[Driver] Pass -O* to the gold plugin via -plugin-opt

[jmolloy]

Summary

The gold plugin understands -O0..-O3, but these are not currently being passed to it.

[• rafael]

This introduces a meaning to -ON during the link. That normally show up by people passing CFLAGS when linking.

I think that is OK, but would like a second opinion.

lib/Driver/Tools.cpp

1815

Can you refactor these 3 calls to push_back?

1817

Why do you need to manually issue a diagnostic?

[jmolloy]

Hi Rafael,

Thanks for the review!

This introduces a meaning to -ON during the link. That normally show up by people passing CFLAGS when linking.

Yes. The rationale is that with -flto, the link is also part of the compile. I think it's more surprising that the compiler isn't called with the -O options than the reverse!

James

lib/Driver/Tools.cpp

1815

Sure!

1817

You're right - I don't. I'll remove this.

[jmolloy]

Hi,

As we got to the bottom of why this is actually needed, I committed this with the changes suggested by Rafael in r256146.

Cheers,

James

lib/Driver/Tools.cpp

static void AddGoldPlugin(const ToolChain &ToolChain, const ArgList &Args,
   // Try to pass driver level flags relevant to LTO code generation down to
   // the plugin.
 
   // Handle flags for selecting CPU variants.
   std::string CPU = getCPUName(Args, ToolChain.getTriple());
   if (!CPU.empty())
     CmdArgs.push_back(Args.MakeArgString(Twine("-plugin-opt=mcpu=") + CPU));
 
+  if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
+    if (A->getOption().matches(options::OPT_O4) ||
+        A->getOption().matches(options::OPT_Ofast)) {
+      CmdArgs.push_back("-plugin-opt=O3");
+    } else if (A->getOption().matches(options::OPT_O)) {
+      CmdArgs.push_back(
+          Args.MakeArgString(Twine("-plugin-opt=O") + A->getValue()));
+    } else if (A->getOption().matches(options::OPT_O0)) {
+      CmdArgs.push_back("-plugin-opt=O0");
+    } else {
+      ToolChain.getDriver().Diag(clang::diag::warn_drv_unused_argument)
+          << A->getAsString(Args);
+    }
+  }
+
   if (IsThinLTO)
     CmdArgs.push_back("-plugin-opt=thinlto");
 }
 
 /// This is a helper function for validating the optional refinement step
 /// parameter in reciprocal argument strings. Return false if there is an error
 /// parsing the refinement step. Otherwise, return true and set the Position
 /// of the refinement step in the input string.

test/Driver/gold-lto.c

 // RUN: touch %t.o
 //
 // RUN: %clang -target x86_64-unknown-linux -### %t.o -flto 2>&1 \
-// RUN:     -Wl,-plugin-opt=foo \
+// RUN:     -Wl,-plugin-opt=foo -O3 \
 // RUN:     | FileCheck %s --check-prefix=CHECK-X86-64-BASIC
 // CHECK-X86-64-BASIC: "-plugin" "{{.*}}/LLVMgold.so"
+// CHECK-X86-64-BASIC: "-plugin-opt=O3"
 // CHECK-X86-64-BASIC: "-plugin-opt=foo"
 //
 // RUN: %clang -target x86_64-unknown-linux -### %t.o -flto 2>&1 \
-// RUN:     -march=corei7 -Wl,-plugin-opt=foo \
+// RUN:     -march=corei7 -Wl,-plugin-opt=foo -Ofast \
 // RUN:     | FileCheck %s --check-prefix=CHECK-X86-64-COREI7
 // CHECK-X86-64-COREI7: "-plugin" "{{.*}}/LLVMgold.so"
 // CHECK-X86-64-COREI7: "-plugin-opt=mcpu=corei7"
+// CHECK-X86-64-COREI7: "-plugin-opt=O3"
 // CHECK-X86-64-COREI7: "-plugin-opt=foo"
 //
 // RUN: %clang -target arm-unknown-linux -### %t.o -flto 2>&1 \
-// RUN:     -march=armv7a -Wl,-plugin-opt=foo \
+// RUN:     -march=armv7a -Wl,-plugin-opt=foo -O0 \
 // RUN:     | FileCheck %s --check-prefix=CHECK-ARM-V7A
 // CHECK-ARM-V7A: "-plugin" "{{.*}}/LLVMgold.so"
 // CHECK-ARM-V7A: "-plugin-opt=mcpu=cortex-a8"
+// CHECK-ARM-V7A: "-plugin-opt=O0"
 // CHECK-ARM-V7A: "-plugin-opt=foo"
 //
 // RUN: %clang -target i686-linux-android -### %t.o -flto 2>&1 \
 // RUN:     | FileCheck %s --check-prefix=CHECK-X86-ANDROID
 // CHECK-X86-ANDROID: "-plugin" "{{.*}}/LLVMgold.so"