[driver] Improve the implementation of the -Ofast option.

Specifically, allow the flags that fall under this umbrella (i.e., -O3,
-ffast-math, and -fstrict-aliasing) to be overridden/disabled with the
individual -O[0|1|2|s|z]/-fno- flags.

This also fixes the handling of various floating point optimization
flags that are modified by -ffast-math (and thus -Ofast as well).
Part of rdar://13622687

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@180204 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Driver/Tools.cpp

@@ -1829,6 +1829,13 @@ static void SplitDebugInfo(const ToolChain &TC, Compilation &C,
   C.addCommand(new Command(JA, T, Exec, StripArgs));
 }
 
+static bool isOptimizationLevelFast(const ArgList &Args) {
+  if (Arg *A = Args.getLastArg(options::OPT_O_Group))
+    if (A->getOption().matches(options::OPT_Ofast))
+      return true;
+  return false;
+}
+
 void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                          const InputInfo &Output,
                          const InputInfoList &Inputs,
@@ -2117,7 +2124,13 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (!Args.hasFlag(options::OPT_fzero_initialized_in_bss,
                     options::OPT_fno_zero_initialized_in_bss))
     CmdArgs.push_back("-mno-zero-initialized-in-bss");
-  if (!Args.hasFlag(options::OPT_fstrict_aliasing,
+
+  bool OFastEnabled = isOptimizationLevelFast(Args);
+  // If -Ofast is the optimization level, then -fstrict-aliasing should be
+  // enabled.  This alias option is being used to simplify the hasFlag logic.
+  OptSpecifier StrictAliasingAliasOption = OFastEnabled ? options::OPT_Ofast :
+    options::OPT_fstrict_aliasing;
+  if (!Args.hasFlag(options::OPT_fstrict_aliasing, StrictAliasingAliasOption,
                     options::OPT_fno_strict_aliasing,
                     getToolChain().IsStrictAliasingDefault()))
     CmdArgs.push_back("-relaxed-aliasing");
@@ -2133,13 +2146,18 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // Handle segmented stacks.
   if (Args.hasArg(options::OPT_fsplit_stack))
     CmdArgs.push_back("-split-stacks");
+
+  // If -Ofast is the optimization level, then -ffast-math should be enabled.
+  // This alias option is being used to simplify the getLastArg logic.
+  OptSpecifier FastMathAliasOption = OFastEnabled ? options::OPT_Ofast :
+    options::OPT_ffast_math;
   
   // Handle various floating point optimization flags, mapping them to the
   // appropriate LLVM code generation flags. The pattern for all of these is to
   // default off the codegen optimizations, and if any flag enables them and no
   // flag disables them after the flag enabling them, enable the codegen
   // optimization. This is complicated by several "umbrella" flags.
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_ffinite_math_only,
                                options::OPT_fno_finite_math_only,
@@ -2149,7 +2167,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
         A->getOption().getID() != options::OPT_fno_finite_math_only &&
         A->getOption().getID() != options::OPT_fhonor_infinities)
       CmdArgs.push_back("-menable-no-infs");
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_ffinite_math_only,
                                options::OPT_fno_finite_math_only,
@@ -2162,7 +2180,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   // -fmath-errno is the default on some platforms, e.g. BSD-derived OSes.
   bool MathErrno = getToolChain().IsMathErrnoDefault();
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_fmath_errno,
                                options::OPT_fno_math_errno))
@@ -2175,7 +2193,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // entire set of LLVM optimizations, so collect them through all the flag
   // madness.
   bool AssociativeMath = false;
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_funsafe_math_optimizations,
                                options::OPT_fno_unsafe_math_optimizations,
@@ -2186,7 +2204,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
         A->getOption().getID() != options::OPT_fno_associative_math)
       AssociativeMath = true;
   bool ReciprocalMath = false;
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_funsafe_math_optimizations,
                                options::OPT_fno_unsafe_math_optimizations,
@@ -2197,7 +2215,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
         A->getOption().getID() != options::OPT_fno_reciprocal_math)
       ReciprocalMath = true;
   bool SignedZeros = true;
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_funsafe_math_optimizations,
                                options::OPT_fno_unsafe_math_optimizations,
@@ -2208,7 +2226,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
         A->getOption().getID() != options::OPT_fsigned_zeros)
       SignedZeros = false;
   bool TrappingMath = true;
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_funsafe_math_optimizations,
                                options::OPT_fno_unsafe_math_optimizations,
@@ -2224,7 +2242,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
 
   // Validate and pass through -fp-contract option. 
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_ffp_contract)) {
     if (A->getOption().getID() == options::OPT_ffp_contract) {
@@ -2235,7 +2253,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
         D.Diag(diag::err_drv_unsupported_option_argument)
           << A->getOption().getName() << Val;
       }
-    } else if (A->getOption().getID() == options::OPT_ffast_math) {
+    } else if (A->getOption().matches(options::OPT_ffast_math) ||
+               (OFastEnabled && A->getOption().matches(options::OPT_Ofast))) {
       // If fast-math is set then set the fp-contract mode to fast.
       CmdArgs.push_back(Args.MakeArgString("-ffp-contract=fast"));
     }
@@ -2246,9 +2265,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // preprocessor macros. This is distinct from enabling any optimizations as
   // these options induce language changes which must survive serialization
   // and deserialization, etc.
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, options::OPT_fno_fast_math))
-    if (A->getOption().matches(options::OPT_ffast_math))
-      CmdArgs.push_back("-ffast-math");
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
+                               options::OPT_fno_fast_math))
+      if (!A->getOption().matches(options::OPT_fno_fast_math))
+        CmdArgs.push_back("-ffast-math");
   if (Arg *A = Args.getLastArg(options::OPT_ffinite_math_only, options::OPT_fno_fast_math))
     if (A->getOption().matches(options::OPT_ffinite_math_only))
       CmdArgs.push_back("-ffinite-math-only");

lib/Frontend/CompilerInvocation.cpp

@@ -100,13 +100,6 @@ static unsigned getOptimizationLevelSize(ArgList &Args) {
   return 0;
 }
 
-static bool isOptimizationLevelFast(ArgList &Args) {
-  if (Arg *A = Args.getLastArg(options::OPT_O_Group))
-    if (A->getOption().matches(options::OPT_Ofast))
-      return true;
-  return false;
-}
-
 static void addWarningArgs(ArgList &Args, std::vector<std::string> &Warnings) {
   for (arg_iterator I = Args.filtered_begin(OPT_W_Group),
          E = Args.filtered_end(); I != E; ++I) {
@@ -333,8 +326,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.ForbidGuardVariables = Args.hasArg(OPT_fforbid_guard_variables);
   Opts.UseRegisterSizedBitfieldAccess = Args.hasArg(
     OPT_fuse_register_sized_bitfield_access);
-  Opts.RelaxedAliasing = Args.hasArg(OPT_relaxed_aliasing) ||
-    isOptimizationLevelFast(Args);
+  Opts.RelaxedAliasing = Args.hasArg(OPT_relaxed_aliasing);
   Opts.StructPathTBAA = Args.hasArg(OPT_struct_path_tbaa);
   Opts.DwarfDebugFlags = Args.getLastArgValue(OPT_dwarf_debug_flags);
   Opts.MergeAllConstants = !Args.hasArg(OPT_fno_merge_all_constants);
@@ -1313,8 +1305,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   // inlining enabled.
   Opts.NoInlineDefine = !Opt || Args.hasArg(OPT_fno_inline);
 
-  Opts.FastMath = Args.hasArg(OPT_ffast_math) ||
-    isOptimizationLevelFast(Args);
+  Opts.FastMath = Args.hasArg(OPT_ffast_math);
   Opts.FiniteMathOnly = Args.hasArg(OPT_ffinite_math_only);
 
   Opts.RetainCommentsFromSystemHeaders =

test/Driver/Ofast.c

@@ -0,0 +1,20 @@
+// RUN: %clang -Ofast -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST %s
+// RUN: %clang -fno-fast-math -Ofast -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST %s
+// RUN: %clang -fno-strict-aliasing -Ofast -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST %s
+// RUN: %clang -Ofast -fno-fast-math -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST-NO-FAST-MATH %s
+// RUN: %clang -Ofast -fno-strict-aliasing -### %s 2>&1 | FileCheck -check-prefix=CHECK-OFAST-NO-STRICT-ALIASING %s
+
+// CHECK-OFAST: -cc1
+// CHECK-OFAST-NOT: -relaxed-aliasing
+// CHECK-OFAST: -ffast-math
+// CHECK-OFAST: -Ofast
+
+// CHECK-OFAST-NO-FAST-MATH: -cc1
+// CHECK-OFAST-NO-FAST-MATH-NOT: -relaxed-aliasing
+// CHECK-OFAST-NO-FAST-MATH-NOT: -ffast-math
+// CHECK-OFAST-NO-FAST-MATH: -Ofast
+
+// CHECK-OFAST-NO-STRICT-ALIASING: -cc1
+// CHECK-OFAST-NO-STRICT-ALIASING: -relaxed-aliasing
+// CHECK-OFAST-NO-STRICT-ALIASING: -ffast-math
+// CHECK-OFAST-NO-STRICT-ALIASING: -Ofast