[LICM] Don't try to promote in loops where we have no chance to promote. NFC.

We would check whether we have a prehader *or* dedicated exit blocks,
and go into the promotion loop. Then, for each alias set we'd check
if we have a preheader *and* dedicated exit blocks, and bail if not.

Instead, bail immediately if we don't have both.

llvm-svn: 290728

1 files changed, 6 insertions, 10 deletions

diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 30a70379968..79dc103a774 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -250,7 +250,12 @@ bool LoopInvariantCodeMotion::runOnLoop(Loop *L, AliasAnalysis *AA,
 
   // Now that all loop invariants have been removed from the loop, promote any
   // memory references to scalars that we can.
-  if (!DisablePromotion && (Preheader || L->hasDedicatedExits())) {
+  // Don't sink stores from loops without dedicated block exits. Exits
+  // containing indirect branches are not transformed by loop simplify,
+  // make sure we catch that. An additional load may be generated in the
+  // preheader for SSA updater, so also avoid sinking when no preheader
+  // is available.
+  if (!DisablePromotion && Preheader && L->hasDedicatedExits()) {
     SmallVector<BasicBlock *, 8> ExitBlocks;
     SmallVector<Instruction *, 8> InsertPts;
     PredIteratorCache PIC;
@@ -909,15 +914,6 @@ bool llvm::promoteLoopAccessesToScalars(
   // us to prove better alignment.
   unsigned Alignment = 1;
   AAMDNodes AATags;
-  bool HasDedicatedExits = CurLoop->hasDedicatedExits();
-
-  // Don't sink stores from loops without dedicated block exits. Exits
-  // containing indirect branches are not transformed by loop simplify,
-  // make sure we catch that. An additional load may be generated in the
-  // preheader for SSA updater, so also avoid sinking when no preheader
-  // is available.
-  if (!HasDedicatedExits || !Preheader)
-    return false;
 
   const DataLayout &MDL = Preheader->getModule()->getDataLayout();