[Clang][Driver] Recognize the AIX OBJECT_MODE environment setting

[daltenty]

Summary

AIX uses an environment variable called OBJECT_MODE to indicate to
utilities in the toolchain whether they should be operating in 32-bit or
64-bit mode. This patch makes the clang driver recognize the current
OBJECT_MODE setting when we are operating with an AIX target and adds a
custom diagnostic for invalid settings.

For more details about OBJECT_MODE on AIX see:

https://www.ibm.com/support/knowledgecenter/SSGH2K_13.1.3/com.ibm.xlc1313.aix.doc/compiler_ref/tusetenv1.html
https://www.ibm.com/support/knowledgecenter/SSGH2K_13.1.3/com.ibm.xlc1313.aix.doc/compiler_ref/opt_3264.html

[jasonliu]

LGTM.

[hubert.reinterpretcast]

LGTM with minor nit.

clang/lib/Driver/Driver.cpp

479

Just a note: I guess having an AIX target is an okay proxy for being on AIX here... I don't think enabling OBJECT_MODE for other targets when building on AIX is superior.

clang/test/Driver/aix-object-mode.c

2

Minor nit: Add "that" between "Check" and "setting".

clang/include/clang/Basic/DiagnosticDriverKinds.td

def warn_drv_msp430_hwmult_no_device : Warning<"no MCU device specified, but "
   "explicitly.">, InGroup<InvalidCommandLineArgument>;
 
 def warn_drv_libstdcxx_not_found : Warning<
   "include path for libstdc++ headers not found; pass '-stdlib=libc++' on the "
   "command line to use the libc++ standard library instead">,
   InGroup<DiagGroup<"stdlibcxx-not-found">>;
 
 def err_drv_cannot_mix_options : Error<"cannot specify '%1' along with '%0'">;
+
+def err_drv_invalid_object_mode : Error<"OBJECT_MODE setting %0 is not recognized and is not a valid setting.">;
 }

clang/lib/Driver/Driver.cpp

if (Arg *A = Args.getLastArg(options::OPT_mlittle_endian,
     }
   }
 
   // Skip further flag support on OSes which don't support '-m32' or '-m64'.
   if (Target.getArch() == llvm::Triple::tce ||
       Target.getOS() == llvm::Triple::Minix)
     return Target;
 
+  // On AIX, the env OBJECT_MODE may affect the resulting arch variant.
+  if (Target.isOSAIX()) {
+    if (Optional<std::string> ObjectModeValue =
+            llvm::sys::Process::GetEnv("OBJECT_MODE")) {
+      StringRef ObjectMode = *ObjectModeValue;
+      llvm::Triple::ArchType AT = llvm::Triple::UnknownArch;
+
+      if (ObjectMode.equals("64")) {
+        AT = Target.get64BitArchVariant().getArch();
+      } else if (ObjectMode.equals("32")) {
+        AT = Target.get32BitArchVariant().getArch();
+      } else {
+        D.Diag(diag::err_drv_invalid_object_mode) << ObjectMode;
+      }
+
+      if (AT != llvm::Triple::UnknownArch && AT != Target.getArch())
+        Target.setArch(AT);
+    }
+  }
+
   // Handle pseudo-target flags '-m64', '-mx32', '-m32' and '-m16'.
   Arg *A = Args.getLastArg(options::OPT_m64, options::OPT_mx32,
                            options::OPT_m32, options::OPT_m16);
   if (A) {
     llvm::Triple::ArchType AT = llvm::Triple::UnknownArch;
 
     if (A->getOption().matches(options::OPT_m64)) {
       AT = Target.get64BitArchVariant().getArch();

clang/test/Driver/aix-object-mode.c

+// Check that setting an OBJECT_MODE converts the AIX triple to the right variant.
+// RUN: env OBJECT_MODE=64 \
+// RUN: %clang -target powerpc-ibm-aix -print-target-triple | FileCheck -check-prefix=CHECK64 %s
+
+// RUN: env OBJECT_MODE=32 \
+// RUN: %clang -target powerpc64-ibm-aix -print-target-triple | FileCheck -check-prefix=CHECK32 %s
+
+// Command-line options win.
+// RUN: env OBJECT_MODE=64 \
+// RUN: %clang -target powerpc64-ibm-aix -print-target-triple -m32 | FileCheck -check-prefix=CHECK32 %s
+
+// RUN: env OBJECT_MODE=32 \
+// RUN: %clang -target powerpc-ibm-aix -print-target-triple -m64 | FileCheck -check-prefix=CHECK64 %s
+
+// CHECK32: powerpc-ibm-aix
+// CHECK64: powerpc64-ibm-aix
+
+// Emit a diagnostic if there is an invalid mode.
+// RUN: env OBJECT_MODE=31 \
+// RUN: not %clang -target powerpc-ibm-aix 2>&1 | FileCheck -check-prefix=DIAG %s
+
+// DIAG: error: OBJECT_MODE setting 31 is not recognized and is not a valid setting.