[InstCombine] Transform bcopy to memmove

bcopy is still widely used mainly for network apps. Sadly, LLVM has no optimizations for bcopy, but there are some for memmove. 
Since bcopy == memmove, it is profitable to transform bcopy to memmove and use current optimizations for memmove for free here.

llvm-svn: 373537

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 3af754a..1fb4f28 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -2792,6 +2792,12 @@ Value *LibCallSimplifier::optimizePuts(CallInst *CI, IRBuilder<> &B) {
   return nullptr;
 }
 
+Value *LibCallSimplifier::optimizeBCopy(CallInst *CI, IRBuilder<> &B) {
+  // bcopy(src, dst, n) -> llvm.memmove(dst, src, n)
+  return B.CreateMemMove(CI->getArgOperand(1), 1, CI->getArgOperand(0), 1,
+                         CI->getArgOperand(2));
+}
+
 bool LibCallSimplifier::hasFloatVersion(StringRef FuncName) {
   LibFunc Func;
   SmallString<20> FloatFuncName = FuncName;
@@ -2870,6 +2876,8 @@ Value *LibCallSimplifier::optimizeStringMemoryLibCall(CallInst *CI,
       return optimizeRealloc(CI, Builder);
     case LibFunc_wcslen:
       return optimizeWcslen(CI, Builder);
+    case LibFunc_bcopy:
+      return optimizeBCopy(CI, Builder);
     default:
       break;
     }