Revert r80926. It causes loop unswitch assertion and slow down some JIT tests significantly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81101 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index 736d26e..c165e04 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -24,7 +24,6 @@
#include "llvm/Analysis/Dominators.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Transforms/Scalar.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ValueHandle.h"
#include <algorithm>
@@ -320,8 +319,7 @@
++SplitIt;
BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
- // The new block lives in whichever loop the old one did. This preserves
- // LCSSA as well, because we force the split point to be after any PHI nodes.
+ // The new block lives in whichever loop the old one did.
if (LoopInfo* LI = P->getAnalysisIfAvailable<LoopInfo>())
if (Loop *L = LI->getLoopFor(Old))
L->addBasicBlockToLoop(New, LI->getBase());
@@ -355,12 +353,8 @@
/// Preds array, which has NumPreds elements in it. The new block is given a
/// suffix of 'Suffix'.
///
-/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
-/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
-/// In particular, it does not preserve LoopSimplify (because it's
-/// complicated to handle the case where one of the edges being split
-/// is an exit of a loop with other exits).
-///
+/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and
+/// DominanceFrontier, but no other analyses.
BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
BasicBlock *const *Preds,
unsigned NumPreds, const char *Suffix,
@@ -372,44 +366,19 @@
// The new block unconditionally branches to the old block.
BranchInst *BI = BranchInst::Create(BB, NewBB);
- LoopInfo *LI = P ? P->getAnalysisIfAvailable<LoopInfo>() : 0;
- Loop *L = LI ? LI->getLoopFor(BB) : 0;
- bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID);
-
// Move the edges from Preds to point to NewBB instead of BB.
- // While here, if we need to preserve loop analyses, collect
- // some information about how this split will affect loops.
- bool HasLoopExit = false;
- bool IsLoopEntry = !!L;
- bool SplitMakesNewLoopHeader = false;
- for (unsigned i = 0; i != NumPreds; ++i) {
+ for (unsigned i = 0; i != NumPreds; ++i)
Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
-
- if (LI) {
- // If we need to preserve LCSSA, determine if any of
- // the preds is a loop exit.
- if (PreserveLCSSA)
- if (Loop *PL = LI->getLoopFor(Preds[i]))
- if (!PL->contains(BB))
- HasLoopExit = true;
- // If we need to preserve LoopInfo, note whether any of the
- // preds crosses an interesting loop boundary.
- if (L) {
- if (L->contains(Preds[i]))
- IsLoopEntry = false;
- else
- SplitMakesNewLoopHeader = true;
- }
- }
- }
-
+
// Update dominator tree and dominator frontier if available.
DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
if (DT)
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable<DominanceFrontier>():0)
DF->splitBlock(NewBB);
-
+ AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
+
+
// Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
// node becomes an incoming value for BB's phi node. However, if the Preds
// list is empty, we need to insert dummy entries into the PHI nodes in BB to
@@ -420,42 +389,20 @@
cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
return NewBB;
}
-
- AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
-
- if (L) {
- if (IsLoopEntry) {
- if (Loop *PredLoop = LI->getLoopFor(Preds[0])) {
- // Add the new block to the nearest enclosing loop (and not an
- // adjacent loop).
- while (PredLoop && !PredLoop->contains(BB))
- PredLoop = PredLoop->getParentLoop();
- if (PredLoop)
- PredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
- }
- } else {
- L->addBasicBlockToLoop(NewBB, LI->getBase());
- if (SplitMakesNewLoopHeader)
- L->moveToHeader(NewBB);
- }
- }
// Otherwise, create a new PHI node in NewBB for each PHI node in BB.
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
PHINode *PN = cast<PHINode>(I++);
// Check to see if all of the values coming in are the same. If so, we
- // don't need to create a new PHI node, unless it's needed for LCSSA.
- Value *InVal = 0;
- if (!HasLoopExit) {
- InVal = PN->getIncomingValueForBlock(Preds[0]);
- for (unsigned i = 1; i != NumPreds; ++i)
- if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
- InVal = 0;
- break;
- }
- }
-
+ // don't need to create a new PHI node.
+ Value *InVal = PN->getIncomingValueForBlock(Preds[0]);
+ for (unsigned i = 1; i != NumPreds; ++i)
+ if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
+ InVal = 0;
+ break;
+ }
+
if (InVal) {
// If all incoming values for the new PHI would be the same, just don't
// make a new PHI. Instead, just remove the incoming values from the old
@@ -480,6 +427,13 @@
// Add an incoming value to the PHI node in the loop for the preheader
// edge.
PN->addIncoming(InVal, NewBB);
+
+ // Check to see if we can eliminate this phi node.
+ if (Value *V = PN->hasConstantValue(DT)) {
+ PN->replaceAllUsesWith(V);
+ if (AA) AA->deleteValue(PN);
+ PN->eraseFromParent();
+ }
}
return NewBB;