[AIX][Driver] Implement -mxcoff-build-id option.

[w2yehia]

Summary

The -mxcoff-build-id=0xHEXSTRING option is an alternative to the
--build-id=0xHEXSTRING linker option that is not currently available in
the AIX linker.

If HEXSTRING is an odd number of hex digits then a '0' character is prepended.
The characters ':' and '-' are not allowed (unlike the GNU linker option).
The given build-id will be saved in the string table of the loader section.

A subsequent commit will teach the profile runtime to read and use the embedded id.

[w2yehia]

add "<0xHEXSTRING>" to the option documentation.

[w2yehia]

add new test

[stephenpeckham]

Is there any reason to require an even number of hex digits? Or to convert the hex string to lower case?

clang/test/Driver/xcoff-build-id.c

7

You could add a test where the build id is specified with upper case hex digits to ensure they're converted successfully.

[w2yehia]

clang/test/Driver/xcoff-build-id.c

7

need to test that the -bdbg:ldrinfo linker flag we pass to the linker comes before any user specified linker options (or at least before any user specified -bdbg:ldrinfo flags)

[w2yehia]

Is there any reason to require an even number of hex digits? Or to convert the hex string to lower case?

only that's it's easier to convert ascii to number (atoi) by anyone reading the info and needing it in number form (such as the PGO runtime)

clang/test/Driver/xcoff-build-id.c

7

that's covered on line 2

[qiongsiwu1]

LGTM! Thanks!

[daltenty]

Let's document the option as well under: https://clang.llvm.org/docs/ClangCommandLineReference.html#powerpc

clang/lib/Driver/ToolChains/AIX.cpp

152

nit: there are some notes in getSpelling() about why getAsString is preferred I believe

154–158

minor nit: I find this a little more readable and it avoids the empty append

[w2yehia]

Fix bug: StringRef::lower() returns a std::string as a temporary, and Twine doesn't own the memory of the substrings.
The temporary should be used in the same C++ statement so that there's no lifetime issues.

[w2yehia]

Let's document the option as well under: https://clang.llvm.org/docs/ClangCommandLineReference.html#powerpc

I tried changing the Option group from m__Group to m_ppc_Features_Group but that causes clang/llvm to write the flag as an attribute in the IR, causing compilation issues.
Also I noticed that m_Group is a CompileOnly_Group, and so I changed the group to the more appropriate Link_Group.

clang/lib/Driver/ToolChains/AIX.cpp

152

not in this case; here's the diagnostics I get with your suggestion:

clang: error: unsupported argument 'ff' to option '-mxcoff-build-id=ff'

[daltenty]

LGTM, thanks!

clang/include/clang/Driver/Options.td

 
 defm zvector : BoolFOption<"zvector",
   LangOpts<"ZVector">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option], "Enable System z vector language extension">,
   NegFlag<SetFalse>>;
 def mzvector : Flag<["-"], "mzvector">, Alias<fzvector>;
 def mno_zvector : Flag<["-"], "mno-zvector">, Alias<fno_zvector>;
 
+def mxcoff_build_id_EQ : Joined<["-"], "mxcoff-build-id=">, Group<Link_Group>, MetaVarName<"<0xHEXSTRING>">,
+  HelpText<"On AIX, request creation of a build-id string, \"0xHEXSTRING\", in the string table of the loader section inside the linked binary">;
 def mignore_xcoff_visibility : Flag<["-"], "mignore-xcoff-visibility">, Group<m_Group>,
 HelpText<"Not emit the visibility attribute for asm in AIX OS or give all symbols 'unspecified' visibility in XCOFF object file">,
   Flags<[CC1Option]>;
 defm backchain : BoolOption<"m", "backchain",
   CodeGenOpts<"Backchain">, DefaultFalse,
   PosFlag<SetTrue, [], "Link stack frames through backchain on System Z">,
   NegFlag<SetFalse>, BothFlags<[NoXarchOption,CC1Option]>>, Group<m_Group>;
 

clang/lib/Driver/ToolChains/AIX.cpp

if (Args.hasFlag(options::OPT_fprofile_arcs, options::OPT_fno_profile_arcs,
        Args.hasFlag(options::OPT_fcs_profile_generate,
                     options::OPT_fno_profile_generate, false) ||
        Args.hasFlag(options::OPT_fcs_profile_generate_EQ,
                     options::OPT_fno_profile_generate, false) ||
        Args.hasArg(options::OPT_fcreate_profile) ||
        Args.hasArg(options::OPT_coverage))
     CmdArgs.push_back("-bdbg:namedsects:ss");
 
+  if (Arg *A =
+          Args.getLastArg(clang::driver::options::OPT_mxcoff_build_id_EQ)) {
+    StringRef BuildId = A->getValue();
+    if (BuildId[0] != '0' || BuildId[1] != 'x' ||
+        BuildId.find_if_not(llvm::isHexDigit, 2) != StringRef::npos)
+      ToolChain.getDriver().Diag(diag::err_drv_unsupported_option_argument)
+          << A->getSpelling() << BuildId;
+    else {
+      std::string LinkerFlag = "-bdbg:ldrinfo:xcoff_binary_id:0x";
+      if (BuildId.size() % 2) // Prepend a 0 if odd number of digits.
+        LinkerFlag += "0";
+      LinkerFlag += BuildId.drop_front(2).lower();
+      CmdArgs.push_back(Args.MakeArgString(LinkerFlag));
+    }
+  }
+
   // Specify linker output file.
   assert((Output.isFilename() || Output.isNothing()) && "Invalid output.");
   if (Output.isFilename()) {
     CmdArgs.push_back("-o");
     CmdArgs.push_back(Output.getFilename());
   }
 
   // Set linking mode (i.e., 32/64-bit) and the address of

clang/test/Driver/xcoff-build-id.c

+// RUN: touch %t.o
+// RUN: %clang --target=powerpc64-ibm-aix -### %t.o -mxcoff-build-id=0x12 2>&1 | FileCheck %s
+// Test that:
+//  1) our ldrinfo flag comes before any user specified ldrinfo flag;
+//  2) upper case hex digits are converted to lower case;
+//  3) a zero is added when odd number of digits is specified in the HEXSTRING.
+// RUN: %clang --target=powerpc-ibm-aix -### %t.o -Wl,-bdbg:ldrinfo:FOO -mxcoff-build-id=0x011ffFF 2>&1 | FileCheck %s --check-prefix=OTHER
+
+// RUN: %clang --target=powerpc-ibm-aix -### %t.o -mxcoff-build-id=ff 2>&1 | FileCheck %s --check-prefix=BAD_INPUT
+// RUN: %clang --target=powerpc-ibm-aix -### %t.o -mxcoff-build-id=0x0z  2>&1 | FileCheck %s --check-prefix=BAD_INPUT
+
+CHECK: "-bdbg:ldrinfo:xcoff_binary_id:0x12"
+OTHER: "-bdbg:ldrinfo:xcoff_binary_id:0x0011ffff" {{.*}} "-bdbg:ldrinfo:FOO"
+BAD_INPUT: clang: error: unsupported argument {{.*}} to option '-mxcoff-build-id='