[SelectOpti] Auto-disable other cmov optis when the new select-opti pass is enabled

[davidxl]

llvm/lib/CodeGen/CodeGenPrepare.cpp

6719

select optimization also depends on other conditions such as PGO etc for now. Should we check if it is actually enabled?

[apostolakis]

llvm/lib/CodeGen/CodeGenPrepare.cpp

6719

The optimization is indeed much more effective with PGO since most of its heuristics rely on profile information. Yet, there is still some benefit for non-PGO builds, especially for AArch64. In fact, we have seen significant improvements (up to 3x speedups) for non-PGO builds for some ARM microbenchmarks. Some heuristics are only enabled for PGO builds while other ones such as the loop-level analysis improve their cost modeling with profile information but are still operational with conservative assumptions for weights for non-PGO builds. Therefore, I would avoid excluding any build (including non-PGO ones) from enabling the optimization.

[davidxl]

lgtm

llvm/lib/CodeGen/CodeGenPrepare.cpp

 }
 
 /// If we have a SelectInst that will likely profit from branch prediction,
 /// turn it into a branch.
 bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
   if (DisableSelectToBranch)
     return false;
 
+  // If the SelectOptimize pass is enabled, selects have already been optimized.
+  if (!getCGPassBuilderOption().DisableSelectOptimize)
+    return false;
+
   // Find all consecutive select instructions that share the same condition.
   SmallVector<SelectInst *, 2> ASI;
   ASI.push_back(SI);
   for (BasicBlock::iterator It = ++BasicBlock::iterator(SI);
        It != SI->getParent()->end(); ++It) {
     SelectInst *I = dyn_cast<SelectInst>(&*It);
     if (I && SI->getCondition() == I->getCondition()) {
       ASI.push_back(I);

llvm/lib/Target/X86/X86CmovConversion.cpp

 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/MC/MCSchedule.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/CGPassBuilderOption.h"
 #include <algorithm>
 #include <cassert>
 #include <iterator>
 #include <utility>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "x86-cmov-conversion"

 }
 
 bool X86CmovConverterPass::runOnMachineFunction(MachineFunction &MF) {
   if (skipFunction(MF.getFunction()))
     return false;
   if (!EnableCmovConverter)
     return false;
 
+  // If the SelectOptimize pass is enabled, cmovs have already been optimized.
+  if (!getCGPassBuilderOption().DisableSelectOptimize)
+    return false;
+
   LLVM_DEBUG(dbgs() << "********** " << getPassName() << " : " << MF.getName()
                     << "**********\n");
 
   bool Changed = false;
   MLI = &getAnalysis<MachineLoopInfo>();
   const TargetSubtargetInfo &STI = MF.getSubtarget();
   MRI = &MF.getRegInfo();
   TII = STI.getInstrInfo();