[AIX] Emit error for -G option on AIX

[Xiangling_L]

Summary

1. Emit error for -G driver option on AIX
2. Adjust cmake file to use -Wl,-G instead of -G

Rationale to error on -G:
On AIX, legacy XL compiler uses -G to produce a shared object enabled for use with the run-time linker, which has different meanings from what it is used for in Clang. And in Clang, other targets do not have -G map to another functionality in their legacy compiler. So this error is more important when we are on AIX.

[jasonliu]

Could we add some rationale to the patch summary about why we would want to deliberately emitting an error for AIX?

clang/lib/Driver/ToolChains/Clang.cpp

4961

Question: When do we query RawTriple, and when we should query Triple?

[Xiangling_L]

clang/lib/Driver/ToolChains/Clang.cpp

4961

RawTriple in this function means the triple you passed in or the default one.

Triple in this function means a ToolChain's effective triple.
An effective triple is:

the Clang triple to use for this target, which may take into account the command line arguments. For example, on Darwin the -mmacosx-version-min= command line argument (which
sets the deployment target) determines the version in the triple passed to Clang.

So I feel, if there is no special condition we need to consider, we just use RawTriple.

[hubert.reinterpretcast]

clang/test/Driver/aix-err-options.c

2

Does this need a call to not?

[hubert.reinterpretcast]

clang/lib/Driver/ToolChains/Clang.cpp

4962

Either remove the braces here or add braces for the outer block.

Refer to the

// Use braces for the outer `if` since the nested `for` is braced.

example under https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements.

[Xiangling_L]

clang/test/Driver/aix-err-options.c

2

Using not will fail the testcase.

[Xiangling_L]

Fix the formatting issues;

[hubert.reinterpretcast]

LGTM; thanks!

clang/test/Driver/aix-err-options.c

2

Got it; didn't know -### has such an effect on the return code.

clang/lib/Driver/ToolChains/Clang.cpp

CmdArgs.push_back(D.CCLogDiagnosticsFilename ? D.CCLogDiagnosticsFilename
                                                  : "-");
   }
 
   // Give the gen diagnostics more chances to succeed, by avoiding intentional
   // crashes.
   if (D.CCGenDiagnostics)
     CmdArgs.push_back("-disable-pragma-debug-crash");
 
+  if (RawTriple.isOSAIX())
+    if (Arg *A = Args.getLastArg(options::OPT_G))
+      D.Diag(diag::err_drv_unsupported_opt_for_target)
+          << A->getSpelling() << RawTriple.str();
+
   bool UseSeparateSections = isUseSeparateSections(Triple);
 
   if (Args.hasFlag(options::OPT_ffunction_sections,
                    options::OPT_fno_function_sections, UseSeparateSections)) {
     CmdArgs.push_back("-ffunction-sections");
   }
 
   if (Arg *A = Args.getLastArg(options::OPT_fbasic_block_sections_EQ)) {

clang/test/Driver/aix-err-options.c

+// RUN: %clang -target powerpc32-ibm-aix-xcoff -### -S -emit-llvm -G 0 2>&1 %s | \
+// RUN:   FileCheck --check-prefix=CHECK32 %s
+// RUN: %clang -target powerpc64-ibm-aix-xcoff -### -S -emit-llvm -G 0 2>&1 %s | \
+// RUN:   FileCheck --check-prefix=CHECK64 %s
+
+// CHECK32: error: unsupported option '-G' for target 'powerpc32-ibm-aix-xcoff'
+// CHECK64: error: unsupported option '-G' for target 'powerpc64-ibm-aix-xcoff'

llvm/CMakeLists.txt

if(CMAKE_VERSION VERSION_LESS 3.16)
     string(REGEX REPLACE "(^|[ \t]+)(-Wl,)?-G([ \t]+|$)" "" CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS
       "${CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS}")
     string(REGEX REPLACE "(^|[ \t]+)(-Wl,)?-G([ \t]+|$)" "" CMAKE_SHARED_LIBRARY_CREATE_ASM_FLAGS
       "${CMAKE_SHARED_LIBRARY_CREATE_ASM_FLAGS}")
   endif()
 
   # Modules should be built with -G, so we can use runtime linking with
   # plugins.
-  string(APPEND CMAKE_MODULE_LINKER_FLAGS " -G")
+  string(APPEND CMAKE_MODULE_LINKER_FLAGS " -Wl,-G")
 
   # Also set the correct flags for building shared libraries.
   string(APPEND CMAKE_SHARED_LINKER_FLAGS " -shared")
 endif()
 
 # Build with _XOPEN_SOURCE on z/OS.
 if (CMAKE_SYSTEM_NAME MATCHES "OS390")
   add_definitions("-D_XOPEN_SOURCE=600")