[GVN] Preserve loop related analysis/canonical forms.

LoopInfo can be easily preserved by passing it to the functions that
modify the CFG (SplitCriticalEdge and MergeBlockIntoPredecessor.
SplitCriticalEdge also preserves LoopSimplify and LCSSA form when when passing in
LoopInfo. The test case shows that we preserve LoopSimplify and
LoopInfo. Adding addPreservedID(LCSSAID) did not preserve LCSSA for some
reason.

Also I am not sure if it is possible to preserve those in the new pass
manager, as they aren't analysis passes.

Reviewers: reames, hfinkel, davide, jdoerfert

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D65137

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@367332 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/CFG.h b/include/llvm/Analysis/CFG.h
index bb55e76ac86a73b6f9370f5a099c8e5e94f8ab92..68f137ba622ca855ce778a31ac64a7b298eaaf35 100644 (file)
--- a/include/llvm/Analysis/CFG.h
+++ b/include/llvm/Analysis/CFG.h
@@ -46,6 +46,8 @@ unsigned GetSuccessorNumber(const BasicBlock *BB, const BasicBlock *Succ);
 ///
 bool isCriticalEdge(const Instruction *TI, unsigned SuccNum,
                     bool AllowIdenticalEdges = false);
+bool isCriticalEdge(const Instruction *TI, const BasicBlock *Succ,
+                    bool AllowIdenticalEdges = false);
 
 /// Determine whether instruction 'To' is reachable from 'From', without passing
 /// through any blocks in ExclusionSet, returning true if uncertain.

diff --git a/include/llvm/Transforms/Scalar/GVN.h b/include/llvm/Transforms/Scalar/GVN.h
index 9fe00a9e7f2d79e434cf6698ce7ad004ecd5dcac..2c9287f86cdccbac5f50a9c0b7f101234803f796 100644 (file)
--- a/include/llvm/Transforms/Scalar/GVN.h
+++ b/include/llvm/Transforms/Scalar/GVN.h
@@ -159,6 +159,7 @@ private:
   SetVector<BasicBlock *> DeadBlocks;
   OptimizationRemarkEmitter *ORE;
   ImplicitControlFlowTracking *ICF;
+  LoopInfo *LI;
 
   ValueTable VN;
 

diff --git a/lib/Analysis/CFG.cpp b/lib/Analysis/CFG.cpp
index 18b83d6838cc94d985115a828432d52e59c28947..8215b4ecbb03dc316c5789d3f8e0aaa49a105f4f 100644 (file)
--- a/lib/Analysis/CFG.cpp
+++ b/lib/Analysis/CFG.cpp
@@ -87,11 +87,18 @@ unsigned llvm::GetSuccessorNumber(const BasicBlock *BB,
 /// with multiple predecessors.
 bool llvm::isCriticalEdge(const Instruction *TI, unsigned SuccNum,
                           bool AllowIdenticalEdges) {
-  assert(TI->isTerminator() && "Must be a terminator to have successors!");
   assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!");
+  return isCriticalEdge(TI, TI->getSuccessor(SuccNum), AllowIdenticalEdges);
+}
+
+bool llvm::isCriticalEdge(const Instruction *TI, const BasicBlock *Dest,
+                          bool AllowIdenticalEdges) {
+  assert(TI->isTerminator() && "Must be a terminator to have successors!");
   if (TI->getNumSuccessors() == 1) return false;
 
-  const BasicBlock *Dest = TI->getSuccessor(SuccNum);
+  assert(find(predecessors(Dest), TI->getParent()) != pred_end(Dest) &&
+         "No edge between TI's block and Dest.");
+
   const_pred_iterator I = pred_begin(Dest), E = pred_end(Dest);
 
   // If there is more than one predecessor, this is a critical edge...

diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index 1a02e9d33f49f29d0f4ad3d85e6aa22a469763c8..29911a4ed2877ad25f9a686536ca0fff48f1aa80 100644 (file)
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -70,6 +70,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/SSAUpdater.h"
@@ -626,6 +627,8 @@ PreservedAnalyses GVN::run(Function &F, FunctionAnalysisManager &AM) {
   PA.preserve<DominatorTreeAnalysis>();
   PA.preserve<GlobalsAA>();
   PA.preserve<TargetLibraryAnalysis>();
+  if (LI)
+    PA.preserve<LoopAnalysis>();
   return PA;
 }
 
@@ -1976,6 +1979,7 @@ bool GVN::runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
   MD = RunMD;
   ImplicitControlFlowTracking ImplicitCFT(DT);
   ICF = &ImplicitCFT;
+  this->LI = LI;
   VN.setMemDep(MD);
   ORE = RunORE;
   InvalidBlockRPONumbers = true;
@@ -2335,7 +2339,7 @@ bool GVN::performPRE(Function &F) {
 /// the block inserted to the critical edge.
 BasicBlock *GVN::splitCriticalEdges(BasicBlock *Pred, BasicBlock *Succ) {
   BasicBlock *BB =
-      SplitCriticalEdge(Pred, Succ, CriticalEdgeSplittingOptions(DT));
+      SplitCriticalEdge(Pred, Succ, CriticalEdgeSplittingOptions(DT, LI));
   if (MD)
     MD->invalidateCachedPredecessors();
   InvalidBlockRPONumbers = true;
@@ -2350,7 +2354,7 @@ bool GVN::splitCriticalEdges() {
   do {
     std::pair<Instruction *, unsigned> Edge = toSplit.pop_back_val();
     SplitCriticalEdge(Edge.first, Edge.second,
-                      CriticalEdgeSplittingOptions(DT));
+                      CriticalEdgeSplittingOptions(DT, LI));
   } while (!toSplit.empty());
   if (MD) MD->invalidateCachedPredecessors();
   InvalidBlockRPONumbers = true;
@@ -2456,18 +2460,26 @@ void GVN::addDeadBlock(BasicBlock *BB) {
     if (DeadBlocks.count(B))
       continue;
 
+    // First, split the critical edges. This might also create additional blocks
+    // to preserve LoopSimplify form and adjust edges accordingly.
     SmallVector<BasicBlock *, 4> Preds(pred_begin(B), pred_end(B));
     for (BasicBlock *P : Preds) {
       if (!DeadBlocks.count(P))
         continue;
 
-      if (isCriticalEdge(P->getTerminator(), GetSuccessorNumber(P, B))) {
+      if (llvm::any_of(successors(P),
+                       [B](BasicBlock *Succ) { return Succ == B; }) &&
+          isCriticalEdge(P->getTerminator(), B)) {
         if (BasicBlock *S = splitCriticalEdges(P, B))
           DeadBlocks.insert(P = S);
       }
+    }
 
-      for (BasicBlock::iterator II = B->begin(); isa<PHINode>(II); ++II) {
-        PHINode &Phi = cast<PHINode>(*II);
+    // Now undef the incoming values from the dead predecessors.
+    for (BasicBlock *P : predecessors(B)) {
+      if (!DeadBlocks.count(P))
+        continue;
+      for (PHINode &Phi : B->phis()) {
         Phi.setIncomingValueForBlock(P, UndefValue::get(Phi.getType()));
         if (MD)
           MD->invalidateCachedPointerInfo(&Phi);
@@ -2556,6 +2568,7 @@ public:
     AU.addRequired<AssumptionCacheTracker>();
     AU.addRequired<DominatorTreeWrapperPass>();
     AU.addRequired<TargetLibraryInfoWrapperPass>();
+    AU.addRequired<LoopInfoWrapperPass>();
     if (!NoMemDepAnalysis)
       AU.addRequired<MemoryDependenceWrapperPass>();
     AU.addRequired<AAResultsWrapperPass>();
@@ -2563,6 +2576,8 @@ public:
     AU.addPreserved<DominatorTreeWrapperPass>();
     AU.addPreserved<GlobalsAAWrapperPass>();
     AU.addPreserved<TargetLibraryInfoWrapperPass>();
+    AU.addPreserved<LoopInfoWrapperPass>();
+    AU.addPreservedID(LoopSimplifyID);
     AU.addRequired<OptimizationRemarkEmitterWrapperPass>();
   }
 

diff --git a/test/Transforms/GVN/PRE/2011-06-01-NonLocalMemdepMiscompile.ll b/test/Transforms/GVN/PRE/2011-06-01-NonLocalMemdepMiscompile.ll
index 05dc79db95adecb948263bbc4fe62590d49b1525..6592c69b027fc431142d188ef3d4444fd43ed8e7 100644 (file)
--- a/test/Transforms/GVN/PRE/2011-06-01-NonLocalMemdepMiscompile.ll
+++ b/test/Transforms/GVN/PRE/2011-06-01-NonLocalMemdepMiscompile.ll
@@ -50,8 +50,14 @@ bb15:
   %tmp18 = icmp eq i8 %tmp17, 0
   br label %bb19
 
-; CHECK: bb15:
-; CHECK: %tmp17 = phi i8 [ %tmp17.pre, %bb1.bb15_crit_edge ], [ %tmp8, %bb6 ]
+; CHECK-LABEL: bb6:
+; CHECK:         br i1 undef, label %bb15split, label %bb10
+
+; CHECK-LABEL: bb15split:                                        ; preds = %bb6
+; CHECK-NEXT:    br label %bb15
+
+; CHECK-LABEL: bb15:
+; CHECK:         %tmp17 = phi i8 [ %tmp8, %bb15split ], [ %tmp17.pre, %bb1.bb15_crit_edge ]
 
 bb19:                                             ; preds = %bb15
   ret i1 %tmp18

diff --git a/test/Transforms/GVN/preserve-analysis.ll b/test/Transforms/GVN/preserve-analysis.ll
new file mode 100644 (file)
index 0000000..2454bb1
--- /dev/null
+++ b/test/Transforms/GVN/preserve-analysis.ll
@@ -0,0 +1,56 @@
+; RUN: opt < %s -debug-pass=Structure -indvars -gvn -indvars 2>&1 -S | FileCheck --check-prefix=CHECK --check-prefix=IR %s
+; RUN: opt < %s -debug-pass-manager -passes='require<domtree>,loop(simplify-cfg),gvn,loop(indvars)' 2>&1 -S | FileCheck --check-prefix=NEW-PM --check-prefix=IR %s
+
+; Check CFG-only analysis are preserved by SCCP by running it between 2
+; loop-vectorize runs.
+
+; CHECK: Dominator Tree Construction
+; CHECK: Natural Loop Information
+; CHECK: Canonicalize natural loops
+; CHECK: LCSSA Verifier
+; CHECK: Loop-Closed SSA Form Pass
+; CHECK: Global Value Numbering
+; CHECK-NOT: Dominator Tree Construction
+; CHECK-NOT: Natural Loop Information
+; CHECK-NOT: Canonicalize natural loops
+
+; NEW-PM-DAG: Running analysis: LoopAnalysis on test
+; NEW-PM-DAG: Running analysis: DominatorTreeAnalysis on test
+; NEW-PM: Running pass: GVN on test
+; NEW-PM-NOT: Running analysis: LoopAnalysis on test
+; NEW-PM-NOT: Running analysis: DominatorTreeAnalysis on test
+
+declare i1 @cond()
+declare void @dostuff()
+
+define i32 @test() {
+; IR-LABEL: define i32 @test()
+; IR-LABEL: header:
+; IR:         br i1 false, label %then, label %latch
+; IR-LABEL: then:
+; IR-NEXT:   call void @dostuff()
+; IR-NEXT:   br label %latch
+entry:
+  %res = add i32 1, 10
+  br label %header
+
+header:
+  %iv = phi i32 [ %res, %entry ], [ 0, %latch ]
+  %ic = icmp eq i32 %res, 99
+  br i1 %ic, label %then, label %latch
+
+then:
+  br label %then.2
+
+then.2:
+  call void @dostuff()
+  br label %latch
+
+
+latch:
+  %ec = call i1 @cond()
+  br i1 %ec, label %exit, label %header
+
+exit:
+  ret i32 %iv
+}