Make sure HoistInsertPosition finds a position that is dominated by all

inputs.

llvm-svn: 155809

2 files changed, 35 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 558b53332e3..c69abcb6409 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -4140,7 +4140,7 @@ LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
       // Attempt to find an insert position in the middle of the block,
       // instead of at the end, so that it can be used for other expansions.
       if (IDom == Inst->getParent() &&
-          (!BetterPos || DT.dominates(BetterPos, Inst)))
+          (!BetterPos || !DT.dominates(Inst, BetterPos)))
         BetterPos = llvm::next(BasicBlock::iterator(Inst));
     }
     if (!AllDominate)
diff --git a/llvm/test/Transforms/LoopStrengthReduce/pr12691.ll b/llvm/test/Transforms/LoopStrengthReduce/pr12691.ll
new file mode 100644
index 00000000000..8399434343e
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/pr12691.ll
@@ -0,0 +1,34 @@
+; RUN: opt < %s -loop-reduce -S | FileCheck %s
+
+@d = common global i32 0, align 4
+
+define void @fn2(i32 %x) nounwind uwtable {
+entry:
+  br label %for.cond
+
+for.cond:
+  %g.0 = phi i32 [ 0, %entry ], [ %dec, %for.cond ]
+  %tobool = icmp eq i32 %x, 0
+  %dec = add nsw i32 %g.0, -1
+  br i1 %tobool, label %for.cond, label %for.end
+
+for.end:
+; CHECK:  %tmp1 = load i32* @d, align 4
+; CHECK-NEXT:  %tmp2 = load i32* @d, align 4
+; CHECK-NEXT:  %0 = sub i32 %tmp1, %tmp2
+
+  %tmp1 = load i32* @d, align 4
+  %add = add nsw i32 %tmp1, %g.0
+  %tmp2 = load i32* @d, align 4
+  %tobool26 = icmp eq i32 %x, 0
+  br i1 %tobool26, label %for.end5, label %for.body.lr.ph
+
+for.body.lr.ph:
+  %tobool3 = icmp ne i32 %tmp2, %add
+  br label %for.end5
+
+for.end5:
+  ret void
+}
+
+