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

1 files changed, 18 insertions, 0 deletions

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;
 }