[MachineOutliner] Add always and never options to -enable-machine-outliner

To enable the MachineOutliner by default on AArch64, we need to be able to
disable the MachineOutliner and also provide an option to "always" enable the
outliner.

This adds that capability. It allows the user to still use the old
-enable-machine-outliner option, which defaults to "always". This is building
up to allowing the user to specify "always" versus the target-default
outlining behaviour.

llvm-svn: 335872

2 files changed, 42 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
index 8c5bdde888e..20771eef620 100644
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -111,9 +111,17 @@ static cl::opt<bool> VerifyMachineCode("verify-machineinstrs", cl::Hidden,
     cl::desc("Verify generated machine code"),
     cl::init(false),
     cl::ZeroOrMore);
-static cl::opt<bool> EnableMachineOutliner("enable-machine-outliner",
-    cl::Hidden,
-    cl::desc("Enable machine outliner"));
+enum RunOutliner { AlwaysOutline, NeverOutline };
+// 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::values(clEnumValN(AlwaysOutline, "always",
+                          "Run on all functions guaranteed to be beneficial "
+                          "(pass -enable-linkonceodr-outlining for more)"),
+               clEnumValN(NeverOutline, "never", "Disable all outlining"),
+               // Sentinel value for unspecified option.
+               clEnumValN(AlwaysOutline, "", "")));
 // Enable or disable FastISel. Both options are needed, because
 // FastISel is enabled by default with -fast, and we wish to be
 // able to enable or disable fast-isel independently from -O0.
@@ -906,7 +914,7 @@ void TargetPassConfig::addMachinePasses() {
   addPass(&XRayInstrumentationID, false);
   addPass(&PatchableFunctionID, false);
 
-  if (EnableMachineOutliner)
+  if (EnableMachineOutliner == AlwaysOutline)
     addPass(createMachineOutlinerPass());
 
   // Add passes that directly emit MI after all other MI passes.
diff --git a/llvm/test/CodeGen/AArch64/machine-outliner-flags.ll b/llvm/test/CodeGen/AArch64/machine-outliner-flags.ll
new file mode 100644
index 00000000000..0f232c8a1f0
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/machine-outliner-flags.ll
@@ -0,0 +1,30 @@
+; RUN: llc %s -debug-pass=Structure -verify-machineinstrs \
+; RUN: -enable-machine-outliner=always -mtriple arm64---- -o /dev/null 2>&1 \
+; RUN: | FileCheck %s -check-prefix=ALWAYS
+
+; RUN: llc %s -debug-pass=Structure -verify-machineinstrs \
+; RUN: -enable-machine-outliner -mtriple arm64---- -o /dev/null 2>&1 \
+; RUN: | FileCheck %s -check-prefix=ENABLE
+
+; RUN: llc %s -debug-pass=Structure -verify-machineinstrs \
+; RUN: -enable-machine-outliner=never -mtriple arm64---- -o /dev/null 2>&1 \
+; RUN: | FileCheck %s -check-prefix=NEVER
+
+; RUN: llc %s -debug-pass=Structure -verify-machineinstrs \
+; RUN: -mtriple arm64---- -o /dev/null 2>&1 \
+; RUN: | FileCheck %s -check-prefix=NOT-ADDED
+
+; Make sure that the outliner flags all work properly. If we specify
+; -enable-machine-outliner with always or no argument, it should be added to the
+; pass pipeline. If we specify it with never, or don't pass the flag,
+; then we shouldn't add it.
+
+; ALWAYS: Machine Outliner
+; ENABLE: Machine Outliner
+; NEVER-NOT: Machine Outliner
+; NOT-ADDED-NOT: Machine Outliner
+
+define void @foo() {
+  ret void;
+}
+