[LICM] hoisting/sinking legality - bail early for unsupported instructions

Originally, this was part of a larger refactoring I'd planned, but had to abandoned.  I figured the minor improvement in readability was worthwhile.

llvm-svn: 338663

1 files changed, 19 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index c4ea43a4324..02e5839ff5b 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -575,10 +575,29 @@ static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT,
   return false;
 }
 
+namespace {
+/// Return true if-and-only-if we know how to (mechanically) both hoist and
+/// sink a given instruction out of a loop.  Does not address legality
+/// concerns such as aliasing or speculation safety.  
+bool isHoistableAndSinkableInst(Instruction &I) {
+  // Only these instructions are hoistable/sinkable.
+  return (isa<LoadInst>(I) || isa<CallInst>(I) ||
+          isa<BinaryOperator>(I) || isa<CastInst>(I) ||
+          isa<SelectInst>(I) || isa<GetElementPtrInst>(I) ||
+          isa<CmpInst>(I) || isa<InsertElementInst>(I) ||
+          isa<ExtractElementInst>(I) || isa<ShuffleVectorInst>(I) ||
+          isa<ExtractValueInst>(I) || isa<InsertValueInst>(I));
+}
+}
+
 bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
                               Loop *CurLoop, AliasSetTracker *CurAST,
                               LoopSafetyInfo *SafetyInfo,
                               OptimizationRemarkEmitter *ORE) {
+  // If we don't understand the instruction, bail early.
+  if (!isHoistableAndSinkableInst(I))
+    return false;
+  
   // SafetyInfo is nullptr if we are checking for sinking from preheader to
   // loop body.
   const bool SinkingToLoopBody = !SafetyInfo;
@@ -666,14 +685,6 @@ bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
     return false;
   }
 
-  // Only these instructions are hoistable/sinkable.
-  if (!isa<BinaryOperator>(I) && !isa<CastInst>(I) && !isa<SelectInst>(I) &&
-      !isa<GetElementPtrInst>(I) && !isa<CmpInst>(I) &&
-      !isa<InsertElementInst>(I) && !isa<ExtractElementInst>(I) &&
-      !isa<ShuffleVectorInst>(I) && !isa<ExtractValueInst>(I) &&
-      !isa<InsertValueInst>(I))
-    return false;
-
   // If we are checking for sinking from preheader to loop body it will be
   // always safe as there is no speculative execution.
   if (SinkingToLoopBody)