Make more passes preserve dominators (or state that they preserve dominators if

they all ready do). This removes two dominator recomputations prior to isel,
which is a 1% improvement in total llc time for 403.gcc.

The only potentially suspect thing is making GCStrategy recompute dominators if
it used a custom lowering strategy.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123064 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 49 insertions, 2 deletions

diff --git a/lib/CodeGen/GCStrategy.cpp b/lib/CodeGen/GCStrategy.cpp
index 824cac84d5..d8c3742afd 100644
--- a/lib/CodeGen/GCStrategy.cpp
+++ b/lib/CodeGen/GCStrategy.cpp
@@ -19,6 +19,7 @@
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/IntrinsicInst.h"
 #include "llvm/Module.h"
+#include "llvm/Analysis/Dominators.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -146,6 +147,7 @@ const char *LowerIntrinsics::getPassName() const {
 void LowerIntrinsics::getAnalysisUsage(AnalysisUsage &AU) const {
   FunctionPass::getAnalysisUsage(AU);
   AU.addRequired<GCModuleInfo>();
+  AU.addPreserved<DominatorTree>();
 }
 
 /// doInitialization - If this module uses the GC intrinsics, find them now.
@@ -256,9 +258,16 @@ bool LowerIntrinsics::runOnFunction(Function &F) {
   if (NeedsDefaultLoweringPass(S))
     MadeChange |= PerformDefaultLowering(F, S);
   
-  if (NeedsCustomLoweringPass(S))
+  bool UseCustomLoweringPass = NeedsCustomLoweringPass(S);
+  if (UseCustomLoweringPass)
     MadeChange |= S.performCustomLowering(F);
-  
+
+  // Custom lowering may modify the CFG, so dominators must be recomputed.
+  if (UseCustomLoweringPass) {
+    if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>())
+      DT->DT->recalculate(F);
+  }
+
   return MadeChange;
 }
 
diff --git a/lib/CodeGen/StackProtector.cpp b/lib/CodeGen/StackProtector.cpp
index 61dd7b1bc1..fcaee4208b 100644
--- a/lib/CodeGen/StackProtector.cpp
+++ b/lib/CodeGen/StackProtector.cpp
@@ -16,6 +16,7 @@
 
 #define DEBUG_TYPE "stack-protector"
 #include "llvm/CodeGen/Passes.h"
+#include "llvm/Analysis/Dominators.h"
 #include "llvm/Attributes.h"
 #include "llvm/Constants.h"
 #include "llvm/DerivedTypes.h"
@@ -45,6 +46,8 @@ namespace {
     Function *F;
     Module *M;
 
+    DominatorTree* DT;
+
     /// InsertStackProtectors - Insert code into the prologue and epilogue of
     /// the function.
     ///
@@ -70,6 +73,10 @@ namespace {
         initializeStackProtectorPass(*PassRegistry::getPassRegistry());
       }
 
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addPreserved<DominatorTree>();
+    }
+
     virtual bool runOnFunction(Function &Fn);
   };
 } // end anonymous namespace
@@ -85,6 +92,7 @@ FunctionPass *llvm::createStackProtectorPass(const TargetLowering *tli) {
 bool StackProtector::runOnFunction(Function &Fn) {
   F = &Fn;
   M = F->getParent();
+  DT = getAnalysisIfAvailable<DominatorTree>();
 
   if (!RequiresStackProtector()) return false;
   
@@ -139,6 +147,7 @@ bool StackProtector::RequiresStackProtector() const {
 ///    value. It calls __stack_chk_fail if they differ.
 bool StackProtector::InsertStackProtectors() {
   BasicBlock *FailBB = 0;       // The basic block to jump to if check fails.
+  BasicBlock *FailBBDom = 0;    // FailBB's dominator.
   AllocaInst *AI = 0;           // Place on stack that stores the stack guard.
   Value *StackGuardVar = 0;  // The stack guard variable.
 
@@ -182,6 +191,8 @@ bool StackProtector::InsertStackProtectors() {
 
       // Create the basic block to jump to when the guard check fails.
       FailBB = CreateFailBB();
+      if (DT)
+        FailBBDom = DT->isReachableFromEntry(BB) ? BB : 0;
     }
 
     // For each block with a return instruction, convert this:
@@ -208,6 +219,10 @@ bool StackProtector::InsertStackProtectors() {
 
     // Split the basic block before the return instruction.
     BasicBlock *NewBB = BB->splitBasicBlock(RI, "SP_return");
+    if (DT) {
+      DT->addNewBlock(NewBB, DT->isReachableFromEntry(BB) ? BB : 0);
+      FailBBDom = DT->findNearestCommonDominator(FailBBDom, BB);
+    }
 
     // Remove default branch instruction to the new BB.
     BB->getTerminator()->eraseFromParent();
@@ -227,6 +242,9 @@ bool StackProtector::InsertStackProtectors() {
   // statements in the function.
   if (!FailBB) return false;
 
+  if (DT)
+    DT->addNewBlock(FailBB, FailBBDom);
+
   return true;
 }
 
diff --git a/lib/CodeGen/UnreachableBlockElim.cpp b/lib/CodeGen/UnreachableBlockElim.cpp
index 4fdb228824..48d8ab1658 100644
--- a/lib/CodeGen/UnreachableBlockElim.cpp
+++ b/lib/CodeGen/UnreachableBlockElim.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Function.h"
 #include "llvm/Pass.h"
 #include "llvm/Type.h"
+#include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/ProfileInfo.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
@@ -48,6 +49,7 @@ namespace {
     }
 
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addPreserved<DominatorTree>();
       AU.addPreserved<ProfileInfo>();
     }
   };
diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index e3e634339e..1068108f07 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -22,6 +22,7 @@
 #include "llvm/Instructions.h"
 #include "llvm/IntrinsicInst.h"
 #include "llvm/Pass.h"
+#include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/ProfileInfo.h"
 #include "llvm/Target/TargetData.h"
@@ -66,6 +67,7 @@ namespace {
     /// TLI - Keep a pointer of a TargetLowering to consult for determining
     /// transformation profitability.
     const TargetLowering *TLI;
+    DominatorTree *DT;
     ProfileInfo *PFI;
 
     /// BackEdges - Keep a set of all the loop back edges.
@@ -86,6 +88,7 @@ namespace {
     bool runOnFunction(Function &F);
 
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addPreserved<DominatorTree>();
       AU.addPreserved<ProfileInfo>();
     }
 
@@ -131,6 +134,7 @@ void CodeGenPrepare::findLoopBackEdges(const Function &F) {
 bool CodeGenPrepare::runOnFunction(Function &F) {
   bool EverMadeChange = false;
 
+  DT = getAnalysisIfAvailable<DominatorTree>();
   PFI = getAnalysisIfAvailable<ProfileInfo>();
   // First pass, eliminate blocks that contain only PHI nodes and an
   // unconditional branch.
@@ -325,6 +329,13 @@ void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
   // The PHIs are now updated, change everything that refers to BB to use
   // DestBB and remove BB.
   BB->replaceAllUsesWith(DestBB);
+  if (DT) {
+    BasicBlock *BBIDom  = DT->getNode(BB)->getIDom()->getBlock();
+    BasicBlock *DestBBIDom = DT->getNode(DestBB)->getIDom()->getBlock();
+    BasicBlock *NewIDom = DT->findNearestCommonDominator(BBIDom, DestBBIDom);
+    DT->changeImmediateDominator(DestBB, NewIDom);
+    DT->eraseNode(BB);
+  }
   if (PFI) {
     PFI->replaceAllUses(BB, DestBB);
     PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB));
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index 4c2bdbc226..30e88e976f 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -22,6 +22,7 @@
 #include "llvm/IntrinsicInst.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/ProfileInfo.h"
@@ -401,6 +402,12 @@ void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, Pass *P) {
   PredBB->replaceAllUsesWith(DestBB);
   
   if (P) {
+    DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>();
+    if (DT) {
+      BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
+      DT->changeImmediateDominator(DestBB, PredBBIDom);
+      DT->eraseNode(PredBB);
+    }
     ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>();
     if (PI) {
       PI->replaceAllUses(PredBB, DestBB);