[PATCH] [ARM] Add -fpu=none driver option

[Amara Emerson]

Hi t.p.northover,

Hi,

This change adds an -mfpu=none option for ARM, which disables all VFP and NEON subtarget features. To prevent the use of fpu=none causing warnings on AArch64 due to unknown features, I've split getFPUFeatures() into separate ARM and AArch64 versions.

Review appreciated.

http://llvm-reviews.chandlerc.com/D1786

Files:
  lib/Driver/Tools.cpp
  test/Driver/arm-mfpu.c

Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -573,8 +573,36 @@
 //
 // FIXME: Centralize feature selection, defaulting shouldn't be also in the
 // frontend target.
-static void getFPUFeatures(const Driver &D, const Arg *A, const ArgList &Args,
-                           std::vector<const char *> &Features) {
+static void getAArch64FPUFeatures(const Driver &D, const Arg *A,
+                                  const ArgList &Args,
+                                  std::vector<const char *> &Features) {
+  StringRef FPU = A->getValue();
+  if (FPU == "fp-armv8") {
+    Features.push_back("+fp-armv8");
+  } else if (FPU == "neon-fp-armv8") {
+    Features.push_back("+fp-armv8");
+    Features.push_back("+neon");
+  } else if (FPU == "crypto-neon-fp-armv8") {
+    Features.push_back("+fp-armv8");
+    Features.push_back("+neon");
+    Features.push_back("+crypto");
+  } else if (FPU == "neon") {
+    Features.push_back("+neon");
+  } else if (FPU == "none") {
+    Features.push_back("-fp-armv8");
+    Features.push_back("-crypto");
+    Features.push_back("-neon");
+  } else
+    D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
+}
+
+// Handle -mfpu=.
+//
+// FIXME: Centralize feature selection, defaulting shouldn't be also in the
+// frontend target.
+static void getARMFPUFeatures(const Driver &D, const Arg *A,
+                              const ArgList &Args,
+                              std::vector<const char *> &Features) {
   StringRef FPU = A->getValue();
 
   // Set the target features based on the FPU.
@@ -603,6 +631,13 @@
     Features.push_back("+fp-armv8");
   } else if (FPU == "neon") {
     Features.push_back("+neon");
+  } else if (FPU == "none") {
+    Features.push_back("-vfp2");
+    Features.push_back("-vfp3");
+    Features.push_back("-vfp4");
+    Features.push_back("-fp-armv8");
+    Features.push_back("-crypto");
+    Features.push_back("-neon");
   } else
     D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
 }
@@ -704,7 +739,7 @@
 
   // Honor -mfpu=.
   if (const Arg *A = Args.getLastArg(options::OPT_mfpu_EQ))
-    getFPUFeatures(D, A, Args, Features);
+    getARMFPUFeatures(D, A, Args, Features);
 
   // Setting -msoft-float effectively disables NEON because of the GCC
   // implementation, although the same isn't true of VFP or VFP3.
@@ -1384,7 +1419,7 @@
                                      std::vector<const char *> &Features) {
   // Honor -mfpu=.
   if (const Arg *A = Args.getLastArg(options::OPT_mfpu_EQ))
-    getFPUFeatures(D, A, Args, Features);
+    getAArch64FPUFeatures(D, A, Args, Features);
 }
 
 static void getTargetFeatures(const Driver &D, const llvm::Triple &Triple,
Index: test/Driver/arm-mfpu.c
===================================================================
--- test/Driver/arm-mfpu.c
+++ test/Driver/arm-mfpu.c
@@ -61,6 +61,15 @@
 // CHECK-CRYPTO-NEON-FP-ARMV8: "-target-feature" "+crypto"
 // CHECK-CRYPTO-NEON-FP-ARMV8: "-target-feature" "+fp-armv8"
 
+// RUN: %clang -target armv8-linux-gnueabi -mfpu=none %s -### 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FP %s
+// CHECK-NO-FP: "-target-feature" "-vfp2"
+// CHECK-NO-FP: "-target-feature" "-vfp3"
+// CHECK-NO-FP: "-target-feature" "-vfp4"
+// CHECK-NO-FP: "-target-feature" "-fp-armv8"
+// CHECK-NO-FP: "-target-feature" "-crypto"
+// CHECK-NO-FP: "-target-feature" "-neon"
+
 // RUN: %clang -target arm-linux-gnueabihf %s -### 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-HF %s
 // CHECK-HF: "-target-cpu" "arm1136jf-s"
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