Fix an logic error in the clang driver preventing crtfastmath.o from linking when -Ofast is used without -ffast-math

In gcc using -Ofast forces linking of crtfastmath.o.
In the current clang crtfastmath.o is only linked when -ffast-math/-funsafe-math-optimizations passed. It can lead to performance issues, when using only -Ofast without explicit -ffast-math (I faced with it).
My patch fixes inconsistency with gcc behaviour and also introduces few tests on it.

Patch by Zinovy Nis!

Differential Revision: http://llvm-reviews.chandlerc.com/D3114

llvm-svn: 204742

6 files changed, 44 insertions, 19 deletions

diff --git a/clang/include/clang/Driver/Driver.h b/clang/include/clang/Driver/Driver.h
index 056c28549aa..044872591f5 100644
--- a/clang/include/clang/Driver/Driver.h
+++ b/clang/include/clang/Driver/Driver.h
@@ -415,6 +415,10 @@ public:
                                 bool &HadExtra);
 };
 
+/// \return True if the last defined optimization level is -Ofast.
+/// And False otherwise.
+bool isOptimizationLevelFast(const llvm::opt::ArgList &Args);
+
 } // end namespace driver
 } // end namespace clang
 
diff --git a/clang/include/clang/Driver/ToolChain.h b/clang/include/clang/Driver/ToolChain.h
index 9c7f4b52c1c..a43ee107512 100644
--- a/clang/include/clang/Driver/ToolChain.h
+++ b/clang/include/clang/Driver/ToolChain.h
@@ -311,7 +311,7 @@ public:
   /// AddFastMathRuntimeIfAvailable - If a runtime library exists that sets
   /// global flags for unsafe floating point math, add it and return true.
   ///
-  /// This checks for presence of the -ffast-math or -funsafe-math flags.
+  /// This checks for presence of the -Ofast, -ffast-math or -funsafe-math flags.
   virtual bool
   AddFastMathRuntimeIfAvailable(const llvm::opt::ArgList &Args,
                                 llvm::opt::ArgStringList &CmdArgs) const;
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index c318b60a938..5cc19f5f8e6 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -2049,3 +2049,7 @@ std::pair<unsigned, unsigned> Driver::getIncludeExcludeOptionFlagMasks() const {
 
   return std::make_pair(IncludedFlagsBitmask, ExcludedFlagsBitmask);
 }
+
+bool clang::driver::isOptimizationLevelFast(const llvm::opt::ArgList &Args) {
+  return Args.hasFlag(options::OPT_Ofast, options::OPT_O_Group, false);
+}
diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 4103914d297..9f756f7c63d 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -341,16 +341,19 @@ void ToolChain::AddCCKextLibArgs(const ArgList &Args,
 
 bool ToolChain::AddFastMathRuntimeIfAvailable(const ArgList &Args,
                                               ArgStringList &CmdArgs) const {
-  // Check if -ffast-math or -funsafe-math is enabled.
-  Arg *A = Args.getLastArg(options::OPT_ffast_math,
-                           options::OPT_fno_fast_math,
-                           options::OPT_funsafe_math_optimizations,
-                           options::OPT_fno_unsafe_math_optimizations);
-
-  if (!A || A->getOption().getID() == options::OPT_fno_fast_math ||
-      A->getOption().getID() == options::OPT_fno_unsafe_math_optimizations)
-    return false;
-
+  // Do not check for -fno-fast-math or -fno-unsafe-math when -Ofast passed
+  // (to keep the linker options consistent with gcc and clang itself).
+  if (!isOptimizationLevelFast(Args)) {
+    // Check if -ffast-math or -funsafe-math.
+    Arg *A =
+        Args.getLastArg(options::OPT_ffast_math, options::OPT_fno_fast_math,
+                        options::OPT_funsafe_math_optimizations,
+                        options::OPT_fno_unsafe_math_optimizations);
+
+    if (!A || A->getOption().getID() == options::OPT_fno_fast_math ||
+        A->getOption().getID() == options::OPT_fno_unsafe_math_optimizations)
+      return false;
+  }
   // If crtfastmath.o exists add it to the arguments.
   std::string Path = GetFilePath("crtfastmath.o");
   if (Path == "crtfastmath.o") // Not found.
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index ef3e00329dd..c90fb81f030 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2034,13 +2034,6 @@ 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;
-}
-
 /// \brief Vectorize at all optimization levels greater than 1 except for -Oz.
 static bool shouldEnableVectorizerAtOLevel(const ArgList &Args) {
   if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
diff --git a/clang/test/Driver/linux-ld.c b/clang/test/Driver/linux-ld.c
index 2d1f8ed08c0..ca390d9b3b0 100644
--- a/clang/test/Driver/linux-ld.c
+++ b/clang/test/Driver/linux-ld.c
@@ -825,7 +825,7 @@
 // CHECK-FSL-PPC64: "{{.*}}{{/|\\\\}}crtbegin.o"
 // CHECK-FSL-PPC64: "-L[[SYSROOT]]/usr/lib64/powerpc64-fsl-linux/4.6.2/../.."
 //
-// Check that crtfastmath.o is linked with -ffast-math.
+// Check that crtfastmath.o is linked with -ffast-math and with -Ofast.
 // RUN: %clang --target=x86_64-unknown-linux -### %s \
 // RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NOCRTFASTMATH %s
@@ -835,9 +835,30 @@
 // RUN: %clang --target=x86_64-unknown-linux -### %s -funsafe-math-optimizations\
 // RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-CRTFASTMATH %s
+// RUN: %clang --target=x86_64-unknown-linux -### %s -Ofast\
+// RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-CRTFASTMATH %s
+// RUN: %clang --target=x86_64-unknown-linux -### %s -Ofast -O3\
+// RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NOCRTFASTMATH %s
+// RUN: %clang --target=x86_64-unknown-linux -### %s -O3 -Ofast\
+// RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-CRTFASTMATH %s
 // RUN: %clang --target=x86_64-unknown-linux -### %s -ffast-math -fno-fast-math \
 // RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NOCRTFASTMATH %s
+// RUN: %clang --target=x86_64-unknown-linux -### %s -Ofast -fno-fast-math \
+// RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-CRTFASTMATH %s
+// RUN: %clang --target=x86_64-unknown-linux -### %s -Ofast -fno-unsafe-math-optimizations \
+// RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-CRTFASTMATH %s
+// RUN: %clang --target=x86_64-unknown-linux -### %s -fno-fast-math -Ofast  \
+// RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-CRTFASTMATH %s
+// RUN: %clang --target=x86_64-unknown-linux -### %s -fno-unsafe-math-optimizations -Ofast \
+// RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-CRTFASTMATH %s
 // We don't have crtfastmath.o in the i386 tree, use it to check that file
 // detection works.
 // RUN: %clang --target=i386-unknown-linux -### %s -ffast-math \