[ARM] Add hardware build attributes in assembler

This passes an option to the ARM assembly parser to emit build
attributes for the hardware selected by command line options, when
assembling an assembly file.

This is not enabled for C/C++, as this would result in duplicate build
attribute directives being emitted in each inline assembly block, when
emitting assembly.

This also adds an option to allow disabling this behaviour for assembly
files, for users who were relying on the old behaviour.

Differential revision: https://reviews.llvm.org/D31813

llvm-svn: 300550

3 files changed, 35 insertions, 0 deletions

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 36b24a02b2f..c6c9d5d8891 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1646,6 +1646,8 @@ def march_EQ : Joined<["-"], "march=">, Group<m_Group>;
 def masm_EQ : Joined<["-"], "masm=">, Group<m_Group>, Flags<[DriverOption]>;
 def mcmodel_EQ : Joined<["-"], "mcmodel=">, Group<m_Group>;
 def mimplicit_it_EQ : Joined<["-"], "mimplicit-it=">, Group<m_Group>;
+def mdefault_build_attributes : Joined<["-"], "mdefault-build-attributes">, Group<m_Group>;
+def mno_default_build_attributes : Joined<["-"], "mno-default-build-attributes">, Group<m_Group>;
 def mconstant_cfstrings : Flag<["-"], "mconstant-cfstrings">, Group<clang_ignored_m_Group>;
 def mconsole : Joined<["-"], "mconsole">, Group<m_Group>, Flags<[DriverOption]>;
 def mwindows : Joined<["-"], "mwindows">, Group<m_Group>, Flags<[DriverOption]>;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index f8eeeb4eef6..4259b629728 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4996,6 +4996,19 @@ void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
   case llvm::Triple::x86_64:
     AddX86TargetArgs(Args, CmdArgs);
     break;
+
+  case llvm::Triple::arm:
+  case llvm::Triple::armeb:
+  case llvm::Triple::thumb:
+  case llvm::Triple::thumbeb:
+    // This isn't in AddARMTargetArgs because we want to do this for assembly
+    // only, not C/C++.
+    if (Args.hasFlag(options::OPT_mdefault_build_attributes,
+                     options::OPT_mno_default_build_attributes, true)) {
+        CmdArgs.push_back("-mllvm");
+        CmdArgs.push_back("-arm-add-build-attributes");
+    }
+    break;
   }
 
   // Consume all the warning flags. Usually this would be handled more
diff --git a/clang/test/Driver/arm-default-build-attributes.s b/clang/test/Driver/arm-default-build-attributes.s
new file mode 100644
index 00000000000..b651fbb6c9f
--- /dev/null
+++ b/clang/test/Driver/arm-default-build-attributes.s
@@ -0,0 +1,20 @@
+// Enabled by default for assembly
+// RUN: %clang -target armv7--none-eabi -### %s 2>&1 \
+// RUN:    | FileCheck %s -check-prefix CHECK-ENABLED
+
+// Can be forced on or off for assembly.
+// RUN: %clang -target armv7--none-eabi -### %s 2>&1 -mno-default-build-attributes \
+// RUN:    | FileCheck %s -check-prefix CHECK-DISABLED
+// RUN: %clang -target armv7--none-eabi -### %s 2>&1 -mdefault-build-attributes \
+// RUN:    | FileCheck %s -check-prefix CHECK-ENABLED
+
+// Option ignored C/C++ (since we always emit hardware and ABI build attributes
+// during codegen).
+// RUN: %clang -target armv7--none-eabi -### -x c %s -mdefault-build-attributes -verify 2>&1 \
+// RUN:    | FileCheck %s -check-prefix CHECK-DISABLED
+// RUN: %clang -target armv7--none-eabi -### -x c++ %s -mdefault-build-attributes -verify 2>&1 \
+// RUN:    | FileCheck %s -check-prefix CHECK-DISABLED
+
+// CHECK-DISABLED-NOT: "-arm-add-build-attributes"
+// CHECK-ENABLED: "-arm-add-build-attributes"
+// expected-warning {{argument unused during compilation: '-mno-default-build-attributes'}}