[mips] Notify user that `-mabicalls` is ignored on non-PIC N64 ABI

[atanasyan]

Summary

The -mabicalls option does not make sense in the case of non position independent code for the N64 ABI. After this change the driver shows a warning that -mabicalls is ignored in that case.

[sdardis]

Slight tweak to the summary:

The -mabicalls option does not have a sense in case of non position independent code on N64 ABI. After this change driver starts to show a warning that -mabicalls is ignored in that case.

The -mabicalls option does not make sense in the case of non position independent code for the N64 ABI. After this change the driver shows a warning that -mabicalls is ignored in that case.

I think the major change in this patch is overly complex for what it should be, suggestion inline.

include/clang/Basic/DiagnosticDriverKinds.td

297

and the N64 ABI

lib/Driver/ToolChains/Arch/Mips.cpp

233–253

I think this logic can be simplified to:

bool UseAbiCalls = false;                                                                                            

Arg *ABICallsArg =
    Args.getLastArg(options::OPT_mabicalls, options::OPT_mno_abicalls);                                              
UseAbiCalls =
    !ABICallsArg || 
    (ABICallsArg && ABICallsArg->getOption().matches(options::OPT_mabicalls));                                       

if (UseAbiCalls && IsN64 && NonPIC) {
  D.Diag(diag::warn_drv_unsupported_abicalls);                                                                       
  UseAbiCalls = false;                                                                                               
}                                                                                                                    

if (!UseAbiCalls)
  Features.push_back("+noabicalls");                                                                                 
else
  Features.push_back("-noabicalls");

As that way we immediately pick up the implicit case or explicit case of using -mabicalls and we can simply pick out the N64 && NonPic && UseAbiCalls case to warn and fix.

Although we don't need to add "-noabicalls" to the Features vector, the backend defaults to that, though the tests expect it.

[atanasyan]

• Addressed review comments.

[sdardis]

Nit: my comment on line 297, "non position-independent code and N64 ABI" should be "non position-independent code and the N64 ABI".

LGTM otherwise.

include/clang/Basic/DiagnosticDriverKinds.td

def warn_target_unsupported_nanlegacy : Warning<
   InGroup<UnsupportedNan>;
 def warn_target_unsupported_compact_branches : Warning<
   "ignoring '-mcompact-branches=' option because the '%0' architecture does not"
   " support it">, InGroup<UnsupportedCB>;
 def warn_drv_unsupported_gpopt : Warning<
   "ignoring '-mgpopt' option as it cannot be used with %select{|the implicit"
   " usage of }0-mabicalls">,
   InGroup<UnsupportedGPOpt>;
+def warn_drv_unsupported_abicalls : Warning<
+  "ignoring '-mabicalls' option as it cannot be used with "
+  "non position-independent code and the N64 ABI">,
+  InGroup<OptionIgnored>;
 
 def warn_drv_unable_to_find_directory_expected : Warning<
   "unable to find %0 directory, expected to be in '%1'">,
   InGroup<InvalidOrNonExistentDirectory>, DefaultIgnore;
 
 def warn_drv_ps4_force_pic : Warning<
   "option '%0' was ignored by the PS4 toolchain, using '-fPIC'">,
   InGroup<OptionIgnored>;

lib/Driver/ToolChains/Arch/Mips.cpp

Arg *LastPICArg = Args.getLastArg(options::OPT_fPIC, options::OPT_fno_PIC,
                                     options::OPT_fpie, options::OPT_fno_pie);
   if (LastPICArg) {
     Option O = LastPICArg->getOption();
     NonPIC =
         (O.matches(options::OPT_fno_PIC) || O.matches(options::OPT_fno_pic) ||
          O.matches(options::OPT_fno_PIE) || O.matches(options::OPT_fno_pie));
   }
 
-  if (IsN64 && NonPIC)
+  bool UseAbiCalls = false;
+
+  Arg *ABICallsArg =
+      Args.getLastArg(options::OPT_mabicalls, options::OPT_mno_abicalls);
+  UseAbiCalls =
+      !ABICallsArg ||
+      (ABICallsArg && ABICallsArg->getOption().matches(options::OPT_mabicalls));
+
+  if (UseAbiCalls && IsN64 && NonPIC) {
+    D.Diag(diag::warn_drv_unsupported_abicalls);
+    UseAbiCalls = false;
+  }
+
+  if (!UseAbiCalls)
     Features.push_back("+noabicalls");
   else
-    AddTargetFeature(Args, Features, options::OPT_mno_abicalls,
-                     options::OPT_mabicalls, "noabicalls");
+    Features.push_back("-noabicalls");
 
   mips::FloatABI FloatABI = mips::getMipsFloatABI(D, Args);
   if (FloatABI == mips::FloatABI::Soft) {
     // FIXME: Note, this is a hack. We need to pass the selected float
     // mode to the MipsTargetInfoBase to define appropriate macros there.
     // Now it is the only method.
     Features.push_back("+soft-float");
   }
 
   if (Arg *A = Args.getLastArg(options::OPT_mnan_EQ)) {
     StringRef Val = StringRef(A->getValue());
     if (Val == "2008") {
       if (mips::getSupportedNanEncoding(CPUName) & mips::Nan2008)
         Features.push_back("+nan2008");
       else {

test/Driver/mips-abicalls-warning.c

+// REQUIRES: mips-registered-target
+// RUN: %clang -### -c -target mips64-mti-elf -fno-PIC -mabicalls %s 2>&1 | FileCheck %s
+// CHECK: warning: ignoring '-mabicalls' option as it cannot be used with non position-independent code and the N64 ABI

test/Driver/mips-features.c

 // Check handling MIPS specific features options.
 //
 // -mabicalls
 // RUN: %clang -target mips-linux-gnu -### -c %s -mno-abicalls -mabicalls 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MABICALLS %s
 // CHECK-MABICALLS: "-target-feature" "-noabicalls"
 //
 // -mno-abicalls
 // RUN: %clang -target mips-linux-gnu -### -c %s -mabicalls -mno-abicalls 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MNOABICALLS %s
 // CHECK-MNOABICALLS: "-target-feature" "+noabicalls"
 //
+// -mno-abicalls non-PIC N64
+// RUN: %clang -target mips64-linux-gnu -### -c -fno-PIC %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MNOABICALLS-N64NPIC %s
+// CHECK-MNOABICALLS-N64NPIC: "-target-feature" "+noabicalls"
+//
 // -mgpopt
 // RUN: %clang -target mips-linux-gnu -### -c %s -mno-gpopt -mgpopt -Wno-unsupported-gpopt 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MGPOPT-DEF-ABICALLS %s
 // CHECK-MGPOPT-DEF-ABICALLS-NOT: "-mllvm" "-mgpopt"
 //
 // -mabicalls -mgpopt
 // RUN: %clang -target mips-linux-gnu -### -c %s -mabicalls -mno-gpopt -mgpopt -Wno-unsupported-gpopt 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MGPOPT-EXPLICIT-ABICALLS %s