[PATCH] [AArch64] Add -mgeneral_regs_only option

[Amara Emerson]

Add support for the -mgeneral_regs_only option (in AArch64 only), which restricts LLVM to generate code using only the general purpose registers. The command line argument is already supported by AArch64 GCC.

This patch essentially replaces the existing -mfpu=none option, as -mfpu will soon be dropped entirely.

http://llvm-reviews.chandlerc.com/D2586

Files:
  docs/UsersManual.rst
  include/clang/Driver/Options.td
  lib/Driver/Tools.cpp
  test/Driver/aarch64-mfpu.c
  test/Driver/aarch64-mgeneral_regs_only.c

Index: docs/UsersManual.rst
===================================================================
--- docs/UsersManual.rst
+++ docs/UsersManual.rst
@@ -1061,6 +1061,13 @@
 
    CRC instructions are enabled by default on ARMv8.
 
+.. option:: -mgeneral_regs_only
+
+   Generate code which only uses the general purpose registers.
+
+   This option restricts the generated code to use general registers
+   only. This only applies to the AArch64 architecture.
+
 
 Controlling Size of Debug Information
 -------------------------------------
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -72,6 +72,7 @@
 def m_x86_Features_Group  : OptionGroup<"<m x86 features group>">, Group<m_Group>;
 def m_hexagon_Features_Group  : OptionGroup<"<m hexagon features group>">, Group<m_Group>;
 def m_arm_Features_Group  : OptionGroup<"<m arm features group>">, Group<m_Group>;
+def m_aarch64_Features_Group  : OptionGroup<"<m aarch64 features group>">, Group<m_Group>;
 def m_ppc_Features_Group  : OptionGroup<"<m ppc features group>">, Group<m_Group>;
 def u_Group               : OptionGroup<"<u group>">;
 
@@ -1052,6 +1053,9 @@
 def mnocrc : Flag<["-"], "mnocrc">, Group<m_arm_Features_Group>,
   HelpText<"Disallow use of CRC instructions (ARM only)">;
 
+def mgeneral_regs_only : Flag<["-"], "mgeneral_regs_only">, Group<m_aarch64_Features_Group>,
+  HelpText<"Generate code which only uses the general purpose registers (AArch64 only)">;
+
 def mvsx : Flag<["-"], "mvsx">, Group<m_ppc_Features_Group>;
 def mno_vsx : Flag<["-"], "mno-vsx">, Group<m_ppc_Features_Group>;
 def mfprnd : Flag<["-"], "mfprnd">, Group<m_ppc_Features_Group>;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -515,10 +515,6 @@
     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);
 }
@@ -1434,6 +1430,12 @@
   // Honor -mfpu=.
   if (const Arg *A = Args.getLastArg(options::OPT_mfpu_EQ))
     getAArch64FPUFeatures(D, A, Args, Features);
+
+  if (Args.getLastArg(options::OPT_mgeneral_regs_only)) {
+    Features.push_back("-fp-armv8");
+    Features.push_back("-crypto");
+    Features.push_back("-neon");
+  }
 }
 
 static void getTargetFeatures(const Driver &D, const llvm::Triple &Triple,
Index: test/Driver/aarch64-mfpu.c
===================================================================
--- test/Driver/aarch64-mfpu.c
+++ test/Driver/aarch64-mfpu.c
@@ -19,8 +19,3 @@
 // CHECK-CRYPTO-NEON-FP-ARMV8: "-target-feature" "+neon"
 // CHECK-CRYPTO-NEON-FP-ARMV8: "-target-feature" "+crypto"
 
-// RUN: %clang -target aarch64-linux-eabi -mfpu=none %s -### 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-NO-FP %s
-// CHECK-NO-FP: "-target-feature" "-fp-armv8"
-// CHECK-NO-FP: "-target-feature" "-crypto"
-// CHECK-NO-FP: "-target-feature" "-neon"
Index: test/Driver/aarch64-mgeneral_regs_only.c
===================================================================
--- /dev/null
+++ test/Driver/aarch64-mgeneral_regs_only.c
@@ -0,0 +1,7 @@
+// Test the -mgeneral_regs_only option
+
+// RUN: %clang -target aarch64-linux-eabi -mgeneral_regs_only %s -### 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FP %s
+// CHECK-NO-FP: "-target-feature" "-fp-armv8"
+// CHECK-NO-FP: "-target-feature" "-crypto"
+// CHECK-NO-FP: "-target-feature" "-neon"
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