IRMover: Steal arguments when moving functions, NFC
Instead of copying arguments from the source function to the
destination, steal them. This has a few advantages.
- The ValueMap doesn't need to be seeded with (or cleared of)
Arguments.
- Often the destination function won't have created any arguments yet,
so this avoids malloc traffic.
- Argument names don't need to be copied.
Because argument lists are lazy, this required a new
Function::stealArgumentListFrom helper.
llvm-svn: 265519
diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index 7826971..115419a 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -302,6 +302,28 @@
const_cast<Function*>(this)->setValueSubclassData(SDC &= ~(1<<0));
}
+void Function::stealArgumentListFrom(Function &Src) {
+ assert(isDeclaration() && "Expected no references to current arguments");
+
+ // Drop the current arguments, if any, and set the lazy argument bit.
+ if (!hasLazyArguments()) {
+ assert(llvm::all_of(ArgumentList,
+ [](const Argument &A) { return A.use_empty(); }) &&
+ "Expected arguments to be unused in declaration");
+ ArgumentList.clear();
+ setValueSubclassData(getSubclassDataFromValue() | (1 << 0));
+ }
+
+ // Nothing to steal if Src has lazy arguments.
+ if (Src.hasLazyArguments())
+ return;
+
+ // Steal arguments from Src, and fix the lazy argument bits.
+ ArgumentList.splice(ArgumentList.end(), Src.ArgumentList);
+ setValueSubclassData(getSubclassDataFromValue() & ~(1 << 0));
+ Src.setValueSubclassData(Src.getSubclassDataFromValue() | (1 << 0));
+}
+
size_t Function::arg_size() const {
return getFunctionType()->getNumParams();
}