[MachineOutliner] Add support for target-default outlining.

This adds functionality to the outliner that allows targets to
specify certain functions that should be outlined from by default.

If a target supports default outlining, then it specifies that in
its TargetOptions. In the case that it does, and the user hasn't
specified that they *never* want to outline, the outliner will
be added to the pass pipeline and will run on those default functions.

This is a preliminary patch for turning the outliner on by default
under -Oz for AArch64.

https://reviews.llvm.org/D48776

llvm-svn: 336040

1 files changed, 9 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
index dfdf676..3fca2f4 100644
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -111,11 +111,11 @@ static cl::opt<bool> VerifyMachineCode("verify-machineinstrs", cl::Hidden,
     cl::desc("Verify generated machine code"),
     cl::init(false),
     cl::ZeroOrMore);
-enum RunOutliner { AlwaysOutline, NeverOutline };
+enum RunOutliner { AlwaysOutline, NeverOutline, TargetDefault };
 // Enable or disable the MachineOutliner.
 static cl::opt<RunOutliner> EnableMachineOutliner(
     "enable-machine-outliner", cl::desc("Enable the machine outliner"),
-    cl::Hidden, cl::ValueOptional, cl::init(NeverOutline),
+    cl::Hidden, cl::ValueOptional, cl::init(TargetDefault),
     cl::values(clEnumValN(AlwaysOutline, "always",
                           "Run on all functions guaranteed to be beneficial"),
                clEnumValN(NeverOutline, "never", "Disable all outlining"),
@@ -914,8 +914,13 @@ void TargetPassConfig::addMachinePasses() {
   addPass(&PatchableFunctionID, false);
 
   if (TM->Options.EnableMachineOutliner && getOptLevel() != CodeGenOpt::None &&
-      EnableMachineOutliner == AlwaysOutline)
-    addPass(createMachineOutlinerPass());
+      EnableMachineOutliner != NeverOutline) {
+    bool RunOnAllFunctions = (EnableMachineOutliner == AlwaysOutline);
+    bool AddOutliner = RunOnAllFunctions ||
+                       TM->Options.SupportsDefaultOutlining;
+    if (AddOutliner)
+      addPass(createMachineOutlinerPass(RunOnAllFunctions));
+  }
 
   // Add passes that directly emit MI after all other MI passes.
   addPreEmitPass2();