Sink: Don't sink static allocas from the entry block

CodeGen treats allocas outside the entry block as dynamically sized
stack objects.

llvm-svn: 204473

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/Sink.cpp b/llvm/lib/Transforms/Scalar/Sink.cpp
index 5e1e4564bba..41073749abc 100644
--- a/llvm/lib/Transforms/Scalar/Sink.cpp
+++ b/llvm/lib/Transforms/Scalar/Sink.cpp
@@ -216,6 +216,13 @@ bool Sinking::IsAcceptableTarget(Instruction *Inst,
 /// instruction out of its current block into a successor.
 bool Sinking::SinkInstruction(Instruction *Inst,
                               SmallPtrSet<Instruction *, 8> &Stores) {
+
+  // Don't sink static alloca instructions.  CodeGen assumes allocas outside the
+  // entry block are dynamically sized stack objects.
+  if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
+    if (AI->isStaticAlloca())
+      return false;
+
   // Check if it's safe to move the instruction.
   if (!isSafeToMove(Inst, AA, Stores))
     return false;