ARM: Error out if float-ab=hard and abi=apcs-gnu on macho platforms

[ahatanak]

Summary

This patch corrects http://reviews.llvm.org/D12155, which didn't take into account the fact that aapcs ABI can be selected on darwin platforms. The new patch errors out only when the ABI is APCS and the float-abi is hard.

[vsk]

Yep, this looks fine. Out of curiosity, what happens if we permit the MachO + !useAAPCS + FloatABI=hard case?

[ahatanak]

float-abi=hard has no effect on the backend code-generation if the ABI is APCS, meaning GPRs will be used to pass floating point arguments. This patch makes changes to the driver so that the error is detected in the front-end rather than silently ignoring the option in the backend.

[vsk]

Done in clang/r246054

lib/Driver/Tools.cpp

static void checkARMCPUName(const Driver &D, const Arg *A, const ArgList &Args,
                             llvm::StringRef CPUName, llvm::StringRef ArchName,
                             const llvm::Triple &Triple) {
   std::string CPU = arm::getARMTargetCPU(CPUName, ArchName, Triple);
   std::string Arch = arm::getARMArch(ArchName, Triple);
   if (strcmp(arm::getLLVMArchSuffixForARM(CPU, Arch), "") == 0)
     D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
 }
 
+static bool useAAPCSForMachO(const llvm::Triple &T) {
+  // The backend is hardwired to assume AAPCS for M-class processors, ensure
+  // the frontend matches that.
+  return T.getEnvironment() == llvm::Triple::EABI ||
+         T.getOS() == llvm::Triple::UnknownOS || isARMMProfile(T);
+}
+
 // Select the float ABI as determined by -msoft-float, -mhard-float, and
 // -mfloat-abi=.
 StringRef tools::arm::getARMFloatABI(const Driver &D, const ArgList &Args,
                                      const llvm::Triple &Triple) {
   StringRef FloatABI;
   if (Arg *A =
           Args.getLastArg(options::OPT_msoft_float, options::OPT_mhard_float,
                           options::OPT_mfloat_abi_EQ)) {
     if (A->getOption().matches(options::OPT_msoft_float))
       FloatABI = "soft";
     else if (A->getOption().matches(options::OPT_mhard_float))
       FloatABI = "hard";
     else {
       FloatABI = A->getValue();
       if (FloatABI != "soft" && FloatABI != "softfp" && FloatABI != "hard") {
         D.Diag(diag::err_drv_invalid_mfloat_abi) << A->getAsString(Args);
         FloatABI = "soft";
       }
     }
+
+    // It is incorrect to select hard float ABI on MachO platforms if the ABI is
+    // "apcs-gnu".
+    if (Triple.isOSBinFormatMachO() && !useAAPCSForMachO(Triple) &&
+        FloatABI == "hard")
+      D.Diag(diag::err_drv_unsupported_opt_for_target) << A->getAsString(Args)
+                                                       << Triple.getArchName();
   }
 
   // If unspecified, choose the default based on the platform.
   if (FloatABI.empty()) {
     switch (Triple.getOS()) {
     case llvm::Triple::Darwin:
     case llvm::Triple::MacOSX:
     case llvm::Triple::IOS: {
void Clang::AddARMTargetArgs(const ArgList &Args, ArgStringList &CmdArgs,
   // Select the ABI to use.
   //
   // FIXME: Support -meabi.
   // FIXME: Parts of this are duplicated in the backend, unify this somehow.
   const char *ABIName = nullptr;
   if (Arg *A = Args.getLastArg(options::OPT_mabi_EQ)) {
     ABIName = A->getValue();
   } else if (Triple.isOSBinFormatMachO()) {
-    // The backend is hardwired to assume AAPCS for M-class processors, ensure
-    // the frontend matches that.
-    if (Triple.getEnvironment() == llvm::Triple::EABI ||
-        Triple.getOS() == llvm::Triple::UnknownOS || isARMMProfile(Triple)) {
+    if (useAAPCSForMachO(Triple)) {
       ABIName = "aapcs";
     } else {
       ABIName = "apcs-gnu";
     }
   } else if (Triple.isOSWindows()) {
     // FIXME: this is invalid for WindowsCE
     ABIName = "aapcs";
   } else {

test/Driver/arm-float-abi.c

+// RUN: not %clang %s -target armv7-apple-ios -mfloat-abi=hard 2>&1 | FileCheck -check-prefix=ARMV7-ERROR %s
+// RUN: %clang %s -target armv7-apple-ios -mfloat-abi=softfp -### 2>&1 | FileCheck -check-prefix=NOERROR %s
+// RUN: %clang %s -arch armv7 -target thumbv7-apple-darwin-eabi -mfloat-abi=hard -### 2>&1 | FileCheck -check-prefix=NOERROR %s
+
+// ARMV7-ERROR: unsupported option '-mfloat-abi=hard' for target 'thumbv7'
+// NOERROR-NOT: unsupported option