1 files changed, 35 insertions, 14 deletions

diff --git a/lib/Transforms/Scalar/EarlyCSE.cpp b/lib/Transforms/Scalar/EarlyCSE.cpp
index 04479b6e49ac8..d8f8a58a5fdfa 100644
--- a/lib/Transforms/Scalar/EarlyCSE.cpp
+++ b/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -253,6 +253,7 @@ public:
   const TargetTransformInfo &TTI;
   DominatorTree &DT;
   AssumptionCache ∾
+  const SimplifyQuery SQ;
   MemorySSA *MSSA;
   std::unique_ptr<MemorySSAUpdater> MSSAUpdater;
   typedef RecyclingAllocator<
@@ -315,9 +316,10 @@ public:
   unsigned CurrentGeneration;
 
   /// \brief Set up the EarlyCSE runner for a particular function.
-  EarlyCSE(const TargetLibraryInfo &TLI, const TargetTransformInfo &TTI,
-           DominatorTree &DT, AssumptionCache &AC, MemorySSA *MSSA)
-      : TLI(TLI), TTI(TTI), DT(DT), AC(AC), MSSA(MSSA),
+  EarlyCSE(const DataLayout &DL, const TargetLibraryInfo &TLI,
+           const TargetTransformInfo &TTI, DominatorTree &DT,
+           AssumptionCache &AC, MemorySSA *MSSA)
+      : TLI(TLI), TTI(TTI), DT(DT), AC(AC), SQ(DL, &TLI, &DT, &AC), MSSA(MSSA),
         MSSAUpdater(make_unique<MemorySSAUpdater>(MSSA)), CurrentGeneration(0) {
   }
 
@@ -616,8 +618,6 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
   /// stores which can occur in bitfield code among other things.
   Instruction *LastStore = nullptr;
 
-  const DataLayout &DL = BB->getModule()->getDataLayout();
-
   // See if any instructions in the block can be eliminated.  If so, do it.  If
   // not, add them to AvailableValues.
   for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
@@ -635,10 +635,16 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
 
     // Skip assume intrinsics, they don't really have side effects (although
     // they're marked as such to ensure preservation of control dependencies),
-    // and this pass will not disturb any of the assumption's control
-    // dependencies.
+    // and this pass will not bother with its removal. However, we should mark
+    // its condition as true for all dominated blocks.
     if (match(Inst, m_Intrinsic<Intrinsic::assume>())) {
-      DEBUG(dbgs() << "EarlyCSE skipping assumption: " << *Inst << '\n');
+      auto *CondI =
+          dyn_cast<Instruction>(cast<CallInst>(Inst)->getArgOperand(0));
+      if (CondI && SimpleValue::canHandle(CondI)) {
+        DEBUG(dbgs() << "EarlyCSE considering assumption: " << *Inst << '\n');
+        AvailableValues.insert(CondI, ConstantInt::getTrue(BB->getContext()));
+      } else
+        DEBUG(dbgs() << "EarlyCSE skipping assumption: " << *Inst << '\n');
       continue;
     }
 
@@ -658,10 +664,25 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
     if (match(Inst, m_Intrinsic<Intrinsic::experimental_guard>())) {
       if (auto *CondI =
               dyn_cast<Instruction>(cast<CallInst>(Inst)->getArgOperand(0))) {
-        // The condition we're on guarding here is true for all dominated
-        // locations.
-        if (SimpleValue::canHandle(CondI))
+        if (SimpleValue::canHandle(CondI)) {
+          // Do we already know the actual value of this condition?
+          if (auto *KnownCond = AvailableValues.lookup(CondI)) {
+            // Is the condition known to be true?
+            if (isa<ConstantInt>(KnownCond) &&
+                cast<ConstantInt>(KnownCond)->isOneValue()) {
+              DEBUG(dbgs() << "EarlyCSE removing guard: " << *Inst << '\n');
+              removeMSSA(Inst);
+              Inst->eraseFromParent();
+              Changed = true;
+              continue;
+            } else
+              // Use the known value if it wasn't true.
+              cast<CallInst>(Inst)->setArgOperand(0, KnownCond);
+          }
+          // The condition we're on guarding here is true for all dominated
+          // locations.
           AvailableValues.insert(CondI, ConstantInt::getTrue(BB->getContext()));
+        }
       }
 
       // Guard intrinsics read all memory, but don't write any memory.
@@ -673,7 +694,7 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
 
     // If the instruction can be simplified (e.g. X+0 = X) then replace it with
     // its simpler value.
-    if (Value *V = SimplifyInstruction(Inst, DL, &TLI, &DT, &AC)) {
+    if (Value *V = SimplifyInstruction(Inst, SQ)) {
       DEBUG(dbgs() << "EarlyCSE Simplify: " << *Inst << "  to: " << *V << '\n');
       bool Killed = false;
       if (!Inst->use_empty()) {
@@ -964,7 +985,7 @@ PreservedAnalyses EarlyCSEPass::run(Function &F,
   auto *MSSA =
       UseMemorySSA ? &AM.getResult<MemorySSAAnalysis>(F).getMSSA() : nullptr;
 
-  EarlyCSE CSE(TLI, TTI, DT, AC, MSSA);
+  EarlyCSE CSE(F.getParent()->getDataLayout(), TLI, TTI, DT, AC, MSSA);
 
   if (!CSE.run())
     return PreservedAnalyses::all();
@@ -1008,7 +1029,7 @@ public:
     auto *MSSA =
         UseMemorySSA ? &getAnalysis<MemorySSAWrapperPass>().getMSSA() : nullptr;
 
-    EarlyCSE CSE(TLI, TTI, DT, AC, MSSA);
+    EarlyCSE CSE(F.getParent()->getDataLayout(), TLI, TTI, DT, AC, MSSA);
 
     return CSE.run();
   }