Provide a place for targets to insert ILP optimization passes.

Move the early if-conversion pass into this group.

ILP optimizations usually need to find the right balance between
register pressure and ILP using the MachineTraceMetrics analysis to
identify critical paths and estimate other costs. Such passes should run
together so they can share dominator tree and loop info analyses.

Besides if-conversion, future passes to run here here could include
expression height reduction and ARM's MLxExpansion pass.

llvm-svn: 172687

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/Passes.cpp b/llvm/lib/CodeGen/Passes.cpp
index 2a135bcc1e1..02a14914f11 100644
--- a/llvm/lib/CodeGen/Passes.cpp
+++ b/llvm/lib/CodeGen/Passes.cpp
@@ -238,9 +238,6 @@ TargetPassConfig::TargetPassConfig(TargetMachine *tm, PassManagerBase &pm)
   substitutePass(&EarlyTailDuplicateID, &TailDuplicateID);
   substitutePass(&PostRAMachineLICMID, &MachineLICMID);
 
-  // Disable early if-conversion. Targets that are ready can enable it.
-  disablePass(&EarlyIfConverterID);
-
   // Temporarily disable experimental passes.
   const TargetSubtargetInfo &ST = TM->getSubtarget<TargetSubtargetInfo>();
   if (!ST.enableMachineScheduler())
@@ -551,7 +548,12 @@ void TargetPassConfig::addMachineSSAOptimization() {
   addPass(&DeadMachineInstructionElimID);
   printAndVerify("After codegen DCE pass");
 
-  addPass(&EarlyIfConverterID);
+  // Allow targets to insert passes that improve instruction level parallelism,
+  // like if-conversion. Such passes will typically need dominator trees and
+  // loop info, just like LICM and CSE below.
+  if (addILPOpts())
+    printAndVerify("After ILP optimizations");
+
   addPass(&MachineLICMID);
   addPass(&MachineCSEID);
   addPass(&MachineSinkingID);