[Android] Default to -fno-math-errno

[pirama]

Summary

Android's libm does not set errno.

[pirama]

lib/Driver/ToolChains/Linux.cpp

913

I tried to be defensive here in case the default changes in the future. I can simplify to just return true here if that'd be simpler.

[srhines]

lib/Driver/ToolChains/Linux.cpp

913

I agree with this, since this matches the present behavior.

lib/Driver/ToolChains/Linux.h

public:
   void addLibStdCxxIncludePaths(
       const llvm::opt::ArgList &DriverArgs,
       llvm::opt::ArgStringList &CC1Args) const override;
   void AddCudaIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                           llvm::opt::ArgStringList &CC1Args) const override;
   void AddIAMCUIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                            llvm::opt::ArgStringList &CC1Args) const override;
   bool isPIEDefault() const override;
+  bool IsMathErrnoDefault() const override;
   SanitizerMask getSupportedSanitizers() const override;
   void addProfileRTLibs(const llvm::opt::ArgList &Args,
                         llvm::opt::ArgStringList &CmdArgs) const override;
   virtual std::string computeSysRoot() const;
 
   virtual std::string getDynamicLinker(const llvm::opt::ArgList &Args) const;
 
   std::vector<std::string> ExtraOpts;

lib/Driver/ToolChains/Linux.cpp

void Linux::AddIAMCUIncludeArgs(const ArgList &DriverArgs,
   }
 }
 
 bool Linux::isPIEDefault() const {
   return (getTriple().isAndroid() && !getTriple().isAndroidVersionLT(16)) ||
           getTriple().isMusl() || getSanitizerArgs().requiresPIE();
 }
 
+bool Linux::IsMathErrnoDefault() const {
+  if (getTriple().isAndroid())
+    return false;
+  return Generic_ELF::IsMathErrnoDefault();
+}
+
 SanitizerMask Linux::getSupportedSanitizers() const {
   const bool IsX86 = getTriple().getArch() == llvm::Triple::x86;
   const bool IsX86_64 = getTriple().getArch() == llvm::Triple::x86_64;
   const bool IsMIPS = getTriple().isMIPS32();
   const bool IsMIPS64 = getTriple().isMIPS64();
   const bool IsPowerPC64 = getTriple().getArch() == llvm::Triple::ppc64 ||
                            getTriple().getArch() == llvm::Triple::ppc64le;
   const bool IsAArch64 = getTriple().getArch() == llvm::Triple::aarch64 ||

test/Driver/fast-math.c

 // RUN: %clang -### -target x86_64-unknown-netbsd -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 // RUN: %clang -### -target x86_64-unknown-openbsd -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 // RUN: %clang -### -target x86_64-unknown-dragonfly -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 // RUN: %clang -### -target x86_64-fuchsia -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
+// RUN: %clang -### -target x86_64-linux-android -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 //
 // Check that -ffast-math disables -fmath-errno, and -fno-fast-math merely
 // preserves the target default. Also check various flag set operations between
 // the two flags. (Resuses above checks.)
 // RUN: %clang -### -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 // RUN: %clang -### -fmath-errno -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s