Extend small data threshold driver options to PPC target

[jackoalan]

Summary

Clang-side extension of D26344

Exposes PPC target to various small data threshold arguments. Also extends alternate forms to other MIPS uses.

[jackoalan]

Rebase against latest master.

[jackoalan]

Rebase against upstream master

[rsmith]

As of r293254, the -G= and -msmall-data-threshold= flags are just aliases of -G, so you don't need those parts of this patch any more. The PPC part looks fine, but please add a testcase.

In future, please add cfe-commits as a subscriber to Clang changes; otherwise mail doesn't get sent there and patches tend to get lost.

[jackoalan]

Remove already-aliased option matchings; add test case for patch.

[rsmith]

LGTM

lib/Driver/Tools.cpp

if (FloatABI == ppc::FloatABI::Soft) {
     CmdArgs.push_back("-mfloat-abi");
     CmdArgs.push_back("hard");
   }
 
   if (ABIName) {
     CmdArgs.push_back("-target-abi");
     CmdArgs.push_back(ABIName);
   }
+
+  if (Arg *A = Args.getLastArg(options::OPT_G)) {
+    StringRef v = A->getValue();
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back(Args.MakeArgString("-ppc-ssection-threshold=" + v));
+    A->claim();
+  }
 }
 
 bool ppc::hasPPCAbiArg(const ArgList &Args, const char *Value) {
   Arg *A = Args.getLastArg(options::OPT_mabi_EQ);
   return A && (A->getValue() == StringRef(Value));
 }
 
 /// Get the (LLVM) name of the R600 gpu we are targeting.

test/Driver/ppc-eabi-small-data.c

+// Check passing PowerPC EABI small-data threshold to the backend.
+
+// RUN: %clang -target powerpc-unknown-unknown-eabi -G 0 %s -### -o %t.o 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-SDATA0 %s
+// RUN: %clang -target powerpc-unknown-unknown-eabi -G 8 %s -### -o %t.o 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-SDATA8 %s
+
+// CHECK-SDATA0: "-mllvm" "-ppc-ssection-threshold=0"
+// CHECK-SDATA8: "-mllvm" "-ppc-ssection-threshold=8"