[ARM64] Enable alignment control option in front-end for ARM64 - Clang.

[kevin.qin]

Summary

Hi Tim and other reviewers,

This patch is to get "-mno-unaligned-access" and "-munaligned-access" work in front-end for ARM64 target.

One thing worth to mention is, as ARM and ARM64 shared same command option in front end, does it need to share same command option in backend? If we decide to do this, the opt option "arm-strict-align" and "arm64-strict-align" would be combined to a single opt option("arm-strict-align" for example) which is shared in two backends. My question is, is it necessary to do this? And if we want do this, how to share opt object between two backends in a good way? If there is any other idea around this, please let me know. Thanks.

[t.p.northover]

Hi Kevin,

I think this looks reasonable, given current implementations. It might be better to combine into a completely generic backend "strict-align" option, particularly if more targets come along wanting the functionality. But I'm not really sure where such a thing should live.

Cheers.

Tim.

include/clang/Driver/Options.td

 def mno_sha : Flag<["-"], "mno-sha">, Group<m_x86_Features_Group>;
 
 def munaligned_access : Flag<["-"], "munaligned-access">, Group<m_arm_Features_Group>,
-  HelpText<"Allow memory accesses to be unaligned (ARM only)">;
+  HelpText<"Allow memory accesses to be unaligned (AArch32/AArch64 only)">;
 def mno_unaligned_access : Flag<["-"], "mno-unaligned-access">, Group<m_arm_Features_Group>,
-  HelpText<"Force all memory accesses to be aligned (ARM only)">;
+  HelpText<"Force all memory accesses to be aligned (AArch32/AArch64 only)">;
 def mstrict_align : Flag<["-"], "mstrict-align">, Alias<mno_unaligned_access>, Flags<[CC1Option,HelpHidden]>,
-  HelpText<"Force all memory accesses to be aligned (ARM only, same as mno-unaligned-access)">;
+  HelpText<"Force all memory accesses to be aligned (AArch64 only, same as mno-unaligned-access)">;
 def mno_thumb : Flag<["-"], "mno-thumb">, Group<m_arm_Features_Group>;
 def mrestrict_it: Flag<["-"], "mrestrict-it">, Group<m_arm_Features_Group>,
   HelpText<"Disallow generation of deprecated IT blocks for ARMv8. It is on by default for ARMv8 Thumb mode.">;

lib/Driver/Tools.cpp

                                  options::OPT_munaligned_access)) {
       if (A->getOption().matches(options::OPT_mno_unaligned_access)) {
         CmdArgs.push_back("-backend-option");
-        CmdArgs.push_back("-arm-strict-align");
+        if (getToolChain().getTriple().getArch() == llvm::Triple::arm64 ||
+            getToolChain().getTriple().getArch() == llvm::Triple::arm64_be)
+          CmdArgs.push_back("-arm64-strict-align");
+        else
+          CmdArgs.push_back("-arm-strict-align");
       } else {
         CmdArgs.push_back("-backend-option");
-        CmdArgs.push_back("-arm-no-strict-align");
+        if (getToolChain().getTriple().getArch() == llvm::Triple::arm64 ||
+            getToolChain().getTriple().getArch() == llvm::Triple::arm64_be)
+          CmdArgs.push_back("-arm64-no-strict-align");
+        else
+          CmdArgs.push_back("-arm-no-strict-align");
       }
     }
   }

test/Driver/arm-alignment.c

 // RUN: %clang -target arm-none-gnueabi -munaligned-access -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-UNALIGNED < %t %s
+// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM < %t %s
 
 // RUN: %clang -target arm-none-gnueabi -mstrict-align -munaligned-access -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-UNALIGNED < %t %s
+// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM < %t %s
 
 // RUN: %clang -target arm-none-gnueabi -mno-unaligned-access -munaligned-access -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-UNALIGNED < %t %s
+// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM < %t %s
 
-// CHECK-UNALIGNED: "-backend-option" "-arm-no-strict-align"
+// RUN: %clang -target arm64-none-gnueabi -munaligned-access -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM64 < %t %s
+
+// RUN: %clang -target arm64-none-gnueabi -mstrict-align -munaligned-access -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM64 < %t %s
+
+// RUN: %clang -target arm64-none-gnueabi -mno-unaligned-access -munaligned-access -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM64 < %t %s
+
+// CHECK-UNALIGNED-ARM: "-backend-option" "-arm-no-strict-align"
+// CHECK-UNALIGNED-ARM64: "-backend-option" "-arm64-no-strict-align"
 
 
 // RUN: %clang -target arm-none-gnueabi -mno-unaligned-access -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-ALIGNED < %t %s
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
 
 // RUN: %clang -target arm-none-gnueabi -mstrict-align -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-ALIGNED < %t %s
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
 
 // RUN: %clang -target arm-none-gnueabi -munaligned-access -mno-unaligned-access -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-ALIGNED < %t %s
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
 
 // RUN: %clang -target arm-none-gnueabi -munaligned-access -mstrict-align -### %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-ALIGNED < %t %s
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
+
+// RUN: %clang -target arm64-none-gnueabi -mno-unaligned-access -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM64 < %t %s
+
+// RUN: %clang -target arm64-none-gnueabi -mstrict-align -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM64 < %t %s
+
+// RUN: %clang -target arm64-none-gnueabi -munaligned-access -mno-unaligned-access -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM64 < %t %s
+
+// RUN: %clang -target arm64-none-gnueabi -munaligned-access -mstrict-align -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM64 < %t %s
 
-// CHECK-ALIGNED: "-backend-option" "-arm-strict-align"
+// CHECK-ALIGNED-ARM: "-backend-option" "-arm-strict-align"
+// CHECK-ALIGNED-ARM64: "-backend-option" "-arm64-strict-align"