[Clang][Driver] don't error for unsupported as options for -no-integrated-as

[nickdesaulniers]

Summary

The Linux kernel's assembler flag detection started failing after
r365703. It seems that Clang was erroring for -Wa, flags that it did
not support (good), but even doing so when using -no-integrated-as
(bad).

Reported-by: Nathan Chancellor <[e-mail]>
Link: https://github.com/ClangBuiltLinux/linux/issues/598

[srhines]

s/integrates/integrated in the title, but otherwise this looks good.

[rnk]

I don't think this is the right fix, because now I think we get this behavior that we don't want:

$ clang -E t.c -o t.i -Wa,-mbig-obj
# no warning
$ clang -E t.c -o t.i -Wa,-mbig-obj -fno-integrated-as
clang: warning: argument unused during compilation: '-Wa,-mbig-obj' [-Wunused-command-line-argument]

If we can't make those behave the same, I think we should revert to fix the Linux build and silence the warning a different way.

[rnk]

I reverted @thakis's change in rC365956, but I think in retrospect I should've just stamped your change. I was glazing over the "Integrated" part of "CollectArgsForIntegratedAssembler". Anyway, I think we should leave it alone and let him decide how to handle integrated and non-integrated assembly in a uniform way.

[thakis]

Sorry, I missed this thread (and the other one) yesterday. Thanks for sorting out my mess; I'll think about what I want to do for the reland.

[thakis]

I think https://reviews.llvm.org/D65108 is a better fix, for the reason rnk gave above. I think this one can be abandoned.

clang/lib/Driver/ToolChains/Clang.cpp

void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   // If CollectArgsForIntegratedAssembler() isn't called below, call it here
   // with a dummy args list to mark assembler flags as used even when not
   // running an assembler. Otherwise, clang would emit "argument unused"
   // warnings for assembler flags when e.g. adding "-E" to flags while debugging
   // something. That'd be somewhat inconvenient, and it's also inconsistent with
   // most other flags -- we don't warn on -ffunction-sections not being used
   // in -E mode either for example, even though it's not really used either.
-  if (!isa<AssembleJobAction>(JA)) {
+  if (!isa<AssembleJobAction>(JA) && TC.useIntegratedAs()) {
     ArgStringList DummyArgs;
     CollectArgsForIntegratedAssembler(C, Args, DummyArgs, D);
   }
 
   if (isa<AnalyzeJobAction>(JA)) {
     assert(JA.getType() == types::TY_Plist && "Invalid output type.");
     CmdArgs.push_back("-analyze");
   } else if (isa<MigrateJobAction>(JA)) {

clang/test/Driver/as-options.s

 // RUN:   | FileCheck --check-prefix=WARN --allow-empty %s
 // RUN: %clang -Wa,-mbig-obj -target i386-pc-windows -E \
 // RUN:   -o /dev/null -x c++ %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARN --allow-empty %s
 // RUN: %clang -Wa,-mbig-obj -target i386-pc-windows -E \
 // RUN:   -o /dev/null -x assembler-with-cpp %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARN --allow-empty %s
 // WARN-NOT: unused
+
+// Test that unsupported arguments do not cause errors when -no-integrated-as
+// is set.
+// RUN: %clang -Wa,-mno-warn-deprecated -no-integrated-as %s -S \
+// RUN:   -Wno-unused-command-line-argument 2>&1 \
+// RUN:   | FileCheck --check-prefix=NOERROR --allow-empty %s
+// NOERROR-NOT: error: unsupported argument '-mno-warn-deprecated' to option 'Wa,'