[llvm] r290728 - [LICM] Don't try to promote in loops where we have no chance to promote. NFC.

[Michael Kuperstein via llvm-commits]

Author: mkuper
Date: Thu Dec 29 16:51:22 2016
New Revision: 290728

URL: http://llvm.org/viewvc/llvm-project?rev=290728&view=rev
Log:
[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.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LICM.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=290728&r1=290727&r2=290728&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Thu Dec 29 16:51:22 2016
@@ -250,7 +250,12 @@ bool LoopInvariantCodeMotion::runOnLoop(
 
   // 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();