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
diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index e3e6343..1068108 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 @@
/// 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 @@
bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addPreserved<DominatorTree>();
AU.addPreserved<ProfileInfo>();
}
@@ -131,6 +134,7 @@
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 @@
// 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));