[Driver] Default all Android ARM targets to NEON.

[danalbert]

Summary

There are an insignificant number of ARM Android devices that don't
support NEON. Default to using NEON since that will improve
performance on the majority of devices. Users that need to target
non-NEON devices can still explicitly disable NEON.

[efriedma]

The official documentation still says "Your app must perform runtime detection to confirm that NEON-capable machine code can be run on the target device" (https://developer.android.com/ndk/guides/cpu-arm-neon#runtime_detection). Is that wrong?

[danalbert]

In D58153#1395601, @efriedma wrote:

The official documentation still says "Your app must perform runtime detection to confirm that NEON-capable machine code can be run on the target device" (https://developer.android.com/ndk/guides/cpu-arm-neon#runtime_detection). Is that wrong?

I'll update those docs when this change lands in the NDK (thanks for spotting that). Since there are so few devices affected by this we're instead advising developers to blacklist these CPUs or explicitly set their -mfpu to vfp3-d16 if they want to continue supporting those devices.

cfe/trunk/lib/Driver/ToolChains/Arch/ARM.cpp

if (WaFPU) {
     if (FPUArg)
       D.Diag(clang::diag::warn_drv_unused_argument)
           << FPUArg->getAsString(Args);
     getARMFPUFeatures(D, WaFPU, Args, StringRef(WaFPU->getValue()).substr(6),
                       Features);
   } else if (FPUArg) {
     getARMFPUFeatures(D, FPUArg, Args, FPUArg->getValue(), Features);
   } else if (Triple.isAndroid() && getARMSubArchVersionNumber(Triple) >= 7) {
-    // Android mandates minimum FPU requirements based on OS version.
-    const char *AndroidFPU =
-        Triple.isAndroidVersionLT(23) ? "vfpv3-d16" : "neon";
+    const char *AndroidFPU = "neon";
     if (!llvm::ARM::getFPUFeatures(llvm::ARM::parseFPU(AndroidFPU), Features))
       D.Diag(clang::diag::err_drv_clang_unsupported)
           << std::string("-mfpu=") + AndroidFPU;
   }
 
   // Honor -mhwdiv=. ClangAs gives preference to -Wa,-mhwdiv=.
   const Arg *HDivArg = Args.getLastArg(options::OPT_mhwdiv_EQ);
   if (WaHDiv) {

cfe/trunk/test/Driver/arm-mfpu.c

 // CHECK-ARM5-ANDROID-FP-DEFAULT: "-target-feature" "+soft-float-abi"
 // CHECK-ARM5-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+d16"
 // CHECK-ARM5-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+vfp3"
 // CHECK-ARM5-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+vfp4"
 // CHECK-ARM5-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+fp-armv8"
 // CHECK-ARM5-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+neon"
 // CHECK-ARM5-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+crypto"
 
-// RUN: %clang -target arm-linux-androideabi21 -march=armv7-a %s -### -c 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-MARCH-ARM7-ANDROID-FP %s
-// CHECK-MARCH-ARM7-ANDROID-FP-NOT: "-target-feature" "+soft-float"
-// CHECK-MARCH-ARM7-ANDROID-FP: "-target-feature" "+soft-float-abi"
-// CHECK-MARCH-ARM7-ANDROID-FP: "-target-feature" "+d16"
-// CHECK-MARCH-ARM7-ANDROID-FP: "-target-feature" "+vfp3"
-// CHECK-MARCH-ARM7-ANDROID-FP-NOT: "-target-feature" "+vfp4"
-// CHECK-MARCH-ARM7-ANDROID-FP-NOT: "-target-feature" "+fp-armv8"
-// CHECK-MARCH-ARM7-ANDROID-FP-NOT: "-target-feature" "+neon"
-// CHECK-MARCH-ARM7-ANDROID-FP-NOT: "-target-feature" "+crypto"
-
 // RUN: %clang -target armv7-linux-androideabi21 %s -### -c 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-ARM-ANDROID-L-FP-DEFAULT %s
-// CHECK-ARM-ANDROID-L-FP-DEFAULT-NOT: "-target-feature" "+soft-float"
-// CHECK-ARM-ANDROID-L-FP-DEFAULT: "-target-feature" "+soft-float-abi"
-// CHECK-ARM-ANDROID-L-FP-DEFAULT: "-target-feature" "+d16"
-// CHECK-ARM-ANDROID-L-FP-DEFAULT: "-target-feature" "+vfp3"
-// CHECK-ARM-ANDROID-L-FP-DEFAULT-NOT: "-target-feature" "+vfp4"
-// CHECK-ARM-ANDROID-L-FP-DEFAULT-NOT: "-target-feature" "+fp-armv8"
-// CHECK-ARM-ANDROID-L-FP-DEFAULT-NOT: "-target-feature" "+neon"
-// CHECK-ARM-ANDROID-L-FP-DEFAULT-NOT: "-target-feature" "+crypto"
-
-// RUN: %clang -target armv7-linux-androideabi21 -mfpu=neon %s -### -c 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-ARM-ANDROID-L-FP-NEON %s
-// CHECK-ARM-ANDROID-L-FP-NEON-NOT: "-target-feature" "+soft-float"
-// CHECK-ARM-ANDROID-L-FP-NEON: "-target-feature" "+soft-float-abi"
-// CHECK-ARM-ANDROID-L-FP-NEON: "-target-feature" "+vfp3"
-// CHECK-ARM-ANDROID-L-FP-NEON-NOT: "-target-feature" "+vfp4"
-// CHECK-ARM-ANDROID-L-FP-NEON-NOT: "-target-feature" "+fp-armv8"
-// CHECK-ARM-ANDROID-L-FP-NEON: "-target-feature" "+neon"
-// CHECK-ARM-ANDROID-L-FP-NEON-NOT: "-target-feature" "+crypto"
-
-// RUN: %clang -target armv7-linux-androideabi23 %s -### -c 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-ARM-ANDROID-M-FP-DEFAULT %s
-// CHECK-ARM-ANDROID-M-FP-DEFAULT-NOT: "-target-feature" "+soft-float"
-// CHECK-ARM-ANDROID-M-FP-DEFAULT: "-target-feature" "+soft-float-abi"
-// CHECK-ARM-ANDROID-M-FP-DEFAULT: "-target-feature" "+vfp3"
-// CHECK-ARM-ANDROID-M-FP-DEFAULT-NOT: "-target-feature" "+vfp4"
-// CHECK-ARM-ANDROID-M-FP-DEFAULT-NOT: "-target-feature" "+fp-armv8"
-// CHECK-ARM-ANDROID-M-FP-DEFAULT: "-target-feature" "+neon"
-// CHECK-ARM-ANDROID-M-FP-DEFAULT-NOT: "-target-feature" "+crypto"
-
-// RUN: %clang -target armv7-linux-androideabi23 %s -mfpu=vfp3-d16 -### -c 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-ARM-ANDROID-M-FP-D16 %s
-// CHECK-ARM-ANDROID-M-FP-D16-NOT: "-target-feature" "+soft-float"
-// CHECK-ARM-ANDROID-M-FP-D16: "-target-feature" "+soft-float-abi"
-// CHECK-ARM-ANDROID-M-FP-D16: "-target-feature" "+d16"
-// CHECK-ARM-ANDROID-M-FP-D16: "-target-feature" "+vfp3"
-// CHECK-ARM-ANDROID-M-FP-D16-NOT: "-target-feature" "+vfp4"
-// CHECK-ARM-ANDROID-M-FP-D16-NOT: "-target-feature" "+fp-armv8"
-// CHECK-ARM-ANDROID-M-FP-D16-NOT: "-target-feature" "+neon"
-// CHECK-ARM-ANDROID-M-FP-D16-NOT: "-target-feature" "+crypto"
+// RUN:   | FileCheck --check-prefix=CHECK-ARM7-ANDROID-FP-DEFAULT %s
+// CHECK-ARM7-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+soft-float"
+// CHECK-ARM7-ANDROID-FP-DEFAULT: "-target-feature" "+soft-float-abi"
+// CHECK-ARM7-ANDROID-FP-DEFAULT: "-target-feature" "+vfp3"
+// CHECK-ARM7-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+vfp4"
+// CHECK-ARM7-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+fp-armv8"
+// CHECK-ARM7-ANDROID-FP-DEFAULT: "-target-feature" "+neon"
+// CHECK-ARM7-ANDROID-FP-DEFAULT-NOT: "-target-feature" "+crypto"
+
+// RUN: %clang -target armv7-linux-androideabi21 %s -mfpu=vfp3-d16 -### -c 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-ARM7-ANDROID-FP-D16 %s
+// CHECK-ARM7-ANDROID-FP-D16-NOT: "-target-feature" "+soft-float"
+// CHECK-ARM7-ANDROID-FP-D16: "-target-feature" "+soft-float-abi"
+// CHECK-ARM7-ANDROID-FP-D16: "-target-feature" "+d16"
+// CHECK-ARM7-ANDROID-FP-D16: "-target-feature" "+vfp3"
+// CHECK-ARM7-ANDROID-FP-D16-NOT: "-target-feature" "+vfp4"
+// CHECK-ARM7-ANDROID-FP-D16-NOT: "-target-feature" "+fp-armv8"
+// CHECK-ARM7-ANDROID-FP-D16-NOT: "-target-feature" "+neon"
+// CHECK-ARM7-ANDROID-FP-D16-NOT: "-target-feature" "+crypto"