Document that Multilib flags must be actual flags

This is because -print-multi-lib depends on them being flags for correctness.

Fixes a case of this in the arm-android multilib selection logic.

llvm-svn: 302207

3 files changed, 33 insertions, 10 deletions

diff --git a/clang/include/clang/Driver/Multilib.h b/clang/include/clang/Driver/Multilib.h
index 0419186b745..bd8cd713baf 100644
--- a/clang/include/clang/Driver/Multilib.h
+++ b/clang/include/clang/Driver/Multilib.h
@@ -70,7 +70,14 @@ public:
   /// All elements begin with either '+' or '-'
   const flags_list &flags() const { return Flags; }
   flags_list &flags() { return Flags; }
+
   /// Add a flag to the flags list
+  /// \p Flag must be a flag accepted by the driver with its leading '-' removed,
+  ///     and replaced with either:
+  ///       '-' which contraindicates using this multilib with that flag
+  ///     or:
+  ///       '+' which promotes using this multilib in the presence of that flag
+  ///     otherwise '-print-multi-lib' will not emit them correctly.
   Multilib &flag(StringRef F) {
     assert(F.front() == '+' || F.front() == '-');
     Flags.push_back(F);
diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index d29d826b5f4..f1015e62eec 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -893,6 +893,8 @@ static bool isSoftFloatABI(const ArgList &Args) {
           A->getValue() == StringRef("soft"));
 }
 
+/// \p Flag must be a flag accepted by the driver with its leading '-' removed,
+//     otherwise '-print-multi-lib' will not emit them correctly.
 static void addMultilibFlag(bool Enabled, const char *const Flag,
                             std::vector<std::string> &Flags) {
   if (Enabled)
@@ -1437,17 +1439,17 @@ static void findAndroidArmMultilibs(const Driver &D,
   // Find multilibs with subdirectories like armv7-a, thumb, armv7-a/thumb.
   FilterNonExistent NonExistent(Path, "/crtbegin.o", D.getVFS());
   Multilib ArmV7Multilib = makeMultilib("/armv7-a")
-                               .flag("+armv7")
-                               .flag("-thumb");
+                               .flag("+march=armv7-a")
+                               .flag("-mthumb");
   Multilib ThumbMultilib = makeMultilib("/thumb")
-                               .flag("-armv7")
-                               .flag("+thumb");
+                               .flag("-march=armv7-a")
+                               .flag("+mthumb");
   Multilib ArmV7ThumbMultilib = makeMultilib("/armv7-a/thumb")
-                               .flag("+armv7")
-                               .flag("+thumb");
+                               .flag("+march=armv7-a")
+                               .flag("+mthumb");
   Multilib DefaultMultilib = makeMultilib("")
-                               .flag("-armv7")
-                               .flag("-thumb");
+                               .flag("-march=armv7-a")
+                               .flag("-mthumb");
   MultilibSet AndroidArmMultilibs =
       MultilibSet()
           .Either(ThumbMultilib, ArmV7Multilib,
@@ -1465,8 +1467,8 @@ static void findAndroidArmMultilibs(const Driver &D,
   bool IsArmV7Mode = (IsArmArch || IsThumbArch) &&
       (llvm::ARM::parseArchVersion(Arch) == 7 ||
        (IsArmArch && Arch == "" && IsV7SubArch));
-  addMultilibFlag(IsArmV7Mode, "armv7", Flags);
-  addMultilibFlag(IsThumbMode, "thumb", Flags);
+  addMultilibFlag(IsArmV7Mode, "march=armv7-a", Flags);
+  addMultilibFlag(IsThumbMode, "mthumb", Flags);
 
   if (AndroidArmMultilibs.select(Flags, Result.SelectedMultilib))
     Result.Multilibs = AndroidArmMultilibs;
diff --git a/clang/test/Driver/android-ndk-standalone.cpp b/clang/test/Driver/android-ndk-standalone.cpp
index 7fe6d3c3c2c..86ab85269f7 100644
--- a/clang/test/Driver/android-ndk-standalone.cpp
+++ b/clang/test/Driver/android-ndk-standalone.cpp
@@ -172,6 +172,20 @@
 // CHECK-ARMV7THUMB-NOT: "-L{{.*}}/lib/gcc/arm-linux-androideabi/4.9/../{{[^ ]*}}/lib/armv7-a"
 // CHECK-ARMV7THUMB-NOT: "-L{{.*}}/lib/gcc/arm-linux-androideabi/4.9/../{{[^ ]*}}/lib"
 // CHECK-ARMV7THUMB: "-L{{.*}}/sysroot/usr/lib"
+
+// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+// RUN:     -target arm-linux-androideabi -stdlib=libstdc++ \
+// RUN:     -march=armv7-a -mthumb \
+// RUN:     -B%S/Inputs/basic_android_ndk_tree \
+// RUN:     --sysroot=%S/Inputs/basic_android_ndk_tree/sysroot \
+// RUN:     -print-multi-lib \
+// RUN:   | FileCheck  --check-prefix=CHECK-ARM-MULTILIBS %s
+
+// CHECK-ARM-MULTILIBS:      thumb;@mthumb
+// CHECK-ARM-MULTILIBS-NEXT: armv7-a;@march=armv7-a
+// CHECK-ARM-MULTILIBS-NEXT: armv7-a/thumb;@march=armv7-a@mthumb
+// CHECK-ARM-MULTILIBS-NEXT: .;
+
 //
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     -target armv7a-none-linux-androideabi -stdlib=libstdc++ \