[AArch64] Support reserving x1-7 registers.

[trong]

Summary

Reserving registers x1-7 is used to support CONFIG_ARM64_LSE_ATOMICS in Linux kernel. This change adds support for reserving registers x1 through x7.

[nickdesaulniers]

Thanks for the other half of this feature!

test/Driver/aarch64-fixed-x-register.c

35

Is it worth checking a combination of these flags together work as expected (since I think you added tests that do that to llvm)?

[trong]

Added test cases for combination of -ffixed flags.

[nickdesaulniers]

Great work Tri, thank you!

docs/ClangCommandLineReference.rst

 .. option:: -mwindows<arg>
 
 .. option:: -mx32
 
 .. option:: -mxgot, -mno-xgot
 
 AARCH64
 -------
+.. option:: -ffixed-x1
+
+Reserve the x1 register (AArch64 only)
+
+.. option:: -ffixed-x2
+
+Reserve the x2 register (AArch64 only)
+
+.. option:: -ffixed-x3
+
+Reserve the x3 register (AArch64 only)
+
+.. option:: -ffixed-x4
+
+Reserve the x4 register (AArch64 only)
+
+.. option:: -ffixed-x5
+
+Reserve the x5 register (AArch64 only)
+
+.. option:: -ffixed-x6
+
+Reserve the x6 register (AArch64 only)
+
+.. option:: -ffixed-x7
+
+Reserve the x7 register (AArch64 only)
+
 .. option:: -ffixed-x18
 
 Reserve the x18 register (AArch64 only)
 
 .. option:: -ffixed-x20
 
 Reserve the x20 register (AArch64 only)
 

include/clang/Driver/Options.td

 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 mfix_cortex_a53_835769 : Flag<["-"], "mfix-cortex-a53-835769">,
   Group<m_aarch64_Features_Group>,
   HelpText<"Workaround Cortex-A53 erratum 835769 (AArch64 only)">;
 def mno_fix_cortex_a53_835769 : Flag<["-"], "mno-fix-cortex-a53-835769">,
   Group<m_aarch64_Features_Group>,
   HelpText<"Don't workaround Cortex-A53 erratum 835769 (AArch64 only)">;
-def ffixed_x18 : Flag<["-"], "ffixed-x18">, Group<m_aarch64_Features_Group>,
-  HelpText<"Reserve the x18 register (AArch64 only)">;
-def ffixed_x20 : Flag<["-"], "ffixed-x20">, Group<m_aarch64_Features_Group>,
-  HelpText<"Reserve the x20 register (AArch64 only)">;
+foreach i = {1-7,18,20} in
+  def ffixed_x#i : Flag<["-"], "ffixed-x"#i>, Group<m_aarch64_Features_Group>,
+    HelpText<"Reserve the "#i#" register (AArch64 only)">;
 
 def msimd128 : Flag<["-"], "msimd128">, Group<m_wasm_Features_Group>;
 def mno_simd128 : Flag<["-"], "mno-simd128">, Group<m_wasm_Features_Group>;
 def mnontrapping_fptoint : Flag<["-"], "mnontrapping-fptoint">, Group<m_wasm_Features_Group>;
 def mno_nontrapping_fptoint : Flag<["-"], "mno-nontrapping-fptoint">, Group<m_wasm_Features_Group>;
 def msign_ext : Flag<["-"], "msign-ext">, Group<m_wasm_Features_Group>;
 def mno_sign_ext : Flag<["-"], "mno-sign-ext">, Group<m_wasm_Features_Group>;
 def mexception_handing : Flag<["-"], "mexception-handling">, Group<m_wasm_Features_Group>;

lib/Driver/ToolChains/Arch/AArch64.cpp

else
       Features.push_back("-crc");
   }
 
   if (Arg *A = Args.getLastArg(options::OPT_mno_unaligned_access,
                                options::OPT_munaligned_access))
     if (A->getOption().matches(options::OPT_mno_unaligned_access))
       Features.push_back("+strict-align");
 
+  if (Args.hasArg(options::OPT_ffixed_x1))
+    Features.push_back("+reserve-x1");
+
+  if (Args.hasArg(options::OPT_ffixed_x2))
+    Features.push_back("+reserve-x2");
+
+  if (Args.hasArg(options::OPT_ffixed_x3))
+    Features.push_back("+reserve-x3");
+
+  if (Args.hasArg(options::OPT_ffixed_x4))
+    Features.push_back("+reserve-x4");
+
+  if (Args.hasArg(options::OPT_ffixed_x5))
+    Features.push_back("+reserve-x5");
+
+  if (Args.hasArg(options::OPT_ffixed_x6))
+    Features.push_back("+reserve-x6");
+
+  if (Args.hasArg(options::OPT_ffixed_x7))
+    Features.push_back("+reserve-x7");
+
   if (Args.hasArg(options::OPT_ffixed_x18))
     Features.push_back("+reserve-x18");
 
   if (Args.hasArg(options::OPT_ffixed_x20))
     Features.push_back("+reserve-x20");
 
   if (Args.hasArg(options::OPT_mno_neg_immediates))
     Features.push_back("+no-neg-immediates");
 }

test/Driver/aarch64-fixed-x-register.c

+// RUN: %clang -target aarch64-none-gnu -ffixed-x1 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X1 < %t %s
+// CHECK-FIXED-X1: "-target-feature" "+reserve-x1"
+
+// RUN: %clang -target aarch64-none-gnu -ffixed-x2 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X2 < %t %s
+// CHECK-FIXED-X2: "-target-feature" "+reserve-x2"
+
+// RUN: %clang -target aarch64-none-gnu -ffixed-x3 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X3 < %t %s
+// CHECK-FIXED-X3: "-target-feature" "+reserve-x3"
+
+// RUN: %clang -target aarch64-none-gnu -ffixed-x4 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X4 < %t %s
+// CHECK-FIXED-X4: "-target-feature" "+reserve-x4"
+
+// RUN: %clang -target aarch64-none-gnu -ffixed-x5 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X5 < %t %s
+// CHECK-FIXED-X5: "-target-feature" "+reserve-x5"
+
+// RUN: %clang -target aarch64-none-gnu -ffixed-x6 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X6 < %t %s
+// CHECK-FIXED-X6: "-target-feature" "+reserve-x6"
+
+// RUN: %clang -target aarch64-none-gnu -ffixed-x7 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X7 < %t %s
+// CHECK-FIXED-X7: "-target-feature" "+reserve-x7"
+
+// RUN: %clang -target aarch64-none-gnu -ffixed-x18 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X18 < %t %s
+// CHECK-FIXED-X18: "-target-feature" "+reserve-x18"
+
+// RUN: %clang -target aarch64-none-gnu -ffixed-x20 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X20 < %t %s
+// CHECK-FIXED-X20: "-target-feature" "+reserve-x20"

test/Driver/aarch64-fixed-x18.c

-// RUN: %clang -target aarch64-none-gnu -ffixed-x18 -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-FIXED-X18 < %t %s
-
-// CHECK-FIXED-X18: "-target-feature" "+reserve-x18"

test/Driver/aarch64-fixed-x20.c

-// RUN: %clang -target aarch64-none-gnu -ffixed-x20 -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-FIXED-X20 < %t %s
-
-// CHECK-FIXED-X20: "-target-feature" "+reserve-x20"