Silence backend complaints on x86 Android

[george.burgess.iv]

Summary

r364352 started passing a new target-feature for builds with an Android x86 target. On master, this results in 'warnings' from the backend:

$ echo 'int main() {}' | llvm/clean/build/release/bin/clang++ --target=x86_64-linux-android -c -x c++ - -o /dev/null
'+mcx16' is not a recognized feature for this target (ignoring feature)
'+mcx16' is not a recognized feature for this target (ignoring feature)
'+mcx16' is not a recognized feature for this target (ignoring feature)
$

From context, my best guess is that this was just a little typo. Unsure if this is the right fix (and if it is the right fix, if we want more testing around this). Thoughts appreciated :)

[compnerd]

That is indeed a typo. I somehow ended up copying the driver flag instead of the feature flag. Thanks for fixing this!

I suppose that we could actually make the unknown features a hard error (use of the frontend is unsupported, users should be using the driver, which should always have the correct value). That seems beyond the scope of the actual fix though, lets get this fixed first :-)

[george.burgess.iv]

SGTM. Thanks for the review!

clang/lib/Driver/ToolChains/Arch/X86.cpp

void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple,
   }
 
   const llvm::Triple::ArchType ArchType = Triple.getArch();
   // Add features to be compatible with gcc for Android.
   if (Triple.isAndroid()) {
     if (ArchType == llvm::Triple::x86_64) {
       Features.push_back("+sse4.2");
       Features.push_back("+popcnt");
-      Features.push_back("+mcx16");
+      Features.push_back("+cx16");
     } else
       Features.push_back("+ssse3");
   }
 
   // Translate the high level `-mretpoline` flag to the specific target feature
   // flags. We also detect if the user asked for retpoline external thunks but
   // failed to ask for retpolines themselves (through any of the different
   // flags). This is a bit hacky but keeps existing usages working. We should

clang/test/Driver/clang-translation.c

 
 // RUN: %clang -target x86_64-linux-android -### -S %s 2>&1 \
 // RUN:        --sysroot=%S/Inputs/basic_android_tree/sysroot \
 // RUN:   | FileCheck --check-prefix=ANDROID-X86_64 %s
 // ANDROID-X86_64: clang
 // ANDROID-X86_64: "-target-cpu" "x86-64"
 // ANDROID-X86_64: "-target-feature" "+sse4.2"
 // ANDROID-X86_64: "-target-feature" "+popcnt"
-// ANDROID-X86_64: "-target-feature" "+mcx16"
+// ANDROID-X86_64: "-target-feature" "+cx16"
 
 // RUN: %clang -target mips-linux-gnu -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=MIPS %s
 // MIPS: clang
 // MIPS: "-cc1"
 // MIPS: "-target-cpu" "mips32r2"
 // MIPS: "-mfloat-abi" "hard"