Misc mid-level changes for new 'fence' instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136205 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 18 insertions, 5 deletions

diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp
index e6089a9a43..a645f92116 100644
--- a/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -665,7 +665,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
       
       continue;
     }
-    
+
     AliasAnalysis::Location LoadedLoc;
     
     // If we encounter a use of the pointer, it is no longer considered dead
@@ -675,9 +675,12 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
       LoadedLoc = AA->getLocation(V);
     } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(BBI)) {
       LoadedLoc = AA->getLocationForSource(MTI);
-    } else {
-      // Not a loading instruction.
+    } else if (!BBI->mayReadOrWriteMemory()) {
+      // Instruction doesn't touch memory.
       continue;
+    } else {
+      // Unknown inst; assume it clobbers everything.
+      break;
     }
 
     // Remove any allocas from the DeadPointer set that are loaded, as this
diff --git a/lib/Transforms/Scalar/LowerAtomic.cpp b/lib/Transforms/Scalar/LowerAtomic.cpp
index 9087b46c13..7f4d9e9c43 100644
--- a/lib/Transforms/Scalar/LowerAtomic.cpp
+++ b/lib/Transforms/Scalar/LowerAtomic.cpp
@@ -115,6 +115,11 @@ static bool LowerAtomicIntrinsic(IntrinsicInst *II) {
   return true;
 }
 
+static bool LowerFenceInst(FenceInst *FI) {
+  FI->eraseFromParent();
+  return true;
+}
+
 namespace {
   struct LowerAtomic : public BasicBlockPass {
     static char ID;
@@ -123,9 +128,13 @@ namespace {
     }
     bool runOnBasicBlock(BasicBlock &BB) {
       bool Changed = false;
-      for (BasicBlock::iterator DI = BB.begin(), DE = BB.end(); DI != DE; )
-        if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(DI++))
+      for (BasicBlock::iterator DI = BB.begin(), DE = BB.end(); DI != DE; ) {
+        Instruction *Inst = DI++;
+        if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
           Changed |= LowerAtomicIntrinsic(II);
+        if (FenceInst *FI = dyn_cast<FenceInst>(Inst))
+          Changed |= LowerFenceInst(FI);
+      }
       return Changed;
     }
   };
diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 67570e60bb..749ba40a64 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -530,6 +530,7 @@ private:
   void visitCallSite      (CallSite CS);
   void visitUnwindInst    (TerminatorInst &I) { /*returns void*/ }
   void visitUnreachableInst(TerminatorInst &I) { /*returns void*/ }
+  void visitFenceInst     (FenceInst &I) { /*returns void*/ }
   void visitAllocaInst    (Instruction &I) { markOverdefined(&I); }
   void visitVAArgInst     (Instruction &I) { markAnythingOverdefined(&I); }