licm is wasting time hoisting constant foldable operations,
instead of hoisting them, just fold them away. This occurs in the
testcase for PR8041, for example.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112669 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index d3d52f5..fa71ab5 100644
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -36,11 +36,11 @@
#include "llvm/DerivedTypes.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Instructions.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AliasSetTracker.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Transforms/Utils/Local.h"
@@ -353,6 +353,18 @@
for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) {
Instruction &I = *II++;
+ // Try constant folding this instruction. If all the operands are
+ // constants, it is technically hoistable, but it would be better to just
+ // fold it.
+ if (Constant *C = ConstantFoldInstruction(&I)) {
+ DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *C << '\n');
+ CurAST->copyValue(&I, C);
+ CurAST->deleteValue(&I);
+ I.replaceAllUsesWith(C);
+ I.eraseFromParent();
+ continue;
+ }
+
// Try hoisting the instruction out to the preheader. We can only do this
// if all of the operands of the instruction are loop invariant and if it
// is safe to hoist the instruction.
@@ -360,7 +372,7 @@
if (isLoopInvariantInst(I) && canSinkOrHoistInst(I) &&
isSafeToExecuteUnconditionally(I))
hoist(I);
- }
+ }
const std::vector<DomTreeNode*> &Children = N->getChildren();
for (unsigned i = 0, e = Children.size(); i != e; ++i)