Vendor import of llvm release_30 branch r142614:vendor/llvm/llvm-r142614

http://llvm.org/svn/llvm-project/llvm/branches/release_30@142614

1 files changed, 40 insertions, 24 deletions

diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index 66add6ca01ee..b79bb1300fec 100644
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -151,6 +151,11 @@ namespace {
     ///
     bool isSafeToExecuteUnconditionally(Instruction &I);
 
+    /// isGuaranteedToExecute - Check that the instruction is guaranteed to
+    /// execute.
+    ///
+    bool isGuaranteedToExecute(Instruction &I);
+
     /// pointerInvalidatedByLoop - Return true if the body of this loop may
     /// store into the memory location pointed to by V.
     ///
@@ -357,8 +362,8 @@ void LICM::HoistRegion(DomTreeNode *N) {
 bool LICM::canSinkOrHoistInst(Instruction &I) {
   // Loads have extra constraints we have to verify before we can hoist them.
   if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
-    if (LI->isVolatile())
-      return false;        // Don't hoist volatile loads!
+    if (!LI->isUnordered())
+      return false;        // Don't hoist volatile/atomic loads!
 
     // Loads from constant memory are always safe to move, even if they end up
     // in the same alias set as something that ends up being modified.
@@ -461,7 +466,7 @@ void LICM::sink(Instruction &I) {
     } else {
       // Move the instruction to the start of the exit block, after any PHI
       // nodes in it.
-      I.moveBefore(ExitBlocks[0]->getFirstNonPHI());
+      I.moveBefore(ExitBlocks[0]->getFirstInsertionPt());
 
       // This instruction is no longer in the AST for the current loop, because
       // we just sunk it out of the loop.  If we just sunk it into an outer
@@ -504,7 +509,7 @@ void LICM::sink(Instruction &I) {
       continue;
 
     // Insert the code after the last PHI node.
-    BasicBlock::iterator InsertPt = ExitBlock->getFirstNonPHI();
+    BasicBlock::iterator InsertPt = ExitBlock->getFirstInsertionPt();
 
     // If this is the first exit block processed, just move the original
     // instruction, otherwise clone the original instruction and insert
@@ -577,6 +582,10 @@ bool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) {
   if (Inst.isSafeToSpeculativelyExecute())
     return true;
 
+  return isGuaranteedToExecute(Inst);
+}
+
+bool LICM::isGuaranteedToExecute(Instruction &Inst) {
   // Otherwise we have to check to make sure that the instruction dominates all
   // of the exit blocks.  If it doesn't, then there is a path out of the loop
   // which does not execute this instruction, so we can't hoist it.
@@ -635,7 +644,7 @@ namespace {
       for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) {
         BasicBlock *ExitBlock = LoopExitBlocks[i];
         Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
-        Instruction *InsertPos = ExitBlock->getFirstNonPHI();
+        Instruction *InsertPos = ExitBlock->getFirstInsertionPt();
         StoreInst *NewSI = new StoreInst(LiveInValue, SomePtr, InsertPos);
         NewSI->setAlignment(Alignment);
         NewSI->setDebugLoc(DL);
@@ -713,34 +722,41 @@ void LICM::PromoteAliasSet(AliasSet &AS) {
 
       // If there is an non-load/store instruction in the loop, we can't promote
       // it.
-      unsigned InstAlignment;
       if (LoadInst *load = dyn_cast<LoadInst>(Use)) {
-        assert(!cast<LoadInst>(Use)->isVolatile() && "AST broken");
-        InstAlignment = load->getAlignment();
+        assert(!load->isVolatile() && "AST broken");
+        if (!load->isSimple())
+          return;
       } else if (StoreInst *store = dyn_cast<StoreInst>(Use)) {
         // Stores *of* the pointer are not interesting, only stores *to* the
         // pointer.
         if (Use->getOperand(1) != ASIV)
           continue;
-        InstAlignment = store->getAlignment();
-        assert(!cast<StoreInst>(Use)->isVolatile() && "AST broken");
+        assert(!store->isVolatile() && "AST broken");
+        if (!store->isSimple())
+          return;
+
+        // Note that we only check GuaranteedToExecute inside the store case
+        // so that we do not introduce stores where they did not exist before
+        // (which would break the LLVM concurrency model).
+
+        // If the alignment of this instruction allows us to specify a more
+        // restrictive (and performant) alignment and if we are sure this
+        // instruction will be executed, update the alignment.
+        // Larger is better, with the exception of 0 being the best alignment.
+        unsigned InstAlignment = store->getAlignment();
+        if ((InstAlignment > Alignment || InstAlignment == 0)
+            && (Alignment != 0))
+          if (isGuaranteedToExecute(*Use)) {
+            GuaranteedToExecute = true;
+            Alignment = InstAlignment;
+          }
+
+        if (!GuaranteedToExecute)
+          GuaranteedToExecute = isGuaranteedToExecute(*Use);
+
       } else
         return; // Not a load or store.
 
-      // If the alignment of this instruction allows us to specify a more
-      // restrictive (and performant) alignment and if we are sure this
-      // instruction will be executed, update the alignment.
-      // Larger is better, with the exception of 0 being the best alignment.
-      if ((InstAlignment > Alignment || InstAlignment == 0)
-          && (Alignment != 0))
-        if (isSafeToExecuteUnconditionally(*Use)) {
-          GuaranteedToExecute = true;
-          Alignment = InstAlignment;
-        }
-
-      if (!GuaranteedToExecute)
-        GuaranteedToExecute = isSafeToExecuteUnconditionally(*Use);
-
       LoopUses.push_back(Use);
     }
   }