From: Igor Laevsky <igmyrj@gmail.com>
Date: Wed, 8 Feb 2017 14:23:47 +0000 (+0000)
Subject: [InstCombineCalls] Remove zero length atomic memcpy intrinsics
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=25ddfba83378042c2ea1254f254cb7bf40d82b48;p=llvm

[InstCombineCalls] Remove zero length atomic memcpy intrinsics

Differential Revision: https://reviews.llvm.org/D28909



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294452 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/IR/IntrinsicInst.h b/include/llvm/IR/IntrinsicInst.h
index 7f4eb0e9df8..f69b5bfc0be 100644
--- a/include/llvm/IR/IntrinsicInst.h
+++ b/include/llvm/IR/IntrinsicInst.h
@@ -191,6 +191,32 @@ namespace llvm {
     }
   };
 
+  /// This class represents atomic memcpy intrinsic
+  /// TODO: Integrate this class into MemIntrinsic hierarchy.
+  class ElementAtomicMemCpyInst : public IntrinsicInst {
+  public:
+    Value *getRawDest() const { return getArgOperand(0); }
+    Value *getRawSource() const { return getArgOperand(1); }
+
+    Value *getNumElements() const { return getArgOperand(2); }
+    void setNumElements(Value *V) { setArgOperand(2, V); }
+
+    uint64_t getSrcAlignment() const { return getParamAlignment(1); }
+    uint64_t getDstAlignment() const { return getParamAlignment(2); }
+
+    uint64_t getElementSizeInBytes() const {
+      Value *Arg = getArgOperand(3);
+      return cast<ConstantInt>(Arg)->getZExtValue();
+    }
+
+    static inline bool classof(const IntrinsicInst *I) {
+      return I->getIntrinsicID() == Intrinsic::memcpy_element_atomic;
+    }
+    static inline bool classof(const Value *V) {
+      return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
+    }
+  };
+
   /// This is the common base class for memset/memcpy/memmove.
   class MemIntrinsic : public IntrinsicInst {
   public:
diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index f088671c6d7..13f2f9e9c72 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1835,6 +1835,12 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
     if (Changed) return II;
   }
 
+  if (auto *AMI = dyn_cast<ElementAtomicMemCpyInst>(II)) {
+    if (Constant *C = dyn_cast<Constant>(AMI->getNumElements()))
+      if (C->isNullValue())
+        return eraseInstFromFunction(*AMI);
+  }
+
   if (Instruction *I = SimplifyNVVMIntrinsic(II, *this))
     return I;