[PowerPC] Handle loop predecessor invokes

If a loop predecessor has an invoke as its terminator, and the return value
from that invoke is used to determine the loop iteration space, then we can't
insert a computation based on that value in the loop predecessor prior to the
terminator (oops). If there's such an invoke, or just no predecessor for that
matter, insert a new loop preheader.

llvm-svn: 228488

1 files changed, 12 insertions, 4 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp b/llvm/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp
index 76dbebc47bc..d370819d949 100644
--- a/llvm/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp
+++ b/llvm/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp
@@ -41,6 +41,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
 #include "llvm/Transforms/Utils/ValueMapper.h"
 using namespace llvm;
 
@@ -165,9 +166,6 @@ bool PPCLoopPreIncPrep::runOnLoop(Loop *L) {
     return MadeChange;
 
   BasicBlock *Header = L->getHeader();
-  BasicBlock *LoopPredecessor = L->getLoopPredecessor();
-  if (!LoopPredecessor)
-    return MadeChange;
 
   const PPCSubtarget *ST =
     TM ? TM->getSubtargetImpl(*Header->getParent()) : nullptr;
@@ -236,7 +234,17 @@ bool PPCLoopPreIncPrep::runOnLoop(Loop *L) {
     }
   }
 
-  if (Buckets.size() > MaxVars)
+  if (Buckets.empty() || Buckets.size() > MaxVars)
+    return MadeChange;
+
+  BasicBlock *LoopPredecessor = L->getLoopPredecessor();
+  // If there is no loop predecessor, or the loop predecessor's terminator
+  // returns a value (which might contribute to determining the loop's
+  // iteration space), insert a new preheader for the loop.
+  if (!LoopPredecessor ||
+      !LoopPredecessor->getTerminator()->getType()->isVoidTy())
+    LoopPredecessor = InsertPreheaderForLoop(L, this);
+  if (!LoopPredecessor)
     return MadeChange;
 
   SmallSet<BasicBlock *, 16> BBChanged;