From a303c417bbdb53703c2c17398b08486bde78f1f6 Mon Sep 17 00:00:00 2001
From: Dimitry Andric <dim@FreeBSD.org>
Date: Tue, 2 May 2017 18:30:13 +0000
Subject: Vendor import of llvm trunk r301939:
 https://llvm.org/svn/llvm-project/llvm/trunk@301939

---
 lib/Transforms/Scalar/JumpThreading.cpp | 62 +++++++++++++++++++++++----------
 1 file changed, 43 insertions(+), 19 deletions(-)

(limited to 'lib/Transforms/Scalar/JumpThreading.cpp')

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index a0da81605a809..7dacaba1193e8 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -557,7 +557,7 @@ bool JumpThreadingPass::ComputeValueKnownInPredecessors(
         Value *LHS = PN->getIncomingValue(i);
         Value *RHS = Cmp->getOperand(1)->DoPHITranslation(BB, PredBB);
 
-        Value *Res = SimplifyCmpInst(Cmp->getPredicate(), LHS, RHS, DL);
+        Value *Res = SimplifyCmpInst(Cmp->getPredicate(), LHS, RHS, {DL});
         if (!Res) {
           if (!isa<Constant>(RHS))
             continue;
@@ -1250,37 +1250,53 @@ bool JumpThreadingPass::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
 
   BasicBlock *OnlyDest = nullptr;
   BasicBlock *MultipleDestSentinel = (BasicBlock*)(intptr_t)~0ULL;
+  Constant *OnlyVal = nullptr;
+  Constant *MultipleVal = (Constant *)(intptr_t)~0ULL;
 
+  unsigned PredWithKnownDest = 0;
   for (const auto &PredValue : PredValues) {
     BasicBlock *Pred = PredValue.second;
     if (!SeenPreds.insert(Pred).second)
       continue;  // Duplicate predecessor entry.
 
-    // If the predecessor ends with an indirect goto, we can't change its
-    // destination.
-    if (isa<IndirectBrInst>(Pred->getTerminator()))
-      continue;
-
     Constant *Val = PredValue.first;
 
     BasicBlock *DestBB;
     if (isa<UndefValue>(Val))
       DestBB = nullptr;
-    else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()))
+    else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
+      assert(isa<ConstantInt>(Val) && "Expecting a constant integer");
       DestBB = BI->getSuccessor(cast<ConstantInt>(Val)->isZero());
-    else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
+    } else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
+      assert(isa<ConstantInt>(Val) && "Expecting a constant integer");
       DestBB = SI->findCaseValue(cast<ConstantInt>(Val))->getCaseSuccessor();
     } else {
       assert(isa<IndirectBrInst>(BB->getTerminator())
               && "Unexpected terminator");
+      assert(isa<BlockAddress>(Val) && "Expecting a constant blockaddress");
       DestBB = cast<BlockAddress>(Val)->getBasicBlock();
     }
 
     // If we have exactly one destination, remember it for efficiency below.
-    if (PredToDestList.empty())
+    if (PredToDestList.empty()) {
       OnlyDest = DestBB;
-    else if (OnlyDest != DestBB)
-      OnlyDest = MultipleDestSentinel;
+      OnlyVal = Val;
+    } else {
+      if (OnlyDest != DestBB)
+        OnlyDest = MultipleDestSentinel;
+      // It possible we have same destination, but different value, e.g. default
+      // case in switchinst.
+      if (Val != OnlyVal)
+        OnlyVal = MultipleVal;
+    }
+
+    // We know where this predecessor is going.
+    ++PredWithKnownDest;
+
+    // If the predecessor ends with an indirect goto, we can't change its
+    // destination.
+    if (isa<IndirectBrInst>(Pred->getTerminator()))
+      continue;
 
     PredToDestList.push_back(std::make_pair(Pred, DestBB));
   }
@@ -1293,7 +1309,7 @@ bool JumpThreadingPass::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
   // not thread. By doing so, we do not need to duplicate the current block and
   // also miss potential opportunities in case we dont/cant duplicate.
   if (OnlyDest && OnlyDest != MultipleDestSentinel) {
-    if (PredToDestList.size() ==
+    if (PredWithKnownDest ==
         (size_t)std::distance(pred_begin(BB), pred_end(BB))) {
       bool SeenFirstBranchToOnlyDest = false;
       for (BasicBlock *SuccBB : successors(BB)) {
@@ -1310,11 +1326,18 @@ bool JumpThreadingPass::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
 
       // If the condition is now dead due to the removal of the old terminator,
       // erase it.
-      auto *CondInst = dyn_cast<Instruction>(Cond);
-      if (CondInst && CondInst->use_empty())
-        CondInst->eraseFromParent();
-      // FIXME: in case this instruction is defined in the current BB and it
-      // resolves to a single value from all predecessors, we can do RAUW.
+      if (auto *CondInst = dyn_cast<Instruction>(Cond)) {
+        if (CondInst->use_empty() && !CondInst->mayHaveSideEffects())
+          CondInst->eraseFromParent();
+        else if (OnlyVal && OnlyVal != MultipleVal &&
+                 CondInst->getParent() == BB) {
+          // If we just learned Cond is the same value for all uses of the
+          // condition, replace it with a constant value
+          CondInst->replaceAllUsesWith(OnlyVal);
+          if (!CondInst->mayHaveSideEffects())
+            CondInst->eraseFromParent();
+        }
+      }
       return true;
     }
   }
@@ -1883,8 +1906,9 @@ bool JumpThreadingPass::DuplicateCondBranchOnPHIIntoPred(
     // If this instruction can be simplified after the operands are updated,
     // just use the simplified value instead.  This frequently happens due to
     // phi translation.
-    if (Value *IV =
-            SimplifyInstruction(New, BB->getModule()->getDataLayout())) {
+    if (Value *IV = SimplifyInstruction(
+            New,
+            {BB->getModule()->getDataLayout(), TLI, nullptr, nullptr, New})) {
       ValueMapping[&*BI] = IV;
       if (!New->mayHaveSideEffects()) {
         delete New;
-- 
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