LICM does get dead instructions input to it. Instead of sinking them
out of loops, just delete them.
llvm-svn: 112451
diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 5f156db..aa842e3 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -43,6 +43,7 @@
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/CommandLine.h"
@@ -299,7 +300,7 @@
// If this subregion is not in the top level loop at all, exit.
if (!CurLoop->contains(BB)) return;
- // We are processing blocks in reverse dfo, so process children first...
+ // We are processing blocks in reverse dfo, so process children first.
const std::vector<DomTreeNode*> &Children = N->getChildren();
for (unsigned i = 0, e = Children.size(); i != e; ++i)
SinkRegion(Children[i]);
@@ -310,6 +311,16 @@
for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) {
Instruction &I = *--II;
+
+ // If the instruction is dead, we would try to sink it because it isn't used
+ // in the loop, instead, just delete it.
+ if (isInstructionTriviallyDead(&I)) {
+ ++II;
+ CurAST->deleteValue(&I);
+ I.eraseFromParent();
+ Changed = true;
+ continue;
+ }
// Check to see if we can sink this instruction to the exit blocks
// of the loop. We can do this if the all users of the instruction are