Emit memmove, not memcpy, for structure copies; this is unfortunately
required for correctness in cases of copying a struct to itself or to
an overlapping struct (itself for cases like *a = *a, and overlapping
is possible with unions).
Hopefully, this won't end up being a perf issue; LLVM *should* be able
to optimize memmove to memcpy in a lot of cases, and for small copies
the generated code *should* be mostly comparable. (In reality, LLVM
is currently horrible at optimizing memmove, but that's a bug, not a
fundamental issue.)
gcc currently generates wrong code; that's
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32667.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@51566 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index ec61d66..329599c 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -35,7 +35,8 @@
llvm::Module &M, const llvm::TargetData &TD,
Diagnostic &diags, bool GenerateDebugInfo)
: Context(C), Features(LO), TheModule(M), TheTargetData(TD), Diags(diags),
- Types(C, M, TD), MemCpyFn(0), MemSetFn(0), CFConstantStringClassRef(0) {
+ Types(C, M, TD), MemCpyFn(0), MemMoveFn(0), MemSetFn(0),
+ CFConstantStringClassRef(0) {
//TODO: Make this selectable at runtime
Runtime = CreateObjCRuntime(M,
getTypes().ConvertType(getContext().IntTy),
@@ -589,6 +590,17 @@
return MemCpyFn = getIntrinsic(IID);
}
+llvm::Function *CodeGenModule::getMemMoveFn() {
+ if (MemMoveFn) return MemMoveFn;
+ llvm::Intrinsic::ID IID;
+ switch (Context.Target.getPointerWidth(0)) {
+ default: assert(0 && "Unknown ptr width");
+ case 32: IID = llvm::Intrinsic::memmove_i32; break;
+ case 64: IID = llvm::Intrinsic::memmove_i64; break;
+ }
+ return MemMoveFn = getIntrinsic(IID);
+}
+
llvm::Function *CodeGenModule::getMemSetFn() {
if (MemSetFn) return MemSetFn;
llvm::Intrinsic::ID IID;