instcombine: Migrate memmove optimizations

This patch migrates the memmove optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167687 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index c57991bd9e..b4dc93dead 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -978,6 +978,25 @@ struct MemCpyOpt : public LibCallOptimization {
   }
 };
 
+struct MemMoveOpt : public LibCallOptimization {
+  virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    // These optimizations require DataLayout.
+    if (!TD) return 0;
+
+    FunctionType *FT = Callee->getFunctionType();
+    if (FT->getNumParams() != 3 || FT->getReturnType() != FT->getParamType(0) ||
+        !FT->getParamType(0)->isPointerTy() ||
+        !FT->getParamType(1)->isPointerTy() ||
+        FT->getParamType(2) != TD->getIntPtrType(*Context))
+      return 0;
+
+    // memmove(x, y, n) -> llvm.memmove(x, y, n, 1)
+    B.CreateMemMove(CI->getArgOperand(0), CI->getArgOperand(1),
+                    CI->getArgOperand(2), 1);
+    return CI->getArgOperand(0);
+  }
+};
+
 } // End anonymous namespace.
 
 namespace llvm {
@@ -1016,6 +1035,7 @@ class LibCallSimplifierImpl {
   // Memory library call optimizations.
   MemCmpOpt MemCmp;
   MemCpyOpt MemCpy;
+  MemMoveOpt MemMove;
 
   void initOptimizations();
   void addOpt(LibFunc::Func F, LibCallOptimization* Opt);
@@ -1066,6 +1086,7 @@ void LibCallSimplifierImpl::initOptimizations() {
   // Memory library call optimizations.
   addOpt(LibFunc::memcmp, &MemCmp);
   addOpt(LibFunc::memcpy, &MemCpy);
+  addOpt(LibFunc::memmove, &MemMove);
 }
 
 Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {