[InstCombine] Improve TryToSinkInstruction with multiple uses

This patch allows sinking an instruction which can have multiple uses in a
single user. We were previously over-restrictive by looking for exactly one use,
rather than one user.

Also, the API for retrieving undroppable user has been updated accordingly since
in both usecases (Attributor and InstCombine), we seem to care about the user,
rather than the use.

Reviewed-By: nikic

Differential Revision: https://reviews.llvm.org/D109700

1 files changed, 6 insertions, 6 deletions

diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index da67da1..a47ab68 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -164,13 +164,13 @@ bool Value::hasOneUser() const {
 
 static bool isUnDroppableUser(const User *U) { return !U->isDroppable(); }
 
-Use *Value::getSingleUndroppableUse() {
-  Use *Result = nullptr;
-  for (Use &U : uses()) {
-    if (!U.getUser()->isDroppable()) {
-      if (Result)
+User *Value::getUniqueUndroppableUser() {
+  User *Result = nullptr;
+  for (auto *U : users()) {
+    if (!U->isDroppable()) {
+      if (Result && Result != U)
         return nullptr;
-      Result = &U;
+      Result = U;
     }
   }
   return Result;