[mips] Teach the driver to accept -m(no-)gpopt.

[sdardis]

Summary

This patch teaches the driver to pass -mgpopt by default to the backend when it
is supported, i.e. we are using -mno-abicalls.

[atanasyan]

lib/Driver/ToolChains/Clang.cpp

1490

Could it be rewritten a bit shorter?

bool NoAbiCalls =
    ABICalls && ABICalls->getOption().matches(options::OPT_mno_abicalls);
bool WantGPOpt = GPOpt && GPOpt->getOption().matches(options::OPT_mgpopt);

if (NoAbiCalls && (!GPOpt || WantGPOpt)) {
  CmdArgs.push_back("-mllvm");
  CmdArgs.push_back("-mgpopt=1");
} else {
  CmdArgs.push_back("-mllvm");
  CmdArgs.push_back("-mgpopt=0");
}

if (GPOpt)
  GPOpt->claim();

[sdardis]

lib/Driver/ToolChains/Clang.cpp

1490

Yes, it can. I think I mis-handled the case where -mabicalls and -mgpopt are combined. I'll reflow the logic along the lines of your suggestion and add a warning.

[sdardis]

Addressed review comment, added warning when combining -mabicalls and -mgpopt.

[atanasyan]

LGTM

include/clang/Driver/Options.td

 def mmt : Flag<["-"], "mmt">, Group<m_Group>,
   HelpText<"Enable MT ASE (MIPS only)">;
 def mno_mt : Flag<["-"], "mno-mt">, Group<m_Group>,
   HelpText<"Disable MT ASE (MIPS only)">;
 def mfp64 : Flag<["-"], "mfp64">, Group<m_Group>,
   HelpText<"Use 64-bit floating point registers (MIPS only)">;
 def mfp32 : Flag<["-"], "mfp32">, Group<m_Group>,
   HelpText<"Use 32-bit floating point registers (MIPS only)">;
+def mgpopt : Flag<["-"], "mgpopt">, Group<m_Group>,
+  HelpText<"Use GP relative accesses for symbols known to be in a small"
+           " data section (MIPS)">;
+def mno_gpopt : Flag<["-"], "mno-gpopt">, Group<m_Group>,
+  HelpText<"Do not use GP relative accesses for symbols known to be in a small"
+           " data section (MIPS)">;
 def mnan_EQ : Joined<["-"], "mnan=">, Group<m_Group>;
 def mabicalls : Flag<["-"], "mabicalls">, Group<m_Group>,
   HelpText<"Enable SVR4-style position-independent code (Mips only)">;
 def mno_abicalls : Flag<["-"], "mno-abicalls">, Group<m_Group>,
   HelpText<"Disable SVR4-style position-independent code (Mips only)">;
 def mips1 : Flag<["-"], "mips1">,
   Alias<march_EQ>, AliasArgs<["mips1"]>,
   HelpText<"Equivalent to -march=mips1">, Flags<[HelpHidden]>;

lib/Driver/ToolChains/Clang.cpp

void Clang::AddMIPSTargetArgs(const ArgList &Args,
 
   if (Arg *A = Args.getLastArg(options::OPT_G)) {
     StringRef v = A->getValue();
     CmdArgs.push_back("-mllvm");
     CmdArgs.push_back(Args.MakeArgString("-mips-ssection-threshold=" + v));
     A->claim();
   }
 
+  Arg *GPOpt = Args.getLastArg(options::OPT_mgpopt, options::OPT_mno_gpopt);
+  Arg *ABICalls = Args.getLastArg(options::OPT_mabicalls, options::OPT_mno_abicalls);
+
+  // -mabicalls is the default for many MIPS environments, even with -fno-pic.
+  // -mgpopt is the default for static, -fno-pic environments but these two
+  // options conflict. We want to be certain that -mno-abicalls -mgpopt is
+  // the only case where -mllvm -mgpopt is passed.
+  // NOTE: We need a warning here or in the backend to warn when -mgpopt is
+  //       passed explicitly when compiling something with -mabicalls
+  //       (implictly) in affect. Currently the warning is in the backend.
+  bool WantABICalls =
+      ABICalls && ABICalls->getOption().matches(options::OPT_mabicalls);
+  bool WantGPOpt = GPOpt && GPOpt->getOption().matches(options::OPT_mgpopt);
+  bool DefaultABICalls = !ABICalls;
+  if (!DefaultABICalls && !WantABICalls) {
+    if (!GPOpt || WantGPOpt) {
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back("-mgpopt=1");
+    } else {
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back("-mgpopt=0");
+    }
+
+    if (GPOpt)
+      GPOpt->claim();
+  }
+
   if (Arg *A = Args.getLastArg(options::OPT_mcompact_branches_EQ)) {
     StringRef Val = StringRef(A->getValue());
     if (mips::hasCompactBranches(CPUName)) {
       if (Val == "never" || Val == "always" || Val == "optimal") {
         CmdArgs.push_back("-mllvm");
         CmdArgs.push_back(Args.MakeArgString("-mips-compact-branches=" + Val));
       } else
         D.Diag(diag::err_drv_unsupported_option_argument)

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"
 //
+// -mgpopt
+// RUN: %clang -target mips-linux-gnu -### -c %s -mno-gpopt -mgpopt 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 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MGPOPT-EXPLICIT-ABICALLS %s
+// CHECK-MGPOPT-EXPLICIT-ABICALLS-NOT: "-mllvm" "-mgpopt"
+//
+// -mno-abicalls -mgpopt
+// RUN: %clang -target mips-linux-gnu -### -c %s -mno-abicalls -mno-gpopt -mgpopt 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MGPOPT %s
+// CHECK-MGPOPT: "-mllvm" "-mgpopt=1"
+//
+// -mno-abicalls -mno-gpopt
+// RUN: %clang -target mips-linux-gnu -### -c %s -mno-abicalls -mgpopt -mno-gpopt 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MNOGPOPT %s
+// CHECK-MNOGPOPT: "-mllvm" "-mgpopt=0"
+//
+// -mno-abicalls
+// RUN: %clang -target mips-linux-gnu -### -c %s -mno-abicalls 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MGPOPTDEF %s
+// CHECK-MGPOPTDEF: "-mllvm" "-mgpopt=1"
+//
 // -mips16
 // RUN: %clang -target mips-linux-gnu -### -c %s \
 // RUN:     -mno-mips16 -mips16 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MIPS16 %s
 // CHECK-MIPS16: "-target-feature" "+mips16"
 //
 // -mno-mips16
 // RUN: %clang -target mips-linux-gnu -### -c %s \