[clang][IFS] Claiming -emit-merged-ifs in clang driver when -c is used.

[plotfi]

Summary

Sometimes it is difficult to tell when you want your compile flags to be invoked with -emit-interface-stubs -c or with -emit-interface-stubs -emit-merged-ifs. On -Werror builds -emit-interface-stubs -emit-merged-ifs -c causes build errors. I think for now we can claim -emit-merged-ifs.

[compnerd]

The commit message doesn't really explain much. Why simply consume the argument? Why not actually halt the build since this clearly is conflicting, and its unclear what the user intended.

[plotfi]

This commit is no good. I got some wrong inspiration from a lot of the code claiming random args in the driver. abandoning.

clang/lib/Driver/Driver.cpp

   if (Args.hasArg(options::OPT_emit_interface_stubs)) {
     llvm::SmallVector<phases::ID, phases::MaxNumberOfPhases> PhaseList;
     if (Args.hasArg(options::OPT_c)) {
+      // Claim -emit-merged-ifs if we aren't going to invoke llvm-ifs.
+      // The intention of -emit-merged-ifs is to force llvm-ifs to generate text
+      // instead of a ifso. Perhaps this should be inverted.
+      if (Args.hasArg(options::OPT_emit_merged_ifs))
+        Args.ClaimAllArgs(options::OPT_emit_merged_ifs);
       llvm::SmallVector<phases::ID, phases::MaxNumberOfPhases> CompilePhaseList;
       types::getCompilationPhases(types::TY_IFS_CPP, CompilePhaseList);
       llvm::copy_if(CompilePhaseList, std::back_inserter(PhaseList),

clang/test/InterfaceStubs/warnings.c

+// RUN: %clang -emit-interface-stubs -emit-merged-ifs -c %s -o - 2>&1 | FileCheck %s
+// CHECK-NOT: warning: argument unused during compilation: '-emit-merged-ifs'
+int main() {}