[llvm] f0f73ed - [JumpThreading] Factor out code to clone instructions (NFC)

[Kazu Hirata via llvm-commits]

Author: Kazu Hirata
Date: 2019-11-06T14:16:48-08:00
New Revision: f0f73ed8b004d213a3710b7b850e09c5bbd8e93d

URL: https://github.com/llvm/llvm-project/commit/f0f73ed8b004d213a3710b7b850e09c5bbd8e93d
DIFF: https://github.com/llvm/llvm-project/commit/f0f73ed8b004d213a3710b7b850e09c5bbd8e93d.diff

LOG: [JumpThreading] Factor out code to clone instructions (NFC)

Summary:
This patch factors out code to clone instructions -- partly for
readability and partly to facilitate an upcoming patch of my own.

Reviewers: wmi

Subscribers: hiraditya, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69861

Added: 
    

Modified: 
    llvm/include/llvm/Transforms/Scalar/JumpThreading.h
    llvm/lib/Transforms/Scalar/JumpThreading.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Transforms/Scalar/JumpThreading.h b/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
index 591247277d23..16a9d5c43252 100644
--- a/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
+++ b/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
@@ -112,6 +112,10 @@ class JumpThreadingPass : public PassInfoMixin<JumpThreadingPass> {
   bool MaybeMergeBasicBlockIntoOnlyPred(BasicBlock *BB);
   void UpdateSSA(BasicBlock *BB, BasicBlock *NewBB,
                  DenseMap<Instruction *, Value *> &ValueMapping);
+  DenseMap<Instruction *, Value *> CloneInstructions(BasicBlock::iterator BI,
+                                                     BasicBlock::iterator BE,
+                                                     BasicBlock *NewBB,
+                                                     BasicBlock *PredBB);
   bool ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs,
                   BasicBlock *SuccBB);
   bool DuplicateCondBranchOnPHIIntoPred(

diff  --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 8582d295aa89..347e2cb273c6 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1973,6 +1973,48 @@ void JumpThreadingPass::UpdateSSA(
   }
 }
 
+/// Clone instructions in range [BI, BE) to NewBB.  For PHI nodes, we only clone
+/// arguments that come from PredBB.  Return the map from the variables in the
+/// source basic block to the variables in the newly created basic block.
+DenseMap<Instruction *, Value *>
+JumpThreadingPass::CloneInstructions(BasicBlock::iterator BI,
+                                     BasicBlock::iterator BE, BasicBlock *NewBB,
+                                     BasicBlock *PredBB) {
+  // We are going to have to map operands from the source basic block to the new
+  // copy of the block 'NewBB'.  If there are PHI nodes in the source basic
+  // block, evaluate them to account for entry from PredBB.
+  DenseMap<Instruction *, Value *> ValueMapping;
+
+  // Clone the phi nodes of the source basic block into NewBB.  The resulting
+  // phi nodes are trivial since NewBB only has one predecessor, but SSAUpdater
+  // might need to rewrite the operand of the cloned phi.
+  for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI) {
+    PHINode *NewPN = PHINode::Create(PN->getType(), 1, PN->getName(), NewBB);
+    NewPN->addIncoming(PN->getIncomingValueForBlock(PredBB), PredBB);
+    ValueMapping[PN] = NewPN;
+  }
+
+  // Clone the non-phi instructions of the source basic block into NewBB,
+  // keeping track of the mapping and using it to remap operands in the cloned
+  // instructions.
+  for (; BI != BE; ++BI) {
+    Instruction *New = BI->clone();
+    New->setName(BI->getName());
+    NewBB->getInstList().push_back(New);
+    ValueMapping[&*BI] = New;
+
+    // Remap operands to patch up intra-block references.
+    for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
+      if (Instruction *Inst = dyn_cast<Instruction>(New->getOperand(i))) {
+        DenseMap<Instruction *, Value *>::iterator I = ValueMapping.find(Inst);
+        if (I != ValueMapping.end())
+          New->setOperand(i, I->second);
+      }
+  }
+
+  return ValueMapping;
+}
+
 /// ThreadEdge - We have decided that it is safe and profitable to factor the
 /// blocks in PredBBs to one predecessor, then thread an edge from it to SuccBB
 /// across BB.  Transform the IR to reflect this change.
@@ -2030,11 +2072,6 @@ bool JumpThreadingPass::ThreadEdge(BasicBlock *BB,
     LVI->enableDT();
   LVI->threadEdge(PredBB, BB, SuccBB);
 
-  // We are going to have to map operands from the original BB block to the new
-  // copy of the block 'NewBB'.  If there are PHI nodes in BB, evaluate them to
-  // account for entry from PredBB.
-  DenseMap<Instruction*, Value*> ValueMapping;
-
   BasicBlock *NewBB = BasicBlock::Create(BB->getContext(),
                                          BB->getName()+".thread",
                                          BB->getParent(), BB);
@@ -2047,32 +2084,9 @@ bool JumpThreadingPass::ThreadEdge(BasicBlock *BB,
     BFI->setBlockFreq(NewBB, NewBBFreq.getFrequency());
   }
 
-  BasicBlock::iterator BI = BB->begin();
-  // Clone the phi nodes of BB into NewBB. The resulting phi nodes are trivial,
-  // since NewBB only has one predecessor, but SSAUpdater might need to rewrite
-  // the operand of the cloned phi.
-  for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI) {
-    PHINode *NewPN = PHINode::Create(PN->getType(), 1, PN->getName(), NewBB);
-    NewPN->addIncoming(PN->getIncomingValueForBlock(PredBB), PredBB);
-    ValueMapping[PN] = NewPN;
-  }
-
-  // Clone the non-phi instructions of BB into NewBB, keeping track of the
-  // mapping and using it to remap operands in the cloned instructions.
-  for (; !BI->isTerminator(); ++BI) {
-    Instruction *New = BI->clone();
-    New->setName(BI->getName());
-    NewBB->getInstList().push_back(New);
-    ValueMapping[&*BI] = New;
-
-    // Remap operands to patch up intra-block references.
-    for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
-      if (Instruction *Inst = dyn_cast<Instruction>(New->getOperand(i))) {
-        DenseMap<Instruction*, Value*>::iterator I = ValueMapping.find(Inst);
-        if (I != ValueMapping.end())
-          New->setOperand(i, I->second);
-      }
-  }
+  // Copy all the instructions from BB to NewBB except the terminator.
+  DenseMap<Instruction *, Value *> ValueMapping =
+      CloneInstructions(BB->begin(), std::prev(BB->end()), NewBB, PredBB);
 
   // We didn't copy the terminator from BB over to NewBB, because there is now
   // an unconditional jump to SuccBB.  Insert the unconditional jump.