__arm__ "" __ARM)
   check_symbol_exists(__aarch64__ "" __AARCH64)
   check_symbol_exists(__x86_64__ "" __X86_64)
   check_symbol_exists(__i386__ "" __I386)
   check_symbol_exists(__mips__ "" __MIPS)
   check_symbol_exists(__mips64__ "" __MIPS64)
+  check_symbol_exists(__powerpc__ "" __PPC)
   check_symbol_exists(__powerpc64__ "" __PPC64)
   check_symbol_exists(__powerpc64le__ "" __PPC64LE)
   check_symbol_exists(__riscv "" __RISCV)
   check_symbol_exists(__s390x__ "" __S390X)
   check_symbol_exists(__sparc "" __SPARC)
   check_symbol_exists(__sparcv9 "" __SPARCV9)
   check_symbol_exists(__wasm32__ "" __WEBASSEMBLY32)
   check_symbol_exists(__wasm64__ "" __WEBASSEMBLY64)
   check_symbol_exists(__ve__ "" __VE)
   if(__ARM)
     add_default_target_arch(arm)
   elseif(__AARCH64)
     add_default_target_arch(aarch64)
   elseif(__X86_64)
     add_default_target_arch(x86_64)
   elseif(__I386)
     add_default_target_arch(i386)
   elseif(__MIPS64) # must be checked before __MIPS
     add_default_target_arch(mips64)
   elseif(__MIPS)
     add_default_target_arch(mips)
-  elseif(__PPC64)
+  elseif(__PPC64) # must be checked before __PPC
     add_default_target_arch(powerpc64)
   elseif(__PPC64LE)
     add_default_target_arch(powerpc64le)
+  elseif(__PPC)
+    add_default_target_arch(powerpc)
   elseif(__RISCV)
     if(CMAKE_SIZEOF_VOID_P EQUAL "4")
       add_default_target_arch(riscv32)
     elseif(CMAKE_SIZEOF_VOID_P EQUAL "8")
       add_default_target_arch(riscv64)
     else()
       message(FATAL_ERROR "Unsupport XLEN for RISC-V")
     endif()

compiler-rt/cmake/base-config-ix.cmake

elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "powerpc")
       # Strip out -nodefaultlibs when calling TEST_BIG_ENDIAN. Configuration
       # will fail with this option when building with a sanitizer.
       cmake_push_check_state()
       string(REPLACE "-nodefaultlibs" "" CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")
       TEST_BIG_ENDIAN(HOST_IS_BIG_ENDIAN)
       cmake_pop_check_state()
 
       if(HOST_IS_BIG_ENDIAN)
+        if(CMAKE_SYSTEM_NAME MATCHES "AIX")
+          test_target_arch(powerpc "" "-m32")
+        endif()
           test_target_arch(powerpc64 "" "-m64")
       else()
         test_target_arch(powerpc64le "" "-m64")
       endif()
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "s390x")
       test_target_arch(s390x "" "")
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "sparc")
       test_target_arch(sparc "" "-m32")
       test_target_arch(sparcv9 "" "-m64")

compiler-rt/cmake/builtin-config-ix.cmake

 
 set(ARM64 aarch64)
 set(ARM32 arm armhf armv6m armv7m armv7em armv7 armv7s armv7k)
 set(HEXAGON hexagon)
 set(X86 i386)
 set(X86_64 x86_64)
 set(MIPS32 mips mipsel)
 set(MIPS64 mips64 mips64el)
+set(PPC32 powerpc)
 set(PPC64 powerpc64 powerpc64le)
 set(RISCV32 riscv32)
 set(RISCV64 riscv64)
 set(SPARC sparc)
 set(SPARCV9 sparcv9)
 set(WASM32 wasm32)
 set(WASM64 wasm64)
 set(VE ve)
 
 if(APPLE)
   set(ARM64 arm64 arm64e)
   set(ARM32 armv7 armv7k armv7s)
   set(X86_64 x86_64 x86_64h)
 endif()
 
 set(ALL_BUILTIN_SUPPORTED_ARCH
   ${X86} ${X86_64} ${ARM32} ${ARM64}
-  ${HEXAGON} ${MIPS32} ${MIPS64} ${PPC64}
+  ${HEXAGON} ${MIPS32} ${MIPS64} ${PPC32} ${PPC64}
   ${RISCV32} ${RISCV64} ${SPARC} ${SPARCV9}
   ${WASM32} ${WASM64} ${VE})
 
 include(CompilerRTUtils)
 include(CompilerRTDarwinUtils)
 
 if(APPLE)
 

compiler-rt/lib/builtins/CMakeLists.txt

 
 set(mips_SOURCES ${GENERIC_SOURCES})
 set(mipsel_SOURCES ${mips_SOURCES})
 set(mips64_SOURCES ${GENERIC_TF_SOURCES}
                    ${mips_SOURCES})
 set(mips64el_SOURCES ${GENERIC_TF_SOURCES}
                      ${mips_SOURCES})
 
+set(powerpc_SOURCES ${GENERIC_SOURCES})
+
 set(powerpc64_SOURCES
   ppc/divtc3.c
   ppc/fixtfdi.c
   ppc/fixunstfdi.c
   ppc/floatditf.c
   ppc/floatunditf.c
   ppc/gcc_qadd.c
   ppc/gcc_qdiv.c