[X86] Support -mlong-double-80

Add an option group for all of the -mlong-double-* options and make
-mlong-double-80 restore the default long double behavior for X86.  The
motivations are that GNU accepts the -mlong-double-80 option and that complex
Makefiles often need a way of undoing earlier options. Prior to this commit, if
one chooses 64-bit or 128-bit long double for X86, there is no way to undo that
choice and restore the 80-bit behavior.

Differential Revision: https://reviews.llvm.org/D66055

llvm-svn: 369152

3 files changed, 18 insertions, 7 deletions

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 0f2c314a337..baf7219aba9 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2040,9 +2040,14 @@ def malign_jumps_EQ : Joined<["-"], "malign-jumps=">, Group<clang_ignored_m_Grou
 def mfancy_math_387 : Flag<["-"], "mfancy-math-387">, Group<clang_ignored_m_Group>;
 def mlong_calls : Flag<["-"], "mlong-calls">, Group<m_Group>,
   HelpText<"Generate branches with extended addressability, usually via indirect jumps.">;
-def mlong_double_64 : Flag<["-"], "mlong-double-64">, Group<f_Group>, Flags<[CC1Option]>,
+def LongDouble_Group : OptionGroup<"<LongDouble group>">, Group<m_Group>,
+  DocName<"Long double flags">,
+  DocBrief<[{Selects the long double implementation}]>;
+def mlong_double_64 : Flag<["-"], "mlong-double-64">, Group<LongDouble_Group>, Flags<[CC1Option]>,
   HelpText<"Force long double to be 64 bits">;
-def mlong_double_128 : Flag<["-"], "mlong-double-128">, Group<f_Group>, Flags<[CC1Option]>,
+def mlong_double_80 : Flag<["-"], "mlong-double-80">, Group<LongDouble_Group>, Flags<[CC1Option]>,
+  HelpText<"Force long double to be 80 bits, padded to 128 bits for storage">;
+def mlong_double_128 : Flag<["-"], "mlong-double-128">, Group<LongDouble_Group>, Flags<[CC1Option]>,
   HelpText<"Force long double to be 128 bits">;
 def mno_long_calls : Flag<["-"], "mno-long-calls">, Group<m_Group>,
   HelpText<"Restore the default behaviour of not generating long calls">;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 2e9ccca4b29..11f75b68747 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4057,11 +4057,13 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   RenderFloatingPointOptions(TC, D, OFastEnabled, Args, CmdArgs);
 
-  if (Arg *A = Args.getLastArg(options::OPT_mlong_double_64,
-                               options::OPT_mlong_double_128)) {
+  if (Arg *A = Args.getLastArg(options::OPT_LongDouble_Group)) {
     if (TC.getArch() == llvm::Triple::x86 ||
-        TC.getArch() == llvm::Triple::x86_64 ||
-        TC.getArch() == llvm::Triple::ppc || TC.getTriple().isPPC64())
+        TC.getArch() == llvm::Triple::x86_64)
+      A->render(Args, CmdArgs);
+    else if ((TC.getArch() == llvm::Triple::ppc ||
+              TC.getArch() == TC.getTriple().isPPC64()) &&
+             (A->getOption().getID() != options::OPT_mlong_double_80))
       A->render(Args, CmdArgs);
     else
       D.Diag(diag::err_drv_unsupported_opt_for_target)
diff --git a/clang/test/Driver/mlong-double-128.c b/clang/test/Driver/mlong-double-128.c
index ae76265a3b3..d4c12dbe26e 100644
--- a/clang/test/Driver/mlong-double-128.c
+++ b/clang/test/Driver/mlong-double-128.c
@@ -2,10 +2,14 @@
 // RUN: %clang -target powerpc64-pc-freebsd12 -c -### %s -mlong-double-128 2>&1 | FileCheck %s
 // RUN: %clang -target powerpc64le-linux-musl -c -### %s -mlong-double-128 2>&1 | FileCheck %s
 // RUN: %clang -target i686-linux-gnu -c -### %s -mlong-double-128 2>&1 | FileCheck %s
-// RUN: %clang -target x86_64-linux-musl -c -### %s -mlong-double-128 2>&1 | FileCheck %s
+
+// RUN: %clang -target x86_64-linux-musl -c -### %s -mlong-double-128 -mlong-double-80 2>&1 | FileCheck --implicit-check-not=-mlong-double- /dev/null
+// RUN: %clang -target x86_64-linux-musl -c -### %s -mlong-double-80 -mlong-double-128 2>&1 | FileCheck %s
 
 // CHECK: "-mlong-double-128"
 
 // RUN: %clang -target aarch64 -c -### %s -mlong-double-128 2>&1 | FileCheck --check-prefix=ERR %s
+// RUN: %clang -target powerpc -c -### %s -mlong-double-80 2>&1 | FileCheck --check-prefix=ERR2 %s
 
 // ERR: error: unsupported option '-mlong-double-128' for target 'aarch64'
+// ERR2: error: unsupported option '-mlong-double-80' for target 'powerpc-linux-musl'