1 files changed, 21 insertions, 0 deletions
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index b4dc93dead..c3ea63852f 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -997,6 +997,25 @@ struct MemMoveOpt : public LibCallOptimization {
   }
 };
 
+struct MemSetOpt : 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)->isIntegerTy() ||
+        FT->getParamType(2) != TD->getIntPtrType(*Context))
+      return 0;
+
+    // memset(p, v, n) -> llvm.memset(p, v, n, 1)
+    Value *Val = B.CreateIntCast(CI->getArgOperand(1), B.getInt8Ty(), false);
+    B.CreateMemSet(CI->getArgOperand(0), Val, CI->getArgOperand(2), 1);
+    return CI->getArgOperand(0);
+  }
+};
+
 } // End anonymous namespace.
 
 namespace llvm {
@@ -1036,6 +1055,7 @@ class LibCallSimplifierImpl {
   MemCmpOpt MemCmp;
   MemCpyOpt MemCpy;
   MemMoveOpt MemMove;
+  MemSetOpt MemSet;
 
   void initOptimizations();
   void addOpt(LibFunc::Func F, LibCallOptimization* Opt);
@@ -1087,6 +1107,7 @@ void LibCallSimplifierImpl::initOptimizations() {
   addOpt(LibFunc::memcmp, &MemCmp);
   addOpt(LibFunc::memcpy, &MemCpy);
   addOpt(LibFunc::memmove, &MemMove);
+  addOpt(LibFunc::memset, &MemSet);
 }
 
 Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {