//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "loop-instsimplify"
+#include "llvm/Instructions.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
INITIALIZE_PASS_END(LoopInstSimplify, "loop-instsimplify",
"Simplify instructions in loops", false, false)
-Pass* llvm::createLoopInstSimplifyPass() {
+Pass *llvm::createLoopInstSimplifyPass() {
return new LoopInstSimplify();
}
L->getUniqueExitBlocks(ExitBlocks);
array_pod_sort(ExitBlocks.begin(), ExitBlocks.end());
- SmallVector<BasicBlock*, 16> VisitStack;
+ SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
+
+ // The bit we are stealing from the pointer represents whether this basic
+ // block is the header of a subloop, in which case we only process its phis.
+ typedef PointerIntPair<BasicBlock*, 1> WorklistItem;
+ SmallVector<WorklistItem, 16> VisitStack;
SmallPtrSet<BasicBlock*, 32> Visited;
bool Changed = false;
VisitStack.clear();
Visited.clear();
- VisitStack.push_back(L->getHeader());
+ VisitStack.push_back(WorklistItem(L->getHeader(), false));
while (!VisitStack.empty()) {
- BasicBlock *BB = VisitStack.back();
- VisitStack.pop_back();
+ WorklistItem Item = VisitStack.pop_back_val();
+ BasicBlock *BB = Item.getPointer();
+ bool IsSubloopHeader = Item.getInt();
// Simplify instructions in the current basic block.
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = BI++;
+
+ // The first time through the loop ToSimplify is empty and we try to
+ // simplify all instructions. On later iterations ToSimplify is not
+ // empty and we only bother simplifying instructions that are in it.
+ if (!ToSimplify->empty() && !ToSimplify->count(I))
+ continue;
+
// Don't bother simplifying unused instructions.
if (!I->use_empty()) {
Value *V = SimplifyInstruction(I, TD, DT);
if (V && LI->replacementPreservesLCSSAForm(I, V)) {
+ // Mark all uses for resimplification next time round the loop.
+ for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
+ UI != UE; ++UI)
+ Next->insert(cast<Instruction>(*UI));
+
I->replaceAllUsesWith(V);
LocalChanged = true;
++NumSimplified;
}
}
LocalChanged |= RecursivelyDeleteTriviallyDeadInstructions(I);
+
+ if (IsSubloopHeader && !isa<PHINode>(I))
+ break;
}
- // Add all successors to the worklist, except for loop exit blocks.
+ // Add all successors to the worklist, except for loop exit blocks and the
+ // bodies of subloops. We visit the headers of loops so that we can process
+ // their phis, but we contract the rest of the subloop body and only follow
+ // edges leading back to the original loop.
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
++SI) {
BasicBlock *SuccBB = *SI;
+ if (!Visited.insert(SuccBB))
+ continue;
+
+ const Loop *SuccLoop = LI->getLoopFor(SuccBB);
+ if (SuccLoop && SuccLoop->getHeader() == SuccBB
+ && L->contains(SuccLoop)) {
+ VisitStack.push_back(WorklistItem(SuccBB, true));
+
+ SmallVector<BasicBlock*, 8> SubLoopExitBlocks;
+ SuccLoop->getExitBlocks(SubLoopExitBlocks);
+
+ for (unsigned i = 0; i < SubLoopExitBlocks.size(); ++i) {
+ BasicBlock *ExitBB = SubLoopExitBlocks[i];
+ if (LI->getLoopFor(ExitBB) == L && Visited.insert(ExitBB))
+ VisitStack.push_back(WorklistItem(ExitBB, false));
+ }
+
+ continue;
+ }
+
bool IsExitBlock = std::binary_search(ExitBlocks.begin(),
- ExitBlocks.end(), SuccBB);
- if (!IsExitBlock && Visited.insert(SuccBB))
- VisitStack.push_back(SuccBB);
+ ExitBlocks.end(), SuccBB);
+ if (IsExitBlock)
+ continue;
+
+ VisitStack.push_back(WorklistItem(SuccBB, false));
}
}
+ // Place the list of instructions to simplify on the next loop iteration
+ // into ToSimplify.
+ std::swap(ToSimplify, Next);
+ Next->clear();
+
Changed |= LocalChanged;
} while (LocalChanged);