[PATCH] Attach attribute "trap-func-name" to IR function

[Akira Hatanaka]

Hi echristo, dexonsmith,

This patch is part of the work to make LTO and function multi-versioning work 
correctly.

Currently, the trap function name users specify on the command line using 
-ftrap-function is passed to the backend via TargetMachine's TargetOptions. 
This patch attaches attribute "trap-func-name" to the IR function instead so 
that we can use -ftrap-function for LTO builds and change the trap function 
name on a per-function basis.

http://reviews.llvm.org/D10831

Files:
  include/clang/Driver/CC1Options.td
  include/clang/Frontend/CodeGenOptions.h
  lib/CodeGen/BackendUtil.cpp
  lib/CodeGen/CGCall.cpp
  lib/Driver/Tools.cpp
  lib/Frontend/CompilerInvocation.cpp
  test/CodeGen/fn-attr.c

EMAIL PREFERENCES
  http://reviews.llvm.org/settings/panel/emailpreferences/

Index: include/clang/Driver/CC1Options.td
===================================================================
--- include/clang/Driver/CC1Options.td
+++ include/clang/Driver/CC1Options.td
@@ -223,6 +223,8 @@
   HelpText<"Do not put zero initialized data in the BSS">;
 def backend_option : Separate<["-"], "backend-option">,
   HelpText<"Additional arguments to forward to LLVM backend (during code gen)">;
+def function_attribute : Separate<["-"], "function-attribute">,
+  HelpText<"Function attributes to attach to functions (during code gen)">;
 def mregparm : Separate<["-"], "mregparm">,
   HelpText<"Limit the number of registers available for integer arguments">;
 def mrelocation_model : Separate<["-"], "mrelocation-model">,
Index: include/clang/Frontend/CodeGenOptions.h
===================================================================
--- include/clang/Frontend/CodeGenOptions.h
+++ include/clang/Frontend/CodeGenOptions.h
@@ -151,6 +151,10 @@
   /// A list of command-line options to forward to the LLVM backend.
   std::vector<std::string> BackendOptions;
 
+  /// A list of function attributes in the form of key-value pairs to save to
+  /// the IR.
+  std::vector<std::pair<std::string, std::string>> FunctionAttributes;
+
   /// A list of dependent libraries.
   std::vector<std::string> DependentLibraries;
 
Index: lib/CodeGen/BackendUtil.cpp
===================================================================
--- lib/CodeGen/BackendUtil.cpp
+++ lib/CodeGen/BackendUtil.cpp
@@ -536,7 +536,6 @@
   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
-  Options.TrapFuncName = CodeGenOpts.TrapFuncName;
   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;
   Options.FunctionSections = CodeGenOpts.FunctionSections;
   Options.DataSections = CodeGenOpts.DataSections;
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -1455,6 +1455,9 @@
       FuncAttrs.addAttribute(llvm::Attribute::NoBuiltin);
   } else {
     // Attributes that should go on the function, but not the call site.
+    for (auto &KV : CodeGenOpts.FunctionAttributes)
+      FuncAttrs.addAttribute(KV.first, KV.second);
+
     if (!CodeGenOpts.DisableFPElim) {
       FuncAttrs.addAttribute("no-frame-pointer-elim", "false");
     } else if (CodeGenOpts.OmitLeafFramePointer) {
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -3938,7 +3938,11 @@
     CmdArgs.push_back(A->getValue());
   }
 
-  Args.AddLastArg(CmdArgs, options::OPT_ftrap_function_EQ);
+  if (Arg *A = Args.getLastArg(options::OPT_ftrap_function_EQ)) {
+    CmdArgs.push_back("-function-attribute");
+    auto AttrStr = Twine("trap-func-name=") + A->getValue();
+    CmdArgs.push_back(Args.MakeArgString(AttrStr));
+  }
 
   // -fno-strict-overflow implies -fwrapv if it isn't disabled, but
   // -fstrict-overflow won't turn off an explicitly enabled -fwrapv.
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -356,6 +356,14 @@
   }
 }
 
+static void getFunctionAttributes(CodeGenOptions &Opts,
+                                  const std::vector<std::string> &FnAttrStrs) {
+  for (const auto &S : FnAttrStrs) {
+    std::pair<StringRef, StringRef> KV = StringRef(S).split('=');
+    Opts.FunctionAttributes.push_back(std::make_pair(KV.first, KV.second));
+  }
+}
+
 static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
                              DiagnosticsEngine &Diags,
                              const TargetOptions &TargetOpts) {
@@ -496,7 +504,6 @@
     Diags.Report(diag::err_drv_invalid_value)
         << Args.getLastArg(OPT_mthread_model)->getAsString(Args)
         << Opts.ThreadModel;
-  Opts.TrapFuncName = Args.getLastArgValue(OPT_ftrap_function_EQ);
   Opts.UseInitArray = Args.hasArg(OPT_fuse_init_array);
 
   Opts.FunctionSections = Args.hasFlag(OPT_ffunction_sections,
@@ -668,6 +675,7 @@
                       Args.getAllArgValues(OPT_fsanitize_trap_EQ), Diags,
                       Opts.SanitizeTrap);
 
+  getFunctionAttributes(Opts, Args.getAllArgValues(OPT_function_attribute));
   Opts.CudaGpuBinaryFileNames =
       Args.getAllArgValues(OPT_fcuda_include_gpubinary);
 
Index: test/CodeGen/fn-attr.c
===================================================================
--- /dev/null
+++ test/CodeGen/fn-attr.c
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -triple thumbv7-apple-ios5 -function-attribute trap-func-name=trapfuncname1 -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: attributes #0 = { {{.*}} "trap-func-name"="trapfuncname1"
+
+int foo1(int a) { return a; }

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