[InstCombine] Allow sinking from unique predecessor with multiple edges
Summary: We can allow sinking if the single user block has only one unique predecessor, regardless of the number of edges. Note that a switch statement with multiple cases can have the same destination.
Reviewers: mcrosier, majnemer, spatel, reames
Subscribers: reames, mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D23722
llvm-svn: 279448
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 6424e08..12c42ce 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2903,7 +2903,7 @@
// If the user is one of our immediate successors, and if that successor
// only has us as a predecessors (we'd have to split the critical edge
// otherwise), we can keep going.
- if (UserIsSuccessor && UserParent->getSinglePredecessor()) {
+ if (UserIsSuccessor && UserParent->getUniquePredecessor()) {
// Okay, the CFG is simple enough, try to sink this instruction.
if (TryToSinkInstruction(I, UserParent)) {
DEBUG(dbgs() << "IC: Sink: " << *I << '\n');
diff --git a/llvm/test/Transforms/InstCombine/sink_instruction.ll b/llvm/test/Transforms/InstCombine/sink_instruction.ll
index 1bbd6b7..4c057c6 100644
--- a/llvm/test/Transforms/InstCombine/sink_instruction.ll
+++ b/llvm/test/Transforms/InstCombine/sink_instruction.ll
@@ -54,3 +54,26 @@
}
declare i32 @bar()
+
+define i32 @test3(i32* nocapture readonly %P, i32 %i) {
+entry:
+ %idxprom = sext i32 %i to i64
+ %arrayidx = getelementptr inbounds i32, i32* %P, i64 %idxprom
+ %0 = load i32, i32* %arrayidx, align 4
+ switch i32 %i, label %sw.epilog [
+ i32 5, label %sw.bb
+ i32 2, label %sw.bb
+ ]
+
+sw.bb: ; preds = %entry, %entry
+; CHECK-LABEL: sw.bb:
+; CHECK: %idxprom = sext i32 %i to i64
+; CHECK: %arrayidx = getelementptr inbounds i32, i32* %P, i64 %idxprom
+; CHECK: %0 = load i32, i32* %arrayidx, align 4
+ %add = add nsw i32 %0, %i
+ br label %sw.epilog
+
+sw.epilog: ; preds = %entry, %sw.bb
+ %sum.0 = phi i32 [ %add, %sw.bb ], [ 0, %entry ]
+ ret i32 %sum.0
+}