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-rw-r--r--contrib/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp208
1 files changed, 103 insertions, 105 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp
index 40d468a084d4..71859efbf4bd 100644
--- a/contrib/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp
+++ b/contrib/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp
@@ -20,8 +20,10 @@
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopIterator.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/DataLayout.h"
@@ -34,7 +36,6 @@
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include <algorithm>
#include <utility>
@@ -45,118 +46,116 @@ using namespace llvm;
STATISTIC(NumSimplified, "Number of redundant instructions simplified");
-static bool SimplifyLoopInst(Loop *L, DominatorTree *DT, LoopInfo *LI,
- AssumptionCache *AC,
- const TargetLibraryInfo *TLI) {
- SmallVector<BasicBlock *, 8> ExitBlocks;
- L->getUniqueExitBlocks(ExitBlocks);
- array_pod_sort(ExitBlocks.begin(), ExitBlocks.end());
-
+static bool simplifyLoopInst(Loop &L, DominatorTree &DT, LoopInfo &LI,
+ AssumptionCache &AC,
+ const TargetLibraryInfo &TLI) {
+ const DataLayout &DL = L.getHeader()->getModule()->getDataLayout();
+ SimplifyQuery SQ(DL, &TLI, &DT, &AC);
+
+ // On the first pass over the loop body we try to simplify every instruction.
+ // On subsequent passes, we can restrict this to only simplifying instructions
+ // where the inputs have been updated. We end up needing two sets: one
+ // containing the instructions we are simplifying in *this* pass, and one for
+ // the instructions we will want to simplify in the *next* pass. We use
+ // pointers so we can swap between two stably allocated sets.
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.
- using WorklistItem = PointerIntPair<BasicBlock *, 1>;
- SmallVector<WorklistItem, 16> VisitStack;
- SmallPtrSet<BasicBlock *, 32> Visited;
-
- bool Changed = false;
- bool LocalChanged;
- do {
- LocalChanged = false;
-
- VisitStack.clear();
- Visited.clear();
+ // Track the PHI nodes that have already been visited during each iteration so
+ // that we can identify when it is necessary to iterate.
+ SmallPtrSet<PHINode *, 4> VisitedPHIs;
- VisitStack.push_back(WorklistItem(L->getHeader(), false));
+ // While simplifying we may discover dead code or cause code to become dead.
+ // Keep track of all such instructions and we will delete them at the end.
+ SmallVector<Instruction *, 8> DeadInsts;
- while (!VisitStack.empty()) {
- WorklistItem Item = VisitStack.pop_back_val();
- BasicBlock *BB = Item.getPointer();
- bool IsSubloopHeader = Item.getInt();
- const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
+ // First we want to create an RPO traversal of the loop body. By processing in
+ // RPO we can ensure that definitions are processed prior to uses (for non PHI
+ // uses) in all cases. This ensures we maximize the simplifications in each
+ // iteration over the loop and minimizes the possible causes for continuing to
+ // iterate.
+ LoopBlocksRPO RPOT(&L);
+ RPOT.perform(&LI);
- // 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))
+ bool Changed = false;
+ for (;;) {
+ for (BasicBlock *BB : RPOT) {
+ for (Instruction &I : *BB) {
+ if (auto *PI = dyn_cast<PHINode>(&I))
+ VisitedPHIs.insert(PI);
+
+ if (I.use_empty()) {
+ if (isInstructionTriviallyDead(&I, &TLI))
+ DeadInsts.push_back(&I);
continue;
-
- // Don't bother simplifying unused instructions.
- if (!I->use_empty()) {
- Value *V = SimplifyInstruction(I, {DL, TLI, DT, AC});
- if (V && LI->replacementPreservesLCSSAForm(I, V)) {
- // Mark all uses for resimplification next time round the loop.
- for (User *U : I->users())
- Next->insert(cast<Instruction>(U));
-
- I->replaceAllUsesWith(V);
- LocalChanged = true;
- ++NumSimplified;
- }
- }
- if (RecursivelyDeleteTriviallyDeadInstructions(I, TLI)) {
- // RecursivelyDeleteTriviallyDeadInstruction can remove more than one
- // instruction, so simply incrementing the iterator does not work.
- // When instructions get deleted re-iterate instead.
- BI = BB->begin();
- BE = BB->end();
- LocalChanged = true;
}
- if (IsSubloopHeader && !isa<PHINode>(I))
- break;
- }
+ // We special case the first iteration which we can detect due to the
+ // empty `ToSimplify` set.
+ bool IsFirstIteration = ToSimplify->empty();
- // 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).second)
+ if (!IsFirstIteration && !ToSimplify->count(&I))
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).second)
- VisitStack.push_back(WorklistItem(ExitBB, false));
- }
-
+ Value *V = SimplifyInstruction(&I, SQ.getWithInstruction(&I));
+ if (!V || !LI.replacementPreservesLCSSAForm(&I, V))
continue;
- }
- bool IsExitBlock =
- std::binary_search(ExitBlocks.begin(), ExitBlocks.end(), SuccBB);
- if (IsExitBlock)
- continue;
+ for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
+ UI != UE;) {
+ Use &U = *UI++;
+ auto *UserI = cast<Instruction>(U.getUser());
+ U.set(V);
+
+ // If the instruction is used by a PHI node we have already processed
+ // we'll need to iterate on the loop body to converge, so add it to
+ // the next set.
+ if (auto *UserPI = dyn_cast<PHINode>(UserI))
+ if (VisitedPHIs.count(UserPI)) {
+ Next->insert(UserPI);
+ continue;
+ }
+
+ // If we are only simplifying targeted instructions and the user is an
+ // instruction in the loop body, add it to our set of targeted
+ // instructions. Because we process defs before uses (outside of PHIs)
+ // we won't have visited it yet.
+ //
+ // We also skip any uses outside of the loop being simplified. Those
+ // should always be PHI nodes due to LCSSA form, and we don't want to
+ // try to simplify those away.
+ assert((L.contains(UserI) || isa<PHINode>(UserI)) &&
+ "Uses outside the loop should be PHI nodes due to LCSSA!");
+ if (!IsFirstIteration && L.contains(UserI))
+ ToSimplify->insert(UserI);
+ }
- VisitStack.push_back(WorklistItem(SuccBB, false));
+ assert(I.use_empty() && "Should always have replaced all uses!");
+ if (isInstructionTriviallyDead(&I, &TLI))
+ DeadInsts.push_back(&I);
+ ++NumSimplified;
+ Changed = true;
}
}
- // Place the list of instructions to simplify on the next loop iteration
- // into ToSimplify.
- std::swap(ToSimplify, Next);
- Next->clear();
+ // Delete any dead instructions found thus far now that we've finished an
+ // iteration over all instructions in all the loop blocks.
+ if (!DeadInsts.empty()) {
+ Changed = true;
+ RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, &TLI);
+ }
+
+ // If we never found a PHI that needs to be simplified in the next
+ // iteration, we're done.
+ if (Next->empty())
+ break;
- Changed |= LocalChanged;
- } while (LocalChanged);
+ // Otherwise, put the next set in place for the next iteration and reset it
+ // and the visited PHIs for that iteration.
+ std::swap(Next, ToSimplify);
+ Next->clear();
+ VisitedPHIs.clear();
+ DeadInsts.clear();
+ }
return Changed;
}
@@ -174,21 +173,20 @@ public:
bool runOnLoop(Loop *L, LPPassManager &LPM) override {
if (skipLoop(L))
return false;
- DominatorTreeWrapperPass *DTWP =
- getAnalysisIfAvailable<DominatorTreeWrapperPass>();
- DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
- LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
- AssumptionCache *AC =
- &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(
+ DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+ AssumptionCache &AC =
+ getAnalysis<AssumptionCacheTracker>().getAssumptionCache(
*L->getHeader()->getParent());
- const TargetLibraryInfo *TLI =
- &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+ const TargetLibraryInfo &TLI =
+ getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
- return SimplifyLoopInst(L, DT, LI, AC, TLI);
+ return simplifyLoopInst(*L, DT, LI, AC, TLI);
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AssumptionCacheTracker>();
+ AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.setPreservesCFG();
getLoopAnalysisUsage(AU);
@@ -200,7 +198,7 @@ public:
PreservedAnalyses LoopInstSimplifyPass::run(Loop &L, LoopAnalysisManager &AM,
LoopStandardAnalysisResults &AR,
LPMUpdater &) {
- if (!SimplifyLoopInst(&L, &AR.DT, &AR.LI, &AR.AC, &AR.TLI))
+ if (!simplifyLoopInst(L, AR.DT, AR.LI, AR.AC, AR.TLI))
return PreservedAnalyses::all();
auto PA = getLoopPassPreservedAnalyses();
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-13 12:59:27 +0000