[Attributor] Manifest constant return values
Summary:
If the unique return value is a constant we now replace call uses with
that constant.
Reviewers: sstefan1, uenoku
Subscribers: hiraditya, bollu, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66551
llvm-svn: 369785
diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index 9367f48..f75fc2c 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -807,10 +807,34 @@
STATS_DECLTRACK(UniqueReturnValue, FunctionReturn,
"Number of function with unique return");
+ // Callback to replace the uses of CB with the constant C.
+ auto ReplaceCallSiteUsersWith = [](CallBase &CB, Constant &C) {
+ if (CB.getNumUses() == 0)
+ return ChangeStatus::UNCHANGED;
+ CB.replaceAllUsesWith(&C);
+ return ChangeStatus::CHANGED;
+ };
+
// If the assumed unique return value is an argument, annotate it.
if (auto *UniqueRVArg = dyn_cast<Argument>(UniqueRV.getValue())) {
getIRPosition() = IRPosition::argument(*UniqueRVArg);
- Changed = IRAttribute::manifest(A) | Changed;
+ Changed = IRAttribute::manifest(A);
+ } else if (auto *RVC = dyn_cast<Constant>(UniqueRV.getValue())) {
+ // We can replace the returned value with the unique returned constant.
+ Value &AnchorValue = getAnchorValue();
+ if (Function *F = dyn_cast<Function>(&AnchorValue)) {
+ for (const Use &U : F->uses())
+ if (CallBase *CB = dyn_cast<CallBase>(U.getUser()))
+ if (CB->isCallee(&U))
+ Changed = ReplaceCallSiteUsersWith(*CB, *RVC) | Changed;
+ } else {
+ assert(isa<CallBase>(AnchorValue) &&
+ "Expcected a function or call base anchor!");
+ Changed = ReplaceCallSiteUsersWith(cast<CallBase>(AnchorValue), *RVC);
+ }
+ if (Changed == ChangeStatus::CHANGED)
+ STATS_DECLTRACK(UniqueConstantReturnValue, FunctionReturn,
+ "Number of function returns replaced by constant return");
}
return Changed;